Air Permeability Testing saving up to 20% of the UKs CO2 emissions and costs from heating homes.
Ever since witnessing my first Air Tightness Test (or more accurately an Air Permeability Test) on a new build house, I have been intrigued at the potential benefits of doing this on ‘old’ existing housing. I always wondered what the benefit would be.
As both governments and citizens of the world look to mitigate the impact of the climate crisis we find ourselves in, the race is on to find cheap, easy and effective methods of reducing our dependency on burning things. These effective methods that we need also ideally need to have a small carbon footprint, so that we’re not further contributing to the problem that we’re trying to solve.
This is where I think that carrying out Air Tests in existing homes needs to become a ‘thing’. Currently it seems to be either a very niche subject and inconvenience within the new-build sector of construction or in the even more niche sector of the ‘Grand Designs Passivhaus enthusiast’. From my experience in the new-build sector its seen as another annoying box to tick that very few trades people who actually build the houses ever get to see or understand, yet it is fundamental to keeping a house warm and comfortable and being able to keep energy consumption and bills under control, especially in the most extreme cold and windy days when it is most important.
What Actually IS an Air Test?
An Air Test or Air Permeability test is something that is done to find out how leaky a house is. The leakier the house, the more heat is lost by the precious warm air simply leaking through hidden gaps into the atmosphere and being replaced by unwanted cold air that is drawn in its place. The more it leaks the more it costs to run for the occupier, the more energy is used and thereby more CO2 is emitted in the process.
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The process involves fitting a big fan to the door of the property, temporarily sealing up any intentional ventilation, such as extractor fans and trickle vents, after which the fan is switched on and air is sucked out of the property and the air pressure both inside and outside is measured. This allows the amount of unintentional and uncontrolled ventilation can be calculated. A score is given which is carefully calculated from this along with other information about the property. When Air Permeability testing became a requirement on new-build housing in 2006 the minimum standard was to score 10 or less, which has now been moved to a score of 5 or less for every new build to comply with building regulations. A score of 3 or less is considered quite air tight, can be quite hard to achieve and would require manual ventilation to make sure that there is enough adequate ventilation for a healthy environment inside the house for the occupier.
How much difference does it make?
To find this out we decided to do a small sample of tests. We tested 3 properties and the results were as follows:
Recent 2006 newbuild mid terrace: First test 14.6 Second Test 10.0
1960s built detached bungalow : First test 9.9 Second Test 4.9
1920s built mid terrace pit house: First test 12.4 Second Test 6.8
It’s thought that the difference between a score of 15 and 5 makes around 15-20% difference to the amount of energy used and money spent on heating homes. This means that with an average of around £900 per year in heating costs, up to £180 per year can be saved, so with the cost of an Air Test being around £180, it would have paid for itself in as little as 1 years (even less time if you have a big leaky house!) and then go on to save ££s every year afterwards. Where else can you invest £180 and make this much per year in savings? As well as it being a financially sound idea, it often makes the living space more comfortable, less draughty and quieter as noise from outside is kept out. It also can reduce the work needed by air purifiers. Interestingly we have also found that houses with fires are particularly bad because a lot of warm air gets drawn up the chimney! - Another reason to block up and stop using fires.
On top of all this and the most important one for me is the environmental benefit. Saving up to 20% of the CO2 emissions from all the housing stock in the UK would be amazing. It also helps raise awareness of the importance of energy efficiency for people as well as helping to pave the way for future heat pump technologies and saying goodbye to the gas boiler once and for all.
If you would like to do an Air Permeability test on your own home (or friend or relatives! - please spread the word) if you have a draughty house (or are just curious and environmentally conscious) then please visit this website https://www.bcta.group/attma/members/air-tightness-testers/united-kingdom/ to find your local testing company, share this blog with them and tell them you would like to do an air test on a non new-build house so that they know what to expect. Also have a look at How To Do An Air Permeability Test page where you can find out what you need to do to prepare for and make the most out of doing an air test as well as a checklist.
Have a good check high and low, inside and outside and in every room and cupboard of your property and look out for gaps, cracks, holes, particularly around where skirting boards meet floors, around pipes, cables and windows and doors. Its good to be familiar with the house, and although you might live in the house, its often surprising what you find and see when you have a thorough root around!
If you happen to have dimensioned plans of your home, it is helpful for the air testing person to have these as it will save them having to measure up your house to put the data into the air testing computer, as they have to enter the dimensions of the home to calculate the results.
Once you’re familiarised yourself with where you think the air might be leaking out, its best to move any obstacles that might get in the way when carrying out the air test, often cylinder cupboards, under kitchen sinks, vanity units or easily removable bath panels and kitchen plinths can be cleared out to allow easier access to these areas so that you can seal up holes quickly and easily. You don’t want to have to start moving too many things while the air test is taking place. Also take note of any air brick vents, window trickle vents, extract fans, cooker hoods and any other form of intentional ventilation. The air testing people will need to cover these up for the test so they get an accurate result. Usually some masking tape does the trick. (Remember it is very important to uncover them afterwards, they are there for a reason!)
If you’ve done the above you should also try and get hold of some of the following to have on hand so that you can seal up the leaks while the air tester is there so you can do a before and after test if you wish to see how much difference you can make.:
Mastic/caulk/acrylic or silicone sealants and a sealant gun (a good idea to ask merchants or friends if they have any you can use up that might be going out of date soon that you can get cheap!)
Expanding foam
Adhesive strip seals
Masking tape
The Actual Test!
When it comes down to doing the test, if you’re contributing to the research, you will want to do a before and after test, so the plan is, once the intentional ventilation is sealed carry out an initial test to get a reading, say for example you achieve a reading of 13.2, then close all the internal doors and set the air test fan running again and open the door to each room one at a time just a little so that the door is ajar. If you put your hand near the gap in the door way you will be able to tell how much air is coming in from that room, and therefore which room is the most leaky and which one needs the most attention! Once you’re in the room, a tip is to have a damp cloth to dampen your hands as this makes it much easier to feel where the cold air is rushing in. Once you’ve located the culprit, simply chose the most appropriate sealant for the job and swiftly move onto the next one, until you’re happy that you’ve done your best to seal up everywhere. Then its time for a re test to see what your final result is!
One important thing to note, if you have a chimney, this can be temporarily sealed up for the test, but it can be quite tricky. If you no longer use your fire, we would recommend that you have it safely capped off and removed and the chimney professionally capped/blocked as chimneys that are rarely used do a very good job of keeping homes cool in winter, which is not good and is probably costing a lot of money that you don’t realise!
▪ Radiator pipes should be sealed where they emerge from the floor but, more importantly, where flexible piping is used and fitted through the plasterboard behind the radiators proprietary fittings should be used and additionally sealed if ill-fitting
▪ Skirting to all rooms should be sealed top and bottom including skirting to internal walls
▪ If wooden flooring or tiles are fitted prior to fitting the skirting, the plasterboard needs to be sealed against the floor and ideally the skirting sealed top and bottom once fitted
▪ Internal soil stacks should be sealed where they penetrate through floors or into the roof space, also where soil pipes enter the ‘boxed’ sections they should be carefully sealed
▪ Trickle vents should be removed or sealed prior to attendance of air test operative Kitchen
▪ Fit skirting behind kitchen units or seal between the bottom of plasterboard and the floor prior to fitting units
▪ Silicone seal where wastes and pipes penetrate through the plasterboard
▪ Seal around boiler flues/exhausts/vents where they penetrate the wall/ceiling Bathroom
▪ Bath/sink and toilet waste and water supply pipes should be sealed where they penetrate the floor or walls
▪ In some instances, ‘traps’ fitted beneath baths and specifically shower trays are ‘cut’ in to the floor to allow for their physical size and to make fitting easier. The cutting away of sections of flooring for this purpose causes serious air leakage and should be avoided where ever possible
▪ Bath and shower panels should be fitted and sealed once all pipework and holes behind them are properly sealed up.
If you would like to share your experience and test results with us, please email airtest@zerocarbonworld.org
Thanks for reading and helping reach a Zero Carbon World a bit sooner.
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Remember heating for homes in the UK contributes 26% of all CO2 emitted in the UK of which around 80% of which is met by burning gas.
by ZCW Trustee Dean Fielding