Paul Jennings from ALDAS talks through some of the findings from the airtightness tests we carried out as part of our documentary.
Watch Our Brand New Documentary!
The Future of Housing – And How Airtightness Can Help got its first screening at the Mildmay Community Centre on Thursday 4th December 2014.
Thank you to everyone who came along. There was a real passion in the room.
Interview with Paul Jennings
The First Test was of a Draughty 1950’s Brick Built Semi
This property was of particular concern because one of the residents was disabled, so there were real health benefits to be realised from improving the comfort of the home.
A Huge Fan Sucked Air Out of the House and Then a Search was Carried Out to See Where it was Coming Back in
Some of the locations where leaks were found were to be expected, such as the loft hatch, however the extent of others such as the bay windows and window sills were a surprise.
By exaggerating the draughts they could be detected using a number of methods: feeling them on the back of the hand, using stage smoke and an anemometer to measure how bad they were.
Remedial Work was Carried Out and the House Re-Tested
A team of specialist sealers came to fill the gaps with sealants and expanding foam and replaced the poorly performing window sills, resulting in a reduction in air leakage of 25% before the work was even completed.
Paul reminds us that houses are subject to maintenance anyway, but concedes in using these products there is a degree of trade-off between environmental friendliness and speed and ease of application. However the durability of the products potentially providing an extra 20-50 years on the life of the building should be compared to the environmental impact of what you would have to do to replace the house if it was deemed completely unusable.
The Leaks Were a Combination of Pre-Existing From the Time the House was Built, Together With Flaws in Refurbishment Work
Leaks where electricity cables come into the property have probably been there from day one, however the problems worsened when window replacements were poorly fitted and left gaping holes.
Such refurbishments will make properties subject to moisture problems and mould in the walls. Interstitial condensation in the fabric of the building in particular can be particularly damaging to timber frame buildings.
The Second Property Tested was a Developer Built Home, Less Than 10 Years Old
Paul notes the irony of this being supposed affordable housing, when in reality the homeowner couldn’t afford to heat it, despite it conforming to building regulations. Alarmingly this modern home performed worse in the testing than the 1950’s house.
The Building Regulations Relate to Building Safety, Rather Than Comfort
This house recorded an air permeability reading of 9 which falls within the building regulations maximum of 10. What was apparent from the test was that the building regulations are the lowest common denominator which are not fit for purpose when it comes to providing a comfortable quality of life for the resident. Paul makes the point that volume house builders are continuing to build inadequately, so homeowners are going to have to spend a considerable proportion of their disposable income on heating.
With Some of the Leaks Sealed, Sometimes the Air Just Takes a Different Path
The testing ultimately measures the resistance to air getting through the holes. When some of the biggest leaks have been stopped sometimes some of the other ones, which may have a greater resistance, might start leaking. However it’s an incremental process which you can keep going with.
Airtightness Testing Should be Carried Out Before Refurbishment
Paul explains that there is already a lot of knowledge and understanding to help inform what you’re planning to do. He believes the government have wasted a lot of money by investing in insulation materials without thought to making buildings airtight. The air just goes through the insulation and takes the heat away.
An Air Permeability Level of 3 or Even Lower Will Still Provide Adequate Ventilation
More than enough ventilation at this level can be provided by opening windows, natural occurrence around gaps and cracks and even just by coming and going out of the front door. The exception to this is where there are open or gas fires which still require a source of air combustion.
Lower than that and consideration would need to be given to extract fans in wet areas. Below a level of 1.5 will be a pretty airtight property which will require some form of sophisticated mechanical heat recovery system.
It’s Relatively Easy to Achieve an Air Permeability Level Between 5 and 3 For Most Properties
This would probably be halving it in most properties and could be achieved without too much disruption. A barrier to this would be what people could afford to invest in their property.
There would be little incentive for a tenant in a rental property to invest heavily, though Paul points out that there are still measures which are cheap and effective that would make it worthwhile for them to do.
Paul's Demonstrator Acts as an Effective Visual Aid to Assist People's Understanding
People are generally amazed with the results that the demonstrator produces. It gives examples of the vulnerable areas where leaks occur and also shows the same areas taped and sealed effectively. Often people can’t appreciate air leakage until they’ve actually felt it on their hand.
Ashley Vale was an Interesting Case Study of a Group Self Build Scheme
Ashley Vale was conceived and built at a time when there was very little awareness of airtightness and before it came into the building regulations. While it was built with sustainability as its focus it could be in the future that because of the high levels of insulation it will face problems with moisture condensing in the walls.
A Weakness in the System is that Building Control Don’t Test Every House
Paul mentions the Lancaster co-housing scheme where every one of the 44 houses was tested for airtightness and achieved the Passivhaus standard. By contrast, in mainstream construction Building Control only carry out tests on sample houses, meaning that builders are not being held to account.
A National Database Could be a Helpful Way of Sharing Information About Airtightness Related to House Types
While there will always be variations caused by modifications, there will still be airtightness issues which you would expect to be common to particular types of houses. A database could give information on where they leak, where the problems are in the insulation and what has and hasn’t worked in fixing them.