Condensation is unpleasant and unattractive and the mould growth as a result of it can have serious issues for our health, especially for people with breathing difficulties from asthma or other respiratory issues. It is an increasing problem as our homes used to be cold and drafty, which whilst not good for our comfort, pretty successfully prevented moisture from building up. However, as we keep our houses warmer and try to prevent drafts, it gives rise to problems with air circulation.

The reasons for it are usually pretty straight forward, and it should not be an insurmountable issue in any house. First, bear in mind that our houses are constantly producing moisture which needs to go somewhere. An average 4 person household will produce a staggering 112 pints of moisture a week from a combination of cooking, showers, boiling the kettle and just breathing!

If we are going to try to avoid it there are just a few things we need to remember.

1. Temperature. Warm air holds more moisture than cold air. When warm air cools or comes into contact with a cold surface, the water will condense and settle on the cold surface.
2. Ventilation. Moving air carries away moisture. This is why a breeze cools us down and fans help in an environment with high humility.
3. Humidity. The dew point of air (the temperature at which water condenses) reduces as humidity decreases, so if you can reduce the water content in the air, it is less likely to condense on a surface.

Bearing these basic principles in mind there are a number of things we can do to reduce the risk of condensation in a house. They all break down into a combination of lifestyle, passive and active fixes. The first two tend to prevent the build up of moisture in the first place and the third deals with the problem once it has occurred. If a lifestyle fix can be used, it is always preferable because it doesn’t cost anything, and a passive fix has a one-time rather than ongoing costs so is preferable to an active one. The problem with the active solutions is that they don’t deal with the root cause but just the symptoms, and so should be less of a priority.

Lifestyle fixes

1 – Heat the house consistently. Keep the whole house at a similar temperature, so that water vapour which is absorbed into the air in the living room doesn’t pass into the bathroom and condense on the surfaces in there.

2 – Heat the house continuously. Try to keep the house at a fairly stable temperature. Keep the thermostat at 15 while you are out so that the building doesn’t cool down dramatically, because this leads to the water in the air condensing and then evaporating when the heating comes on again. Keeping the air at a high enough temperature will physically prevent the moisture in the air from condensing on surfaces. It also means that the building warms up quickly when you get home!

3 – Cover pots when cooking. This will save on the gas or electricity needed to heat your vegetables and cook them quicker because the water gets hotter and they steam a little. Tests show that a pan boils in 4 minutes and 15 seconds with the lid on and 4 minutes and 45 seconds with the lid off. Not a big saving notably, but over a period of time it will save money and time. Families who do a lot of cooking can have significant issues with this.

4 – Dry clothes in a separate room. If possible, dry clothes in a dedicated room and leave the window open while the clothes are drying, or just open them intermittently to let out the moist air without wasting too much heat.

5 – Separate the utility room from the kitchen. Put the washing machine and tumble dryer in a separate room with its own extractor fan and keep the door closed when in use so that the moisture doesn’t get into the rest of the house.

6 – Open windows in good weather and close curtains at night. Get rid of the stale, damp air every now and then by opening the windows when the weather permits. This gets rid of all the moisture which is stuck inside. Also remember to close the curtains at night to keep the heat in and so stop the house from cooling down at night. Thick or lined curtains are the best, although you can also get insulated blinds which are shaped like a fan. All of these help keep the house warmer.

Passive fixes

7 – Seal up gaps around windows and doors. Increase the internal temperature by sealing up gaps prevents drafts. This will also save you money on your heating bills. Seal them from the outside with mastic sealant between the window and the wall, and from the inside with a strip of sticky-backed foam to make the joints in your windows more air-tight.

8 – Install trickle ventilation. Increase natural ventilation in your home by installing trickle ventilators in the windows and doors. These can be retro-fitted into the frame of a UPVC window, and are essentially a few holes drilled in the plastic frame, with cover plates on the inside and out. They are not the most attractive things, but are cheap, at around £4 each and can provide some much-needed ventilation. These are not as good as windows which have them pre-installed, but they are a lot better than nothing.

9 – Undercut your doors. Improve natural ventilation throughout your house by cutting a little off the bottom of the doors to allow air to move around the house more freely, and prevent moisture from building up in any particular area. A 10-15mm gap between the underside of the door and the floor finish is ideal.

10 – Use absorbent materials. Salt or water-retaining crystals can be placed in bowls to absorb the moisture from the air. They can be placed on window sills where the condensation is most likely to occur, and bear in mind that they need to be periodically emptied so that they can carry on being effective.

11 – Improve insulation. Increase the internal temperature by adding insulation to your home. This can be added to the walls, roofs and floors and will help keep your home warm. Refer to the article on Insulating Your Home which gives more detail on the options for doing this.

12 – Install double glazing. This also helps increase internal temperature, and the two layers of glazing reduce the temperature differential between the two sides of the glass which means that moisture is less likely to condense on the surface. Make sure that the windows have trickle vents installed!

13 – Vent a tumble dryer. Make sure that a tumble dryer is vented to the outside air if it is designed to be used with one. Ideally these should be located against an external wall and duct straight to the outside, but they can be ducted through the house in a similar way to an extractor fan, or you can buy a condenser which connects to the end of a duct which collects the condensate (available from most DIY stores) but they are not recommended by the manufacturers because they are not always effective and can still lead to significant moisture build-up, but they are used widely and are a cheap and convenient solution to a problem (all be it not a long term solution) and the strictly correct method can be complex and expensive.

Whilst long ducts for extractor fans are common, they are more of an issue with dryers as the air from a tumble dryer tends to be carrying lint with the expelled air which can settle in the pipe over time. You should firstly consult the manufacturer’s literature to see the maximum duct length for the design of your vent, i.e. with the number of bends needed for your installation. It should also be possible to clean the duct occasionally (probably once a year for a domestic installation). Then decide whether you are going to use flexible or rigid metal ducting, as rigid ducting allows longer ducts to be used because it has no ribs for the lint to collect on. Whilst plastic ducting is smooth and so should suit dryer ducting, it tends to have a static charge which leads to lint collecting on the inside of the pipe. If you have serious issues, you can also install a pump into the route of the duct to force the air through at a higher pressure.

Active fixes

14 – Buy a hygrometer. These are a cheap way to monitor the level of humidity in the home, so that you can see when you need to take action. You should try to keep the humidity level 50%, and run extractor fans to remove the humidity levels when they rise above this. At around £20 they are good value, and let you know the extent of the problem.

15 – Use extractor fans and hoods. These remove air from the areas where it is most likely to be damp, i.e. the kitchen and bathroom, and prevent it from moving into the rest of the house. Set the overrun to be 15-20 minutes after the light is switched off rather than the standard 5. If you have a kitchen or bathroom without a working extractor fan, then it does not meet building regulations at the moment, and installing or replacing one can be a good idea. At £20 for a basic model, these are a great way to get rid of unwanted humidity and smells.

16 – Upgrade your extractor fan to one with a humidistat. These monitor the humidity in the air and only turn off when it has been reduced to a suitable level. These are more precise than a simple timer overrun, although they can be quite a lot more expensive. There are also issues reported with the reliability of the humidistats, meaning that a lot comes down to the setup, as they can be set to run too long or not enough. These cost around £40, so are a good value solution.

17 – Upgrade your extractor fan to a dMEV unit. This stands for a decentralised Mechanical Extract Ventilation unit. As modern houses are increasingly airtight, there is an increasing concern over air quality, and if unventilated, carbon dioxide levels rise significantly, especially over winter. These provide a constant extraction of air at a much slower rate than a standard extractor fan, with a boost for when they are needed (i.e. activated by the light). They run very efficiently and so have a minimal cost, (around £4 per year) and are silent in low power mode so that the noise does not become a nuisance. These cost around £120, which whilst being significantly more expensive than a standard model, are a lot cheaper than a full MVHR system. Combining this with undercutting the doors allows the whole house to benefit from this continuous background ventilation.

18 – Dehumidifier. Dehumidifiers take the moisture out of the air by passing the air over a cold element so that the water condenses on it, and the heat is expelled back into the room. As you can imagine, these are expensive to run because they use a similar amount of electricity to an air conditioner. In actual fact, the only difference between an air conditioner and a dehumidifier is that the warm air from an air conditioner is discharged outside to cool the room down, whereas a dehumidifier discharges the heat back into the room so that there is no change in air temperature. In this way they are a short term fix, suitable for use on a building site where you have a large amount of air to get rid of at one point in time, but if the moisture build-up is constant, something more fundamental needs to be done.

19 – MVHR (Mechanical Ventilation with Heat Recovery). The most expensive solution is a whole house ventilation system, costing £3-4,000. This provides extraction and supply and a heat exchanger makes a very efficient heat transfer from the outgoing to the incoming air, so that they can be a great part of a sustainability strategy for a house, but they  rely on the house being highly airtight and insulated before it would deliver energy savings (an air tightness level of 3 air changes per hour would be sufficient). It definitely doesn’t make sense to install one primarily as a means to deal with condensation.

20 – Last resort. Sell one of your children. This will reduce the humidity levels and help with the finances as well!

The post Preventing condensation: 20 ways to stop it & why it happens first appeared on Archi-HOUSE.

Clean fuel

The first thing has to be to use a sustainable fuel to provide the heat which is needed to heat the house. Wood is a clean source of energy, because when it burns it only releases the carbon it absorbed during it’s lifetime, which makes it a nett zero carbon fuel. This can take the form of an attractive wood burning stove in your living room, and if you want this to provide hot water as well it can include a back boiler, or you can go for a fully fledged wood boiler which provides the central heating for your whole house, which loads itself and does not need to be loaded manually.

Wood burning stoves

A wood burning stove is the easiest and simplest way to take advantage of some zero carbon heat for your home. They cost £2-3,000 and are quite a straight forward addition to any home. The only thing which you need to be careful about is the proximity of the flue to windows or rooflights, so that the smoke from the flue does not go straight back into an open window.

These are a very cosy way to provide a boost to your heating system on a cold winter’s night. An issue can be that they churn out too much heat. If the house is otherwise well-insulated, the heating load for the whole house would be around 6kW for a 200m2 house built to current standards. Given that wood burning stoves are generally rated from 5-20kW they can very quickly make a well-insulated house swelteringly hot!

The beauty of them as opposed to open fires is that they burn the wood much more efficiently because they burn the wood at a much higher temperature, and they have a sealed air intake and flue which is closed off from the house so that they do not cause draughts. This makes them much more suitable for modern, air-tight Eco-houses. The downside however is that they need to manually loaded and lit each time they are needed.

Biomass boilers

These are a step up from a wood burner, and generally burn wood pellets, but larger ones can be used which burn wood chip & logs or peat, coke and coal can be burned on multi-fuel burners. They cost a minimum of £10,000, and cost around £100/year more than gas so there are no financial benefits unless your central heating currently runs on oil. Unless of course you have access to your own source of wood!

They are generally much larger than a wood burner, being a couple of feet square and four to five feet tall, with an accompanying pellet store from where the pellets are fed into the burner. They also look pretty functional so are more suitable for the garage than a corner of the living room. They also need a dedicated fuel supply which will take up a few square feet of floor space as well. Either way, due to the sheer quantities of fuel this is not going to be a carefully stacked Scandinavian wood-pile.

Wood pellets are the best fuel because they are designed to burn efficiently with a high surface area, and they are small and move almost like a liquid which makes them suitable for mechanical loaders such as augers. Whilst it cannot be argued that they are cheap to install, they provide a carbon neutral central heating and hot water system, and the RHI of around £1000/year would achieve payback in 12 years.

Passive solar gain

Free energy is always popular, and in the UK any south-facing window will gain more heat from the sun than it loses over the year, meaning that it is free heat for your house. So maximising the number and size of windows on the south side of your house will lower heating bills. They also have the benefit of increasing natural light daylight and views, which doubly improves the atmosphere of a house. Ideally this should be combined with a solid, heat-retaining material on the floor such as a tiled floor or concrete, which ensures that the heat is absorbed and will be emitted after the sun has gone down. The technical term is a material with a high thermal mass, i.e. it heats up and cools down slowly.

Windows should always have blinds and curtains on the inside to reduce heat loss at night and in winter, but these are used in most houses. Also, it is always possible to have too much of a good thing (see below) so you should moderate the amount of glazing, otherwise you can suffer from serious over-heating in the summer. I can also imagine it being a nightmare closing all the blinds in this house at night to prevent heat loss in the winter!

Reducing water consumption

We can all reduce our water consumption by using low flow-rate taps and showers, and WC’s with dual flushes. This is built into the building regulations now, so that they are no longer optional, but a requirement. There are also behavioural changes which we can make to reduce our water consumption. These tips are down to Water-wise.

• Install dual flushes which use 4-6 litres per flush as opposed to the traditional ones 13 litres per flush!
• A cistern displacement device (CDD) is a very simple way to further reduce the water consumption of your flus (by about 1 litre per flush).
• Toilet flushing accounts for 30% of water consumption. Don’t flush cotton wool or make-up tissues down the toilet, but put them in the bin.
• While brushing your teeth only run the tap while washing your brush or mouth! We waste 6 litres per minute with a running tap.
• Low flow or aerated shower heads reduce water consumption while giving the feeling of more water through pressure or air in the water.
• Reduce the length of your showers by using a shower timer!
• Baths typically use 80 litres of water (3 times the amount of showers) so shower more than you bathe!
• Use a full load in your dishwasher and washing machine to maximise the efficiency of every wash.
• Use an aerator on the tap in the kitchen and bathroom sink to reduce the flow rate.
• Put the lid on saucepans while they boil. This will mean that they lose less water through steam and the veggies boil quicker!

Sustainable Urban Drainage Systems (SUDS)

The fact is that annual rainfall is going up every year as a result of global warming. The facts are not in doubt, it is just a case of whether the cause is man-made or natural. In the case of domestic projects your impact will be small, but if you want to do your bit there is always something you can do.

Impermeable surfaces such as paving and tarmac need to be drained, so reducing the extent of the site given over to these reduces rainwater run-off. These surfaces can also drain to a planted area on the site instead of a drain which again prevents the water from going into the drains, as shown in the image below. Permeable paving is also an alternative, as it allows the water to pass through the surface and into the soil below.

A simple soakaway for your home can be made by connecting the rainwater pipes from your house into a gravel strip with a land drain in the bottom. The gravel strips allows the water to sit around for a time before going into the drain which gives a chance for the ground to absorb the water, whilst the drain ensures that the water will always goes down the drain before it has a chance to flood your garden! 

Increasing environmental habitat

The increasing area of our cities which are covered in hard surfaces also reduces the space for animals, birds and insects to feed and live. Most of us would like to see more wildlife in our cities, and so creating spaces for nature can give people a great connection to nature. We can take action on many levels.

• Plant flowers which attract insects, like salvia, redbeckia, lavender and nepeta
• Put out bird feeders and a nesting box.
• Build a wood pile for hibernating hedgehogs
• Dig a pond as a habitat for plants, amphibians and fish, which is probably the best single habitat. Use straw to keep the water clean naturally.
• Ponds should have a shallow area for access by frogs and newts and tall plants for animals to hide in.
• Start a compost heap. It creates natural fertiliser for free and is also a habitat for small creatures.
• Don’t make it too tidy, allow some areas to get overgrown to allow animals to hide.
• Plant a wildflower meadow (a combination of grasses and flowers). These are a great habitat for insects and low maintenance, which are steeply on the decline in the UK, having lost 96% since the 1950’s.
• Create a rock garden, which is a specialised habitat for different plants and animals.

Some cities are taking more serious steps in their architecture. Berlin and Malmo require that 50% of the area of any new development should be a bio-diverse landscape which can be used by birds and insects. As you can imagine this is a pretty challenging requirement, which has led to the green roof-scape of these cities.

The post Eco-Minimalism: Going beyond the envelope first appeared on Archi-HOUSE.

As mentioned previously, heating accounts for 60% of the energy consumption of a house, with the other 40% going on all the electrical appliances, including washing machines, TV’s and computers. So before we resort to renewable sources for the electricity we use, we should minimise the energy that we need to heat our homes.

Heat loss happens in three principle ways, through the fabric of the building itself, through gaps in the fabric and through weak points. In clothing these are comparable to the jumper you wear when it’s getting chilly, the jacket you put on when it’s getting that bit windy as well, and the hat and gloves you were when it’s seriously cold. The insulation manufacturer Isover recently did a study and found out that 60% of the heat loss is through the key building elements, with 30% going to air-tightness and 10% to thermal bridging. In this way, insulation is the priority, then air-tightness and then thermal bridging.

Insulation

So the main fabric of your house needs to be insulated so that the walls, floors and roof lose less heat. The diagram below shows the heat loss from a typical house, and although very general, it gives an idea of the heat loss in a house in relation to the different elements, which gives us an idea of how to prioritise the areas which most need insulation. The greatest heat loss is through the walls, with the roof a close second, and the floor and windows being less of a priority (I have ignored doors as this is really air-tightness which is a separate issue). We can then look at a cost:return payoff for each element to see where the budget should be allocated, for instance loft insulation is very cheap and is usually straight forward to install and so is a no-brainer whereas double glazing will have a much smaller impact on heat loss.

The easy solutions

The easiest solutions is to insulate your loft which will only cost you a couple of hundred pounds.

If you have a suspended timber floor you can lay mineral wool between the joists with a net below to hold the insulation in place. This can be done for a couple of hundred pounds as well.

Cavity wall insulation is the next priority, because it will cost around £500, although you will need specialists to install it.

Double glazing can cost £5,000 for UPVc and a lot more for timber or aluminium, but these will still have a significant impact on heat loss. Even in a solid-walled flat, replacing the old windows for double glazing has a significant impact on reducing heat loss, and can make the difference between an uncomfortable environment in winter to a very warm one.

Traditional construction

Insulation is more complex when your house is a traditional construction, with solid brick or stone walls which needs internal or external wall insulation. This can cost £10-15,000 for internal insulation and £15-20,000 for eternal, and both are more intrusive. External insulation changes the look of your house, and internal insulation impacts on the use of your house. However, if they have not been carried out they will have the most significant impact on heat loss from your house.

Concrete floors are the most difficult to insulate because you have to raise the level of the ground floor. This has an impact on the internal floor level and stairs, needing steps and ramps to get around them, and all the doors will need to be altered. It would be very unusual to do this in all but the most extensive refurbishment projects.

Building regulations

The current Scottish Building regulations apply differently to a new-build house and an extension. A new-build house should achieve a u-value of 0.22 in walls, 0.18 in floors, and 0.15 in roofs, with windows achieving 1.6. In an extension, if the existing building is un-insulated, then significantly more onerous u-values apply, (0.17 for walls, 0.15 for floors & 0.11-0.13 for roofs, with windows required to achieve 1.4) whereas if the building is insulated (i.e. with cavity wall insulation etc) then the same u-values apply as for new-build. Although quite easy to achieve, the SAP calculation for a new-build house means that in practice, you will have to significantly improve on these values, or put a lot of solar panels etc on your building to bring it up to scratch, although an extension just needs to meet these minimum values.

Air tightness

Preventing air leakage from all the small gaps in a building’s construction is the next priority. This takes the form of an airtight material, which could be cast concrete, glass, plaster, plastic, or thick OSB. A concrete floor is inherently air-tight so it does not need a separate air-tight layer, but blockwork and timber are not air-tight so they do. In timber kit a plastic-type sheet is used (VCL) and in blockwork a coat of plaster is used (parge coat).

It is important that the air-tight layer is continuous, or else it fails to achieve it’s aim of air-tightness, so when a VCL is used it is important that all the sheets are taped at joints and at junctions with windows, doors, ceilings and floors. If looking at a cross section of a building, you should be able to trace the continuous line of air-tightness on the building without lifting your pen from the page.

The building regulations currently require quite a low target for air-tightness (around 10 air changes per hour) but as the SAP calculations get more onerous this is having to be improved. A typical modern house in Scotland with well-detailed air-tightness will achieve around 5 air changes per hour and flats often achieve 4. The average in England is still around 7 which is a result of the less onerous requirements. In contrast a traditionally-built houses will expect to achieve around 20 air changes per hour, which shows you just how much heated air is being lost.

Thermal bridging

The final piece of the puzzle is thermal bridging. Until recently this has not been considered a major issue, and was not essential. However, since the introduction of the 2015 building regulations we have had to pay attention to this. We cannot rely on the insulation within the timber kit any more, but need to apply a thin sheet of insulation to the inside face of the timber kit as well as into the window reveal to stop heat leaking out at the locations of solid timber structure.

This has been brought about through the gradually increasing requirements in terms of energy efficiency. Accredited details were introduced in Scotland a while ago, as a guarantee of a certain level of performance. As the technical requirements became more onerous, it became necessary to use these details, to the extent where even the most ardent speculative house builders who did their best to avoid the additional cost of the materials required, consented and started to build using these details.

The main change is the installation of a thin strip of insulation board across the whole face of the timber kit to prevent the heat passing through the solid timber structure, but all the specific details also need this insulation to be applied, i.e. the window and door heads and jambs (sides) The insulation needs to be of a certain performance, i.e. PIR rather than EPS or similar.There are similar details for block-work houses.

This additional insulation has the added bonus of preventing condensation within your house. Condensation occurs where warm, moist air comes into contact with a cold surface causing the water within the air to condense, so it is liable to occur where the structure is un-insulated, i.e. around your window and doors. A thin layer of insulation in these areas prevents this.

Mechanical Ventilation with Heat Recovery (MVHR)

This drive towards warmer and more air-tight homes does create a new issue which was unheard of in traditionally-built homes, which is that or air quality. Buildings always inherently allowed air (and heat) to pass through relatively easily, but the prevention of air movement can lead to the build-up of smells and generally stale air. This can be a particularly issue in winter when the windows are not opened. We also continually replace the Oxygen in the air around us with CO2, which needs to be allowed to escape and be replaced with oxygen rich air. Whilst there is not any danger of suffocation in a modern home, as no house can be made that air-tight, this does need to be avoided, and ideally without opening the windows and letting out all that carefully heated air!

The solution is MVHR. This extracts the warm stale air from the kitchen and bathrooms, and draws in cold dry air from outside. It passes the two streams of air very close to each other so that 90% of the heat is transferred from the outgoing to the incoming air. This can be done with over 90% efficiency with modern units. A mechanical system is not generally required unless a high level of air-tightness has been achieved, and it is generally accepted that 3 air changes is the cut-off for these being required. This is also generally viewed as the point at which MVHR becomes efficient in terms of paying for itself because if the air-tightness is any less then it is a waste to have an electric system trying to do heat exchange on extract air when it is leaking out all over the building in an uncontrolled way.

Passivhaus

The logical conclusion of this drive for preventing heat loss is building a house which is so efficient that it has no need for a central heating system at all. A German and a Swedish scientist thought that this was possible so set up a set of standards which would make central heating obsolete. This is a complex set of spreadsheets taking account of everything from the orientation of your windows, the insulation in your walls, to the size of the window frames and the amount of over-shadowing from trees. There might seem like a vast amount of data required, but the result is a mathematical model which can accurately predict the energy use of your heating system, and the internal temperature, from the coldest day in winter to the hottest day in summer. It even tells you if you will need to open the windows in summer because it gets too hot.

This is a lot more complicated than a SAP Calculation, so it is a lot more complicated than purely minimum U-values, but these are a part of it. Walls, Floors and Roofs all generally need to achieve as close to 0.10 as possible. All the details need to be designed (and mathematically modelled!) to minimise heat loss, and a stonking air-tightness of 0.6 air changes/hour needs to be achieved. A super-efficient MVHR system needs to be added as well as usually triple glazing. You also need to minimise the number of windows on the north side of the building (as these lose heat over a year) or else you will need to increase the insulation elsewhere in compensation.

A lot of these have been built, but they have mainly been in German-speaking Europe (Germany and Austria) where there are 20-30,000, and there are still only a handful in the UK, although they are getting increasingly popular. The best thing about the Passivhaus standard for us as designers is that it doesn’t enforce a particular style or construction method on the Home-owner or Architect, it just sets out a set of standards, and it is up to you how this is achieved. This is the gold standard in sustainable housing design, however it is not easy to achieve. The design team (and ideally the builder as well) need to have experience in this form of construction, because it is a complete shift in mindset. Everything is affected by the drive for heat loss. No more standard specification documents! Any consultant taking on one of these projects is likely to have to devote double the usual time to it, so that they can re-assess every part of what they do to meet the stringent requirements of the standard.

The image above is of a Passivhaus designed by Bere:Architects. It is both a Passivhaus and a Zeo Carbon house, meaning that not content with ultra-low heating bills, they also wanted to generate their own hot water and electricity, which has to make it the ultimate Eco-House!

Unfortunately all this does not come cheap. Passivhaus-accredited windows cost double what standard windows cost. The extra insulation (generally about a foot thick) is a significant expense, as well as the accredited MVHR system. All of these together mean that the cost of building to the Passivhaus standard increases the build cost by around 15%. For a £150,000 house, this would be an extra £22,500, which is not far off the cost of some renewable technologies, and the reward of a yearly fuel bill under £100 is an enviable reward! This could amount to a saving of 500/year compared a house built to current standards, which is easily the greatest saving compared to any other renewable technology. However, the downside is that it does not qualify for the RHI, which means that the payback period is not very inspiring at around 45 years. This is frustrating for those who believe that this is the future of sustainable design, and we hope that the government will change their position on this soon.

However, there are other ways to look at it which improve the apparent savings of achieving Passivhaus. Firstly, if we assume that the price of fuel continues to rise at the rate above inflation that is is at the moment (around 6% a year) then the savings will be far more enviable in 25 years. We can also consider the impact of taking the savings off the effective mortgage repayments, i.e. if that £500/year saving was spent on the mortgage, it would but you an extra £8,000 in capital borrowing across the lifetime of the mortgage, so you could take this off your effective expenditure, which reduces the £22,500 spend to £14,500, which is comparable to the other renewable technologies. However, Passivhaus won’t break down, gradually reduce in performance or suffer from a change in government funding priorities. In Germany the government offer a low interest loan to cover the additional cost of a Passivhaus, which can be paid off like a mortgage, which might encourage the take-up of the standard in the UK.

So, if I was asked my professional opinion on what is the best way to make your building sustainable, and you had a budget of £15-20,000, I would say it has to be to build a Passivhaus. It addresses all of the issues raised above and does it all to a very high standard. Unfortunately this is a significant investment for anyone, and financial limitations mean that although this is the ideal, most of us will have to settle somewhere along the way.

The first steps to getting an Eco-House are to make sure that the essentials are in place, insulation, air-tightness and thermal bridging, and if the level of air-tightness warrants it, then MVHR would be the technology to use. After this there are a variety of other things which can be done. Refer to my next post for these.

Eco-Minimalism: Going beyond the envelope

The post The main aim of Eco-Minimalism: Reduce heat loss first appeared on Archi-HOUSE.

After having carried out all of these measures, the only solution is to then generate electricity from renewable sources. The key issue with this is that it relies on expensive equipment which has a limited shelf life and deteriorates over time, and so the only way that it can be made to stack up financially is through government subsidy (the RHI), without which these products would never achieve a payback before they needed to be replaced. However, government funding has been set up to encourage the implimentation of these strategies, so there is certainly a financial incentive.

The options outlined below describe the strategies available. Solar panels and wind turbines provide electricity from a renewable source and heat pumps make more efficient use of this electricity once it has been generated.

There are also strategies which do not have the clear and direct impact on the costs of running our homes which are a stronger motivation for a lot of people, but they may be considered by homeowners who are concerned about reducing their impact on the environment. Some of them have complications with their implimentation (which are highlighted below), but they will always have a positive impact on the sustainability of the dwelling.

Our cities are increasingly covered in concrete, tarmac, and other hard surfaces, meaning that the rainwater which used to naturally soaked into the soil now runs straight into the drains all at once, creating a storm-water surge in rivers downstream. Reducing the rainwater run-off from a housing development is an increasingly onerous task as the Utility companies place higher requirements on the builders to ensure that the systems which are already over-loaded are not stretched to breaking point. Every new housing development has large tanks which hold the rainwater back so that it does not flow at once into the sewer system. Although not required by regulations, you can do your bit to reduce the impact of this by taking efforts to reduce the impact of rainwater running off your site by holding it on the site – Green Roofs & Sustainable Urban Drainage Systems (SUD’s) or recycling it – Rain-Water Harvesting (RWH).

Solar panels (Thermal and PV)

Pros

• 12-23 year payback
• Relatively expensive

Cons

• Design life of 25 years
• Reduction in performance of 1% per year

These can take the form of photo-voltaics (PV) which produce electricity, or thermal panels which pre-heat the water supply. They can be installed on most roofs, but work best facing south, or between south-east and south-west. They can be fixed to the outside of you roof (with the tiles or slates below), or built into the roof (i.e. flush with the tiles) or you can use solar tiles for the roof. The second two are more expensive than the simplest solution which is to put it on the outside, and makes repair or replacement a lot simpler 25 years down the line.

A thermal system will cost £3-5,000 for a 4sqm system, and a PV system will cost £5-8,000 for a 4kW system. A solar thermal system will pay back £330/year and a PV system will pay back £280/year and so they achieve payback in 12 & 23 years consecutively. Whilst the cost of these systems has come down a lot in recent years, there has also been a drop in the government subsidy offered to them (the RHI) and so they still take some time to achieve payback, bearing in mind that it is only after this that you are getting free energy, you will be waiting a long time for a return on your investment.

These systems also have a design life of 25 years so they will need to be replaced at some point, and they gradually lose performance with their efficiency dropping by around 1% per year (which simple payback calculations do not take into account).

Green Roofs

Pros

• Attractive feature
• Natural habitat
• Reduces drainage requirement

Cons

• Expensive to install
• Structure needs reinforcement
• No financial incentive

These can be intensive or extensive. Extensive roofs have less than 6 inches of soil and so weigh less, and will have reduced watering and maintenance requirements, but due to the depth of soil the planting options are limited to water retaining plants such as sedum. Intensive roofs hold more water and so weigh more, but can be planted with a much wider range of plants. These make an attractive roof to look out over, especially if they are predominantly seen from above, and they need to be relatively flat to retain the soil on them.

They can form a part of a sustainable drainage system by reducing the rainwater run-off from buildings. Storm water surges are an increasing issue, and large projects have to install large tanks to reduce rainwater run-off, and it is getting more onerous every year with the statistics (which prove global warming). The soil retains the water which falls on it so that it doesn’t go straight into the rainwater pipes and into the drains, which will have a beneficial impact on your local sewer network. And it also creates a small habitat for wildlife, especially insects and butterflies which struggle to find space in our cities which are increasingly concreted over. In this way a green roof makes particular sense in an inner city environment where the issues of habitat and rainwater run-off are more critical and especially if they can be combined with an accessible roof garden which is enjoyed by people.

However, they are expensive to build, adding to the water-proofing needed and the structural requirements of the roof. You will need a specialist waterproofing system to make sure that there are no leaks, and your Structural Engineer will likely need to increase the size of his structure to accommodate the weight of the system (particularly if you go for a more attractive intensive roof). There is also no chance of being rewarded financially for your choice because there is no funding or subsidy for this.

Wind turbines

Pros

• Simple, bolt-on technology
• Small ones can be wall-mounted
• Large ones can produce significant amounts of electricity

Cons

• Expensive to install
• Can be noisy and unpopular with neighbours
• Low energy generation in most urban sites

Wind turbines come in varied sizes from Micro – around 1kW to Small – 2.5kW and Medium – 6kW. The Micro-type can be mounted on the side of a house, although the performance of these is significantly reduced because of the turbulence caused by the roof itself. In terms of domestic-sized turbines the diameter of the blades is roughly equivalent to the rating of the turbine, i.e. Micro will have 1 metre diameter rotors and Medium will have 5.5m wide rotors. The electrical current is produced in DC form, so it needs to be converted to AC with an inverter.

The cost is around £2,000 for a Micro turbine, £15,000 for a small turbine and £30,000 for a medium turbine. The rating of the turbine (measured in kW) is not a measure of expected electricity production, but tested production at a consistent wind speed of 12 m/s. Bearing in mind that this is 30 mph and the average wind speed in the UK is 5.6 m/s and you can see that the rating is substantially more than will be achieved unless you have a very windy site!

Which magazine recently undertook a test of a basic 1kW turbine and found that it used more energy than it generated, because the inverter uses power constantly whether the turbine is running or not! They can also be noisy, generating a sound from the rotors through the air as  well as vibrations, which can be deemed a nuisance by passers-by and neighbours. Also, a planning requirement for wind turbines is that they are located the height of the wind turbine + 10% from any site boundary, which in itself is likely to makes them impossible for most urban sites.

However, if there is space for a large turbine, and your site is suitable, they can generate significant amounts of energy.

Rainwater harvesting (RWH)

Pros

• Effectively reduce water consumption
• Reduce run-off into public sewer network
• Can be used on any site

Cons

• No financial incentive

These involve collecting the rainwater from the roof of your house in storage tanks and recycling it for purposes other than drinking, such as watering the garden, flushing toilets & supplying washing machines. The tanks are generally underground from where the water is pumped back up to the level of the bathrooms or kitchen. There are variations which store the water in tanks in the roof eaves, but the size of these is limited by the strength of the ceiling rafters and so the capacity is significantly reduced.

They typically cost £2-4,000, but there is little to no way to get repaid for your investment. In England, water consumption is not usually metered, but if it is you can save some money. In Scotland, however the Water rates are included with the Council Tax so there is no way to avoid them. This may make sense in a location where the water supply is not good or consistent, i.e. it may rely on a stream rather than mains water, in which case minimising your water consumption may be more of a priority.

A simple and economic system which is not quite as glamorous is to install a rainwater butt for watering the garden to get you around a hosepipe ban.

Greywater recycling

Pros

• Effectively reduce water consumption
• Reduce run-off into public sewer network
• Can be used on any site

Cons

• No financial incentive

These systems treat and store the water from showers and sinks and recycles it for toilet flushing and gardens. They need smaller tanks than RWH systems and so cost a little less at £2-3,000. They can also be integrated into a combined rainwater / greywater harvesting system.

One drawback is that you have to assume that there are no serious contaminants in the water which need more effective treatment, such as blood or urine. This may not be possible to guarantee, especially with babies or toddlers.

Like RWH systems, they only really make sense where access to water is limited or metered.

Heat pumps

Pros

• Can provide heat very efficiently
• Make a decent payback with the RHI

Cons

• Still rely on electricity
• Require well-insulated house to be effective

There are a number of types available, but they all fundamentally work in the same way. Electricity is used with a refrigerant which passes through metal coils, and it extracts heat from a material, and provides it to another. In the case of a fridge, it removes the heat from the small, insulated space of the fridge and moves it outside. An air conditioning unit is exactly the same but on a larger scale. Fundamentally they are a great idea because they allow us to create heat more efficiently.

Heat pumps are more effective if the coils pass through a material which is a better conductor of heat, and ideally warmer than air temperature. The ground is consistently warmer than the air, so this creates a better heat pump, and water is a better conductor, and has the ability to flow so the heat can be extracted from it more effectively. Because of the greater efficiency, a ground source heat pump will generate 3-4 times the heat the equivalent electricity would generate, and a water source heat pump is even better, generating 5-6 times the heat.

The operating temperature of a heat pump is generally quite low, heating water to around 30 degrees. A central heating system runs on water at around 80 degrees, so a conventional boiler would still need to do quite a lot of work on the pre-heated water to make it sufficient to heat a house. It is much more efficient if a heat pump can be combined with an underfloor heating system which runs on water at around 30 degrees, and so the boiler does not need to do nearly as much work.

The problem with heat pumps which means they are still allocated into the camp of Eco-Bling is that they still use electricity to generate the heat, which is less efficient than other methods of heat generation. Gas is generally double the price per kWh than Electricity, so an Air Source Heat Pump will not generally give any savings, and a Ground Source and Water Source are not as efficient as they first appear (i.e. 2-4 times better than gas). They can however, still be part of an effective energy saving strategy, as long as the fundamental issue of heat loss has been targeted first.

Air source heat pump (ASHP)

This is a simple, wall-mounted or floor-standing unit on the outside of a house, which looks a lot like an air-conditioning unit. These are the cheapest heat pump to install because of their simplicity, so costing £7-11,000, taking into account a fuel saving of £85/year and an RHI of around £1,200/year, they should achieve payback in 7 years, after which the government is paying you £100/month, which is nice!

Ground Source Heat pumps (GSHP)

It is generally a system of pipes which are laid in a series of loops like an underfloor heating system, under your garden. These are around a metre deep and a metre apart, and should be sized to make sure that the heat they extract from the ground is sufficient for the heating season, and is re-stocked by the sun during the summer. If space in the garden is at a premium, these can be laid vertically in boreholes, although this is a more expensive solution. They cost £13-20,000, and give a potential saving of £200/year compared to a modern gas combi boiler, which assuming a medium cost, to achieve payback in 82 years. So it’s still a big investment for relatively low savings. However, the RHI on these is quite favourable and when taking this into account, it would achieve payback in 4.5 years which is much more healthy.

Water source heat pump (WSHP)

These are a series of loops much like a ground source heat pump, but laid in water and weighted down to prevent them floating to the surface. Again, the system should be sized to make sure that the heat being extracted from the water is sufficient for the heating season, and it can be re-stocked by the sun during the summer. There are cases of water source heat pumps causing bodies of water to freeze solid because they extract so much heat from the water! The body of water therefore needs to be a lot larger than a pond, more like a lake, which does unfortunately mean that this technology is only useful on a minority of sites. They are still relatively specialist, so there is not enough cost and savings data on which to base predictions.

Geothermal energy

This is a variant on a heat pump, but rather than burying the pipes around a metre deep in your garden, they are put into a borehole which travels a lot deeper into the earth and so makes more efficient use of the earth’s heat. They are still quite specialist, and less popular than ground source heat pumps, the main reasons being that they are less accessible if something goes wrong and the pretty substantial outlay to start with.

Off-grid drainage

If you cannot or do not want to connect into the public sewer network, you can store the sewage from your house on site. The main choice is whether you go with a Septic Tank or a domestic Sewage Treatment System. The Septic tank is cheaper, but stores all the waste from the house for extraction at regular intervals by lorry. A Sewage Treatment System treats the effluent so the the liquid is allowed to run-off whilst the solids are stored for collection. Collections are less frequent (and so cheaper) with a Sewage Treatment System. However, in most sites it makes financial and hygienic sense to connect into the local sewer network.

Reed beds

Reed beds can be used to treat the effluent run-off from a house, but this will create a lot of unwanted smells. They also need to be at least 1-2.5 sqm per person which makes them quite large. Both of these reasons make them impractical for most urban gardens! They can be combined with a sewage treatment system which takes out the worst (and smelliest) of the noxious substances first.

Eco-Minimalism

So, having explained how each of these is not the main priority in terms of an Eco-House, I don’t want to make out that there is no point in trying to be Eco, or trying to be better for the environment, but what should you do to make your house into an Eco-House? The answer is to focus your money on the fabric: the insulation of the roof, walls and floor, achieving a high level of air tightness and designing all the details right so that heat loss is dramatically reduced. Installing a heat pump on a traditional house is like a fridge with a door which does not seal. It will never achieve the right temperature and it will take a lot more electricity than necessary. Once your house is as air-tight and well-insulated as that fridge, then the heat pump will start to work. So the focus has to be on the basics.

Skip onto my next section to see more

The main aim of Eco-Minimalism: Reduce heat loss

The post What is Eco-Bling and why isn’t it a priority? first appeared on Archi-HOUSE.

Eco-Minimalism

This is a concept which has only fairly recently made it onto the sustainability agenda. It is a reaction against the somewhat lecturing and moralistic version of sustainability which has been promoted for some time. It is against the complicated technological fix, and looks for the simpler underlying message.

As an Architect I am often involved in the specification and budgeting of people’s house renovations and extensions, and I find that they are torn between the amount of works they can do, the quality of materials they can use, and the increasing pressure to integrate sustainability or eco-measures into the building.

I naturally share a lot of people’s enthusiasm for sustainability. Who doesn’t want to be kind to their environment? But the way that it is rammed down people’s throats and people are guilt-tripped into putting some expensive technology on their roof which they need to spend years paying for, or at the cost of the house they really want, has to be misguided, however well-intended.  The way that it is presented with a religious-like fervour makes me uncomfortable, and you are made to feel like a doubting unbeliever if you question any of the current dogma!

I feel that more people could get on board with this agenda if it was more transparent, and if we were encouraged to do what we can rather than guilted into making a token gesture.

The rise of sustainability

Sustainability has been an increasingly important issue in architecture over the past 50 years. It started life as an alternative lifestyle for people who were disillusioned with the city and wanted to get back to nature. Over the years it has become more mainstream and being environmentally responsible has been acknowledged as the thing to do. It was a part of our culture as early as the 1970’s, when the TV show The Good Life portrayed it as an admirable all be it somewhat idealistic goal, but it has gradually increased in popularity. One key reason is that the rising cost of energy since then, which has made it more motivating, i.e. there is now a carrot as well as a stick.

The government has tried to encourage us down this route, again with a carrot and a stick, in the form of regulations (the stick) and subsidy (the carrot). The value of the carrot has been questionable, and as the value of the subsidies are steadily reduced to reduce government expenditure, they are getting less effective. The Green Deal has largely proved to be a failure because take-up was so low, but the government’s targets were wildly ambitious whilst funding was reduced, so it was never going to happen. The building regulations however, have gradually enforced ever greater insulation of properties, and as we need to comply to get permission to build anything, it has been very effective. Our new-build homes now lose 6 times less heat than traditionally-built houses.

There is a great deal of scepticism about sustainability in the construction industry. We were seeing lots of buildings in the architectural press which had great ideals of sustainability, but which failed to live up to the ideals. Huge energy savings were being promised, which never materialised and the investment never paid off. In the industry, we were also sceptical of the eco-aesthetic which was developing. Lots of glass, solar panels and wind turbines were cluttering up our houses, which look clumsy, and seemed to dictate a new architectural style of “Eco-Architecture”. While this is fine in some locations (particularly remote ones) in cities where you have neighbours, and especially in areas with a particular architectural character, slapping a load of solar panels on the roof looks incongruous. If Eco-Architecture is going to be mainstream, it needs to work in our cities.

The photo above is of a scheme in Beddington, South London which gained a lots of awards. It has great eco-credentials, but it also has a very obvious Eco-Aesthetic, which is not to everyone’s taste and really make it stand out in it’s surroundings. Whilst blending in is not always the right thing to do, coming along to a dinner party with a mohican, rings and tattoos is not really is not really going to win you many friends either.

I also found it frustrating when I read books about Eco-Architecture, because they tend to describe all the technologies available in a lot of detail, but with little information about why each should be installed, and which were not worthwhile. There was no objective advice on what was most suitable. In real life, every job has a limited budget and we need to be economic with the financial resources we have. Increasing the budget for sustainability reduces the budget for floor area, which is usually the priority, and even when the occasional project comes along with a  generous budget and sustainability high on the agenda it is still hard to know which is the best way to achieve the requirement. How far do you go? When do you stop? As sustainability is only ever part of the brief, with a lot of other requirements like as natural light, views, functional layouts and certain rooms competing for the budget, it often ended up losing out to the others.

Eco-bling

Eco-Bling has registered enough with the public consciousness to have been recently added to the Collins English dictionary as “Equipment that is energy-efficient but less effective than simpler technology”. Solar panels, wind turbines and green roofs give the appearance of being sustainable, but often under the surface they are not as green as they appear. So there is a healthy scepticism from the public as to what Eco really means, and other more derogatory terms are used like “Telly-tubby Architecture” referring to the popularity of green roofs in this sector and “Greenwash” which is doing something to appear green whilst covering up something else which is not green at all.

To deal with this negative stereotype, some people in the sustainability movement have tried to make it more transparent and accountable, and Eco-Minimalism is a move in this direction. It is a term coined in a book I read recently, which calls for this as opposed to Eco-Bling.

Howard Liddell of Gaia Architects, wrote a book called “Eco-Minimalism: The Antidote to Eco-Bling”, where he assigns all of the various environmental strategies into the camps of Eco-Bling or Eco-Minimalism. This practice is not some Eco-Sceptical practice, they are hard-core Eco-Warriors who have been designing buildings since the 80’s which would come into the category of “experimental”. They have been building Eco-Architecture in Scotland since 1984. Rather surprisingly, his approach is very common sense, which is refreshing to an otherwise sceptical Architect.

His very brief book describes some of the more hair-brained Eco buildings which were built whilst people were still experimenting with what worked and what didn’t, and outlines the basic lessons learned. The most popular strategies are Passivhaus (a German building standard which involves super-insulation, air-tightness and Mechanical Ventilation with Heat Recovery – MVHR), Solar panels (both Photo-voltaics – PV and Solar Thermal – Hot Water), Combined Heat and Power (CHP), Heat Pumps, District heating systems, Wind turbines, Green roofs, Reed beds, Recycling of Rain and Grey water (all water from inside the house except foul drainage), Passive solar energy, Biodiversity and Sustainable drainage.

Solar panels, CHP, District systems, Wind turbines, Green roofs, reed beds and water recycling are all described as Eco-Bling, whereas Passivhaus, Passive solar energy, Biodiversity and Sustainable drainage are described as Eco-Minimalism. The thing which is common between the Eco-Minimalst strategies is that they are simple and passive, not requiring a lot of ongoing maintenance, and reducing performance over their service life. Eco-Minimalism is an integral part of a building. It does not require a particular design style, and so can be applied to any building.

Clean, Lean and Green

Planning authorities have picked up on the fact that sustainability is a murky world of broken promises, and although Sustainability statements were required as part of a lot of large planning applications, a lot of these were very woolly. So after looking into the efficacy of the different sustainability strategies, they came up with a sustainability hierarchy which they termed Lean, Clean and Green (listed in order of priority).

Lean involves using less energy, Clean involves distributing that energy cleanly, and Green involves using renewable energy sources. Lean (i.e. less) energy consumption involves the basics, and so includes insulating to a high standard, achieving a high level of air tightness and eliminating thermal bridging, as well as reducing electricity consumption by using low power appliances and lights. Clean involves avoiding the inefficiency of the power distribution network by producing power locally, (i.e. CHP – Combined Heat and Power) but this is usually provided on a neighbourhood scale so it is not applicable to an individual home. Green involves renewable energy, and includes solar panels, wind turbines etc. So after their own research, they found that passive strategies were far more preferable to active ones.

This kind of hierarchy sets out what the priorities are in terms of sustainability, and so we can look at buildings and consider whether their green credentials live up to the promise. The impressive Strada tower in London (opposite) might be an unfair example, but it wears it’s Eco-credentials on it’s sleeve. The huge wind turbines on the roof provide up to 8% of the electricity usage for the building. However, if we look at the priorities for a building, we can see that insulation and air-tightness (i.e. reducing energy consumption rather than providing renewable sources for that energy) should really have been exhausted first before resorting to the wind turbines. And is the building super-insulated and air-tight? No. So it means that the wind turbines are essentially a huge piece of Eco-Bling. It is still noble to have made an attempt to be more green, but the way that it is done needs to be more rational.

What makes an Eco-House?

So how should we build our new Eco-houses? It is clear that we need to focus on the basics. It involves getting the heat loss right down, as close as possible to zero. It then involves adding MVHR to ventilate your extremely air-tight and insulated homes in an efficient way. We can add technologies on to get electricity or water heating from a renewable source, but this should only be an extra once the basics have been put in place.

Eco-Minimalism is about making Eco-Houses which are not visible from the outside, which still meet the needs of modern life, but use dramatically less energy to do so. Any terraced house, flat or semi in the country can be an Eco-House. But the only way of telling this is from the heating bills. The sustainability is built into the building, and as a part of the building it will last as long as the building. And as it is passive, it continues to function throughout the life of the building with little to no maintenance.

Eco-houses certainly should not have a “look”, and you will not know them by their solar panels, but they are super-efficient down to their bones. An Eco-house is a polite neighbour and you might not even know that it was an Eco-house at all. In this photo one of these terraced houses is a near zero energy Passivhaus retrofit project, but which one? It’s impossible to tell from the outside, because it’s only an Eco-House on the inside, in the guts and the bones. On the outside it’s just a normal house on a normal street. The only way you could tell is if you could see the heating bills!

The post Eco-Minimalism and Eco-Bling: An introduction first appeared on Archi-HOUSE.

What’s the best way to insulate your house?

We have established that the most important thing is to insulate your house, but where do you start?

It can help to think strategically about which parts of the building to insulate first. The walls are the biggest source of heat loss, followed by the roof, then the floor, and then windows. Windows therefore are much less of a priority than the walls, roof and floor, and given that double glazing is comparatively expensive it is not usually the most economic solution. However, it is one of the simplest. In a lot of old buildings, the walls are solid with no cavity, so they need to be insulated externally or internally, which changes the look of the building or has a serious impact on the use of the building.

So what is the most economic solution for each building type?

All houses

Roof insulation

Roofs can be insulated easily, and the construction has not changed a lot at all over the last 100 years. The way that roofs are built has changed, moving from large structural timbers and purlins to trusses, but fundamentally the layer which is being insulated is still the ceiling joists, whichever era it was built in, they are always insulated in the same way. 150mm thick mineral wool laid between the joists will get a reasonable U-Value of 0.25 W/m2K and laying another 150mm of mineral wool the other way over the timber will get a much healthier U-value of 0.16 W/m2K. If you still want to use the attic space for storage, clever plastic spacers have been designed which you can lay a chipboard floor deck over.

Double / triple glazed windows

A good set of double glazed windows will achieve a U-value of 1.2 to 1.6, which is much better than the 5.0 that a single glazed window will achieve. Triple glazing will get 1.0 to 0.6, which is a significant improvement again, although you can see that you will never get a uvalue like you can in a wall. The next generation is now quadruple glazing which achieves U-values of 0.35 which is staggering and is actually close to being as good as a wall, but the cost is equally staggering.

Another benefit of double glazing is that the windows will be sealed in properly with mastic and epdm seals which prevent draughts, and this can reduce heat loss as much as the insulation of the glass. Other benefits of double glazing is at they prevent condensation on the inside face of the glass, because the two faces are separated and a cold external surface doesn’t come into contact with the warm internal air. They also reduce sound transfer significantly, which can further improve internal comfort. 

Traditionally-built homes (Pre 1920)

Solid masonry walls are more complex, and the only solution is Internal or External insulation. In both locations the same materials would be used, i.e. a rigid board in the form of Phenolic, PIR or EPS. While mineral wool can be used internally, they use more space for the same U-value, and if you refer to my Which Insulation page, you can see that PIR works out at a similar cost for the same U-Value, so as you also get the added benefit of space saving, it is an economic solution. Phenolic insulation is the Rools Royce of insulation, but it is a lot more expensive, so it rarely works out as economical. The uvalue of a solid wall will work out at around 3.0. The heat loss from this is similar to a window, so adding insulation has a dramatic effect. 100mm of mineral wool will bring it down to 0.36 and 50mm of PIR will achieve a similar value of 0.35. Given the surface area of the walls, this is often the most significant way to reduce heat loss, and so should be well worth the investment.

Internal wall insulation

This can be done for £8-10,000 so is a significant expense, but it will have a more significant impact on heat loss than insulating floors, roofs or double glazing.

If the walls of your house are true then you can fix the insulation boards directly to the external wall and plaster the internal face. If you can’t rely on this to give you a smooth internal finish timber or metal lining will take out the discrepancies in the wall surface. All the boards should be butt-jointed as closely as possible, and taped at the junctions.

You need to be careful to avoid potential issues of condensation forming between the insulation and the existing wall. It is important that the moisture in the air is not allowed to get through into the insulation where it can cause damage, so the aim is to create an air-tight layer on the inside face of the insulation. This is done by laying a VCL over the insulation board which is taped and sealed at all junctions, or if you have used a foil-backed insulation, the joints in this can be taped to give a seal which is air-tight enough for this purpose. This is not an ideal junction as you are taping the plaster rather than the foil face inside, which does not form a properly air-tight seal, but the amount of moisture getting through these gaps is minor and not going to have any impact on your walls. However, a separate, fully taped VCL is the ideal solution as it will prevent the movement of any moisture into the wall.

External wall insulation

Mineral wool, EPS, PIR or Phenolic insulation can all be used in this situation. Mineral wool in the form of batts (semi-rigid boards) are used, but are less preferable to the more rigid boards, as they are much more robust and resistant to water penetration.

The boards are fixed walls or with an adhesive to the wall behind. A metal (or sometimes fibreglass) lathe is then applied to the insulation which gives something for the render to grip on to. The render will be an acrylic render as these have some flexibility. A cementitious render is a definite no-no as it will crack with any movement of the insulation board below. Not that the insulation will move, but there will be natural expansion and contraction in the board which needs some tolerance to be designed in. If you are planning to clad your building in timber or tile rather than a render, you will need to lay a breather membrane on the insulation, and then fix timber battens through the insulation to the wall behind to give a secure fixing which will carry the additional weight of the timber / tiles  or even brick / stone slips. These create a ventilated cavity to the rear of the cladding, which allows the back of the cladding to dry as well as the front, which means that it is not damaged in the long term by by repeated wetting and drying.

The method of fixing depends on the pull-out strength required, so if you are going to render the board externally, you will need to mechanically fix the insulation, but if you are applying a cladding system such as timber cladding or hanging tiles which connect back to the substrate wall, the insulation can be adhesive-bonded. You want to minimise the number of fixings going through to the brick, because even though they are thermally broken, they still form a thermal bridge.

There are a couple of tricky details for external wall insulation, because your house was designed with the wall thickness it currently has, and some of the external features may be affected. Windows and doors will often need a new aluminium extension sill to take the water away from the surface of the building. The eaves may also need to be extended so that they continue to project beyond the edge of the walls.

Ground-bearing slabs

These are tricky and expensive to insulate because you need to raise the level of the internal floors, and so not for the faint of heart. You will need to install a floating floor, I.e. a layer of insulation over the slab with a chipboard deck over the top to prevent the insulation flexing. Most rigid boards can be used in this way, and the choice often comes down to uvalues you are planning to achieve. The definition of a floating floor is that there are no fixings into the slab. The self weight of the floor prevents it from moving about and the tongue and groove in the chipboard creates a joint which prevents movement pretty well.

The installation of the deck is straight forward, but the difficult bit is how it affects everything else. The floor level in your house will change. This affects the steps at the front and back door, the external doors, all the internal doors and the stairs. The doors can be cut although this can affect the appearance especially if they are panelled doors. Even more difficult is the stairs. You don’t want to have a small riser on the first step, and the building regulations require that they are all uniform, because otherwise this is a pretty major trip hazard! To make them uniform, you would need to add packers onto every step to bring it back to a uniform height. This would be a real pain for your joiner, using lots of thin bits of wood, by there’s no reason it couldn’t be done. Alternatively raise the floor level by the height of one riser so that the stair has one less step, but this would affect the ceiling heights significantly as the riser will be around 200mm / 8 inches. As I was saying, not for the faint of heart!

Early 20th Century houses (1920-1970)

Cavity wall insulation

The walls are usually cavity walls, and they are the most straight forward. The cost is very low, around £300-600 depending on the size of the house, and so should be done wherever possible. Filling a 100mm cavity would achieve around 0.35 W/m2K or 0.29 with a high performing EPS bead (grey). This is a specialist job, but installers have found solutions to the most commonly found problems. There used to be issues with blown mineral wool settling in cavities or becoming waterlogged and rotting within the cavity, so it was found that mineral wool was not really a suitable material, so this has been changed to EPS (Extruded Polystyrene) beads. These are non-deleterious (they do not rot). Their performance is not affected by water, and they do not encourage the transfer of water across the cavity because they are water repellent. Another issue which did come up was that the beads all came flooding out of the cavity if a hole was made a few years later, such as for an extractor fan. But this has been overcome by adding a bonding agent as the beads are pumped into the cavity so that they stick together and will not come out of the cavity in the future. There is also the issue of blown insulation in a terraced house, but this has been overcome by running a wire brush through the cavity along the line of the party wall to stop the insulation passing between houses.

Suspended timber floors

Floors are generally timber, which is also very simple to insulate. If there is access to the crawl space and it is large enough to get in to, it can all be done from below which is the most economic. The only costs are buying the insulation and a fabric netting (to hold the insulation in place) and a staple gun to fix it in place, which will cost a couple of hundred pounds at most. This is a job that you can do yourself as long as you wear gloves and goggles and pay care when cutting the wool slabs, because pushing them up from below is a messy job. The mesh is laid across the underside of the joists and stapled into the joists to hold the insulation in place. It can also be done from above, but this involves lifting the floor boards, which is a time consuming and fiddly job, especially if you want to leave the boards exposed which would leave any damage done to the boards while pulling them up permanently visible.

One interesting alternative to mineral wool is blown cellulose insulation. I cam across this on a recent project because the owner was keen to insulate without pulling up all the floor boards, because they were planning to sand them down and leave them exposed. Pulling them all up would have been very time consuming and damaged the floor boards so that they didn’t look good when laid back. They also couldn’t access it from below, because it was a flat and they were an intermediate floor. A flexible pipe is run through the space between the floor joists, and it only needs to access from one or two points, so we only needed to raise a few floor boards. This system also allows it to be done from below. A few holes are cored in the plasterboard to allow the pipe to get in, and the insulation is pumped in, and then the hole is filled and plastered over to make good. This is also bit of a wonder Eco-product because it is made from recycled newspaper. Recycling a product which was going to be thrown away, and is in itself wood, ticks a lot of Eco boxes.

Modern Houses (1970 onwards)

Insulated cavity

Most modern buildings have an insulated cavity, and so perform fairly well in comparison to solid walls. The floors and roof are also well insulated so there is less need to insulate and the returns on the investment are much less. If you are aiming for a very well insulated eco-house then there is always more you can do, but the basics are sound.

Timber kit buildings generally have mineral wool in the cavity, which makes them naturally quite well performing, achieving 0.26 with 140 mm of mineral wool within the studs.

Brick and block walls with a 100mm cavity and 50mm of celotex in the cavity achieve a very similar 0.27 or 0.28, depending on whether the insulation is foil backed or not.

This can always be improved with internal or external insulation to improve the uvalue and prevent thermal bridging, but the reductions in heat loss are less dramatic and the hassle and nuisance is less worthwhile.

The post A guide to insulating your home first appeared on Archi-HOUSE.

• Do they have examples of previous projects which are similar to yours.
• So they have experience in the specific type of architecture you are looking for?
• Do they have any initial ideas?
• Is the project achievable on the budget?
• Who will actually be working on the project? I.e. will it be the person you are meeting or someone else?
• Are they willing to provide statutory approval drawings only and not the full package?

The post Hiring an Architect: What you need to know first appeared on Archi-HOUSE.

Base load

The energy that is needed constantly for the running of your house.

Breather membrane

This is a water-resistant barrier which sheds the water off the building, and prevents it passing through into the timber kit behind. A typical timber kit building clad in brick will have this on the outer face of the timber kit. Whilst preventing water passing through it, it allows moisture in the form of water vapour in air to pass through it (hence the term breather membrane).

This ensures that if the timber gets damp, it can pass back out through the membrane over time. This is not needed in block-work construction because the block can tolerate an element of moisture penetration as long as it is allowed to dry out over time. An air-tight membrane should not be sued in this location because it would lead to moisture build-up in the timber kit, and potentially rotting the structure. There are many alternatives available, but the one manufactured by Tyvek is Supro.

Snagging tip #1: This does not need to be sealed, but ensure that all upper sheets overlap lower sheets to shed water.

Build tight, Insulate right

A strategy for making sustainable buildings which focusses on reducing air leakage from buildings to a high level, and then providing mechanical ventilation to ensure that the indoor air quality is maintained at a high standard. This will often be a part of a fabric first strategy.

Damp proof course (DPC)

This is at the base of your walls which prevents the moisture from the ground rising up through the masonry of the building. It is usually a sheet of black plastic, located 150mm above ground level to prevent water which splashes off the ground from bypassing the DPC. In traditional buildings without a DPC, the mortar can be injected with a water repellent compound, but this will need replacing over time.

Damp proof membrane (DPM)

This is underneath your floor slab and prevents moisture rising up through the slab, and is generally a sheet of plastic.

Snagging tip #1: Make sure it is laid on a sand blinding to prevent it being damaged by the hardcore below.

Snagging tip #2: Make sure it is lapped with the DPC so that moisture cannot bypass the DPM and DPC to get into the slab.

External envelope

All the external parts of the building which meed to be insulated to prevent heat loss, i.e. the walls, floors and roof.

Fabric First

A strategy for making sustainable buildings which focusses on the “fabric” or the “external envelope” of a building rather than on renewable energy sources like solar panels or the like. This involves insulation, air-tightness and reducing thermal bridging.

Floating floor

This is essentially a floor which does not need to be nailed or glued to the floor below. It most often refers to a floor laid on timber battens or on a solid sheet of insulation. These are usually used for insulation, either as acoustic isolation to prevent the transfer of sound through solid elements like nails, or for thermal isolation by preventing heat transferring through solid elements like a timber floor structure.

Hygroscopic

The ability of a material to absorbs moisture. The desiccant included in a lot of packaging for electronics is hygroscopic, i.e. it absorbs moisture in the air to protect the product. This is also packed into the metal strip around the edge of a double-glazed window to absorb any moisture and prevent condensation. A non-hygroscopic material would be used in insulation beneath a concrete slab where it is going to be located beneath the DPM, and so needs to not be affected by water. EPS products are often used in this situation, such Kingspan Styrozone.

Mechanical Ventilation with Heat Recovery (MVHR)

A whole-house ventilation system which extracts air from the Kitchen and Bathrooms and supplies it to the Living and Bedrooms. The two air paths are passed very close to each other so that up to 95% of the heat is transferred from the outgoing to the incoming air.

Peak load

The maximum energy consumption of your house, e.g. when everyone is having a shower and making coffee for breakfast.

Raised floor

This is usually used to allow services like electrics or plumbing to be run through a space without affecting the acoustic or thermal insulation of the floor, or just to bring a floor up to a certain level, i.e. so that it ties in with another floor level etc.

SAP Calculations

SAP Calculations (Standard Assessment Procedures) are required for all new-build houses in Scotland and England. It quantifies the likely energy use per unit of floor area and CO2 emissions, and can be used to estimate annual heating costs. It is based on standardised assumptions for occupancy and behaviour, so cannot be relied on to be 100% accurate, but it is very useful to give a way to do a like-for-like comparison with other houses.

Every few years the government makes the SAP gradually more and more onerous to achieve. To achieve a pass for a new-build house requires that all the above are carefully considered, with U-values around 0.21 for walls, 0.11 for roofs and 0.16 for floors, as well as a good air-tightness level (around 5) as well as careful detailing of all thermal bridging. Any unusual details if you use non-standard forms of construction will probably need to have specialist Psi-value calculations to be carried out to ensure that heat loss has been adequately prevented.

Slapping

Knocking a hole through a wall to form an opening for a window or door. Why on earth it is called this, I don’t know!

Snotter

Lumps of mortar which drop into the cavity while laying a brick wall and sit on the wall ties. These breach the cavity and allow moisture to pass through the two leafs, so should be avoided as much as possible. If the brickwork has been done badly and there are a not of snotters, you can ask the Contractor to run chains through the cavity to remove them.

Thermal conductivity

The ability of heat to pass through a material. This is the K-value of a material, which is measured in W/mK and is called the “lambda” value of a material. This is useful because it allows us to compare the insulation properties of different materials. This can be combined with the thickness of the material to give you another value (R-value) which can be added to each other. Once all the R-values have been added, the inverse of this is the U-value. Not that you need to know all that, you just need to know that it allows you to compare the insulation properties of materials.

Steel: 50

Wood: 0.12

Mineral wool: 0.04 (Rockwool or Isover)

Blown cellulose: 0.035 (recycled newspaper)

EPS: 0.03-0.038 (normal polystyrene)

XPS: 0.029-0.039 (denser cell structured polystyrene)

Polyurethane: 0.022-0.028 (PUR is interchangable with PIR)

Polyisocyanurate: 0.022-0.028 (PIR – Celotex)

Phenolic foam: 0.021-0.024 (Kingspan)

Thermal mass

The ability of a material to retain heat, and therefore the time taken to heat up and cool down, i.e. concrete and blockwork have a high thermal mass and timber kit is low.

Parge coat

A cement layer on the inside of a blockwork wall which is not vapour permeable. This is often used in masonry construction to create an airtight barrier, to replace the VCL in a timber kit construction.

SAP calculation

The calculation which is required to show the heat loss for a building. It takes into account the insulation of all parts of the external envelope, the thermal bridging, air tightness, type of heating system, extent of glazed openings as well as a lot of other factors. The standard required to achieve a pass goes up each year. This is usually done by a suitably qualified SAP assessor rather than your architect or other consultants.

Solar gain

Energy gained from the sun, seen when the room gets hot on a sunny day even though it may be cold outside. South-facing windows gain more energy from the sun each year than they lose in heat loss.

Thermal bridge / cold bridge

A gap in the insulation envelope, where heat can pass out of the building without going through insulation, e.g. at windows where the reveals are not insulated, or where timber posts occur in timber frame.

Thermal mass

The ability of a material to absorb (and then release heat). E.g. a concrete slab has a high thermal mass because it takes a long time to heat up, but once warm it radiates it’s heat for a long time and takes a long time to cool down as well. A timber frame wall has a low thermal mass and so whilst it warms up quickly it also cools down more quickly. Neither property is required for an eco-house to function, but it’s impact on the rest of the system should be understood.

U-value

The ability of a form of construction to resist the passage of heat. The units are w/m2k and take account all of the materials and their thicknesses, and the lower the better. A typical insulated cavity wall may achieve 0.25 whereas a Passivhaus wall would achieve 0.10 and an un-insulated wall around 3.0.

Vapour control layer (VCL)

As the name suggests, it controls vapour within the wall. This prevents moisture passing through into the depth of your wall, from the inside. It is already protected from the outside by the breather membrane. Moisture from your house can enter the wall construction in the form of water vapour in warm, humid air, but then as it cools down in the wall construction, the water retaining capacity of the air reduces and so it condenses in the material, i.e. within the wall. This is not a good thing in timber kit construction because if it remains in the timber kit for any length of time it can damage the timbers.

This is prevented by installing a continuous, non-vapour permeable membrane, i.e. a VCL, across the inside face of your wall. These are not needed in masonry construction because they are more tolerant of some moisture ingress which will dry out over time without damaging the wall.

A vapour control layer can also be referred to as an air-tight layer, because as well as preventing moisture from passing through, it generally prevents any air from passing through at all, which allows it to also function as the air-tightness layer.

These are made by many different manufacturers and each looks different, and their appearance varied from basic plastic sheeting to a coloured or silver finish. The silver types give an enhanced u-value because they reflect the heat ack into the building. Tyvek manufacture several, including Airguard: Control (Standard) and Airguard:Reflective (Silver).

The silver foil finish on a lot of rigid insulation boards like Celotex also acts as a VCL and taping the joints with a foil tape avoid the need for a separate VCL.

Snagging tip # 1: Make sure that all joints between sheets and with windows and doors are taped.

Vapour permeability

The ability of water vapour to pass through a material. This is measured in a variety of  ways, the G-value (MSs/g) takes into account thickness.

Sheet of plasterboard: 0.24

Breather membrane: 0.5

OSB: 3.6

Brickwork / Timber: 5

Vapour control layer: 1,000

Glass: 100,000

Foil-backed plasterboard: 100,000

The post A bluffer’s guide to Architectural terminology first appeared on Archi-HOUSE.

Glass wool roll

Glass wool is made from a spun molten glass and sand mixture and is very flexible and because it is also cheap, it is used in a lot of places. The best places to use it are where space is not an issue, so within joists in an attic or below suspended timber floors. It has a Lambda (K) value of 0.04 to 0.032 depending on the product specified. This can be used in the form of a roll or a semi-rigid sheet (also called a batt). It can also be loose fill if it is blown into a cavity (although this is becoming less popular because the polystyrene beads are more resistant to compression and moisture ingress). It is also wrapped in plastic and formed into tubes to create fire barriers around windows and doors and within walls. Popular brand names are Isover by Saint Gobain and Earthwool by Knauf, as well as similar products by Superglass and URSA.

Mineral wool roll

Rock wool is similar to glass wool (and often called mineral wool) but be aware that these are often confused. It is formed from molten basalt rock, and is denser than glass wool so gives better acoustic performance, has better fire performance and moisture resistance. It performs the same as glass wool, with a Lambda (K) value of 0.035, but is around double the price of glass wool. It can also be used in the form of a roll or a semi-rigid sheet (also called a batt). Popular products include Knauf’s Earthwool and Rockwool.

Sheep’s wool roll

A product that often catches people’s imagination is sheep’s wool. This is a similar insulator to rock and glass wool, with a K-value of 0.035 to 0.04 W/mK, but it is a completely natural material, without the need for energy intensive manufacturing processes like melting glass or wool! The only factory processes are cleaning and adding a pest and rodent prevention treatment. Unfortunately it is in limited supply as you have to wait for it to grow, and so it is more expensive than the other wool products, and can cost 3 to 6 times the amount of artificial wool depending on the performance. One big bonus is that it is not an irritant to skin or eyes, and so goggles and gloves do not need to be work when it is being used.

Loose polystyrene beads

Existing cavity walls should be insulated with blown beads of polystyrene (EPS). This performs similarly to mineral wool with a Lambda (K) value of 0.040, and is more suitable for cavities as mineral wool can slump under weight and be damaged by water ingress. A binding agent is often added as it is blown into the cavity to ensure that they stick together when they dry, so that there is no risk of them all flooding out when you next install an extractor fan! These are generally white in colour, although grey ones are also available which have graphite added to improve the Lambda (K) value to 0.033.

Loose cellulose

Or recycled newspaper, is a fairly recent introduction to the insulation market. It performs similarly to mineral wool in terms of heat loss, with a slightly better Lambda (K) value of 0.035 W/mK, and as recycled newspaper it is a waste product rather than a new (and oil-based) product, which gives it excellent environmental credentials. One issue is that because the product is not yet established, there is not the same amount of test data and technical support than for the more commonly specified materials, but this is definitely one to watch. It has flame and damp retardant ingredients added to the product during processing so that it does not create a fire risk, and is not subject to rotting if it gets damp. The flame retardancy is effective enough to allow you to hold a handful of it and apply a blow torch without it or your hand burning! The main manufacturer in the UK is Thermofloc which replaces Warmcel which closed last year. Although it is no longer made in the UK, the price has gone down significantly since it has been imported from Eastern Europe. As it is still an unusual choice you have to shop around to purchase it and may well need to factor in a delivery cost for it as it is not readily available at trade merchants.

Expanded polystyrene board

Polystyrene is also available as a board. In this form it is most commonly used below a slab because as a board it will not be damaged by the weight of the building above, and it is a lot cheaper than the other better performing insulation boards. However, as the more expensive boards are thinner they can reduce the amount of excavation needed, and so still give a saving so this should be assessed for every project. It is also highly water repellent, allowing it to be used below the DPC whilst retaining it’s insulation properties. It is worth noting that this should be protected from a naked flame, as it is flammable. It achieves a Lambda (K) value of 0.035, or it is available in a grey form with graphite added it achieves 0.032. Manufacturers include Jablite, Arbet, Kay-Metzler & Styropor.

Extruded polystyrene board

This process of manufacturing polystyrene insulation improves the thermal properties of the board, allowing it to achieve a Lambda (K) value of 0.029 W/mK. This board is often coloured rather than white to distinguish it from expanded polystyrene, and it has a denser cell structure which is visible if you look at the two products together. Popular brand names include Kingspan Styrozone, Knauf Polyfoam, Styrodur by BASF, as well as products from Celecta, Sundolit and Marmox. This is generally only used on large projects for underfloor insulation, so it is not available in most trade merchants.

Polyisocyanurate board

PIR is a rigid board material and the sheets often have a foil facing to one or both sides. It has very good insulation properties, with a Lambda (K) value of 0.022 W/mK. Celotex is the main manufacturer in the UK, and all their boards are made from this. It is very similar in chemical make-up to Polyurethane insulation, although the proportions of ingredients are altered. Other manufacturers include Recticel, Ecotherm & Xtratherm.

Phenolic board

Phenolic insulation is a rigid board material and the sheets often have a foil facing to one or both sides. It has the best insulation properties, with a Lambda (K) value of 0.020 W/mK. Kingspan is the main manufacturer in the UK, and most of their boards use this. These are more expensive than PIR and they perform slightly better which gives a marginal decrease in the wall thickness needed to achieve the same U-value, but as the performance increase is marginal, most Contractors find that PIR is the most economic solution. At the moment, Kingspan is the main manufacturer in the UK.

Polyurethane foam

This is a plastic foam formed by combining two materials which react to create the foam. It is commonly used on site in a spray form which allows it to be applied to cavity walls during construction. It achieves a Lambda (K) value of 0.023 which makes it a very good insulator. However it is not a very popular form of insulation because of the mess created and the fairly specialist nature of the installation. It also has an impact on the programme of a project because the cavity walls need to be ready for spraying in a single installation by specialists, whereas mineral wool or rigid boards can be installed by any tradesman and can be done on a piecemeal basis. This is popular in American and Canada, but as yet has not taken off in the UK, and so is not widely available.

Multi-foil sheets

This is a fairly modern invention which is made of several layers of reflective foil, sometimes with thin insulation layers between. U-values can always be improved by the addition of foil layers to the inside and outside, so the logical extension of this is to have a material made up entirely of reflective layers, which is a fairly idea, but Lambda (K) values do not apply to this material, as the material is not an insulator in itself, and actually plastic and metal sheets are poor insulators, but they work by reflecting the heat. The theoretical U-values which are possible are 0.19 W/mK for just 25mm of the material, but this has failed to perform up to it’s promise in the industry standard “hot box” test and when tested as part of an overall roof construction it was found to achieve 0.8 W/mK, which is actually the same as what you would get from the same thickness of Rockwool! These poor test results mean that this insulation is not generally accepted by building control departments, so you would need to achieve the minimum requirement with standard insulation products and add this as an additional layer, although given the cost, I am not sure why anyone would.

Which type of insulation is the cheapest?

This is the million dollar question, which is hard to answer because they all perform differently for the same thickness, but I have done a quick study of some of the insulation materials available on the internet and weighted them all in terms of performance. The R-Value is a measure of the insulation offered by a material at a given thickness, so it allows us to compare materials. The R-Value is the thickness in metres divided by the K-Value, i.e. 100mm of Phenolic board is 5.0 as 0.1/0.2 = 0.5. Then we can work out the cost / R-Value by dividing the cost per square metre @ 100mm thick by the R-Value of 100mm of the material. XPS, loose EPS and Polyurethane foam are not included as they are not readily available from trade stockists, and need specialist installation.

Acoustic insulation

Sound transmission through a floor is a combination of airborne and impact sound which need to be insulated in different ways. Impact sound travels through solid elements so can only be prevented by isolating elements from each other. Floors in houses do not need to perform very well, so insulation is laid between the floors and specialist fixings called resilient bars fix the plasterboard ceiling to the floor joists. This gets an insulation value of 43db. A typical floor for a flat will protect against both with a floating floor made of timber board on a timber batten with a rubber back in as well as a plasterboard sheet between, and then flexible resilient bars are used to fix the plasterboard to the underside of the floor joists which gives a very good insulation value of 56db rw.

Whilst the rigid boards are not effective at providing insulation, wool rolls and cellulose are. Mineral wool is often used in a floor build up to increase the basic insulation of a floor from 36 to 40dB. Cellulose is denser and as a result should perform better. It is not yet widely used so does not have test data, but when used in walls it performed better than mineral or glass wool.

The post 10 most popular insulation materials first appeared on Archi-HOUSE.