Air leakage: The next big insulation test

According to Natural Resources Canada air leakage represents 25-40 per cent of the cost of heating and cooling a home while the US Department of Energy puts the cost at 30 per cent or more. 

Given that energy costs are rising, it is perplexing that Australian governments have not given any attention to this major loss of comfort and unnecessary cause of household financial strain.

With the ending of Rudd's successful housing insulation program, where over one million houses were insulated and safety in the industry was improved (contrary to lies being spread in certain quarters), it's now time to not only bolster the promotion of insulation and reinstate that program but to create a parallel program to seriously address air leakage in our buildings.

In Europe air leakage tests are mandatory in a number of jurisdictions including Sweden and the UK where PART L1A 'Conservation of Fuel and Power' of the building code requires air pressure testing at all new developments.

In a study conducted by Air Barrier Technologies in 2011 for the Victorian Building Commission, houses built prior to July 2005 before mandatory star ratings were introduced averaged 2.25 ACHnat (air changes per hour at natural ambient) while the worst performers were changing air as much as five times per hour. For those of us unlucky enough to live in a house that changes air more than three times an hour, from an energy performance perspective it's almost the same as living outdoors in a tent.

The situation, however, has marginally improved with regards to houses that were built after star ratings came in where the study found that average was just under 1ACH and the worst performers were 1.9ACH and the best were 0.5ACH.

The US DoE target for air leakiness is 0.35 ACH, a minimum figure that we should adopt in our building codes. 

The reason I say we should use that as a starting point is because that target is higher than is necessary, as it includes houses that use fossil gas in the kitchen or include gas heaters that are either unflued or have their air intake from the living space.

A lower figure is justified once we logically shift all new build developments to all electric including induction cooking, heating with reverse cycle air-conditioners and heat-pump hot water.

The importance of air pressure testing is shown by an example in 2008 where a 200sq metre seven-star house was built by a large volume builder in Lyndhurst, Victoria. Despite having high performance in mind with some application of passive solar design principles, double glazing and significant insulation the house was still leaking like a sieve with about 1.8ACH, that's five times more ACH than is ideal.  Following testing, the building's performance was increased significantly with the addition of draft sealing, ceiling fan dampers using commercially available strips and caulking of air gaps which were identified through the use of blower door and smoke tracer pencils. 

According to the NATHERS rating system a 7-star rated home should use no more than 83 MJ/M2/year for heating and cooling but with an ACH of 1.78, the Lyndhurst home was using 293 MJ/M2/year and it was really performing like a 2.5 star home.

According to the builder if the air leakage had been done during construction it would have cost an additional $600 and would have saved the householder around $400-500 per year on energy bills (adjusted for 2013 energy prices).

In Germany, houses conforming to the PassivHaus standard are built almost airtight and to be certified must achieve 0.01ACH in a blower door 50pa depressurisation test. In these houses and other very tight houses a mechanical HRV (Heat Recovery Ventilation) system is required (not to be confused with a poor performing space heating system from NZ with the brand name HRV).

At the moment Australians are spending hundreds of dollars a year unnecessarily heating the atmosphere outside their homes.

Even with a kludge fix of bigger heating systems to get around this houses with these problems (by far the majority) aren't comfortable because draftiness, particularly when its cold outside, gives an unpleasant sensation on the skin.

Matthew Wright is the executive director of Zero Emissions Australia.

Since 2006, Building Regulations in England and Wales and Northern Ireland have required mandatory air leakage testing of new homes. Regulations in England & Wales were further revised in October 2010. Since October 2010, for new building warrants, air leakage testing has been a mandatory requirement in Scotland.

Air tightness, air leakage, air pressure, blower door testing is mandatory in the UK. Guides are available showing how to approach appropriate air sealing for Canada and the US.