New research favours inclusion of blower door testing in NCC
New research released by AIRAH’s Building Physics Special Technical Working Group makes an economic case for the incorporation of blower door testing of building sealing into the National Construction Code.
AIRAH’s study analysed the current performance of Australian homes and the issues that contributed to poorly performing buildings, and also laid out the methodology for correctly sealing residential dwellings. The Improving Australian Housing Envelope Integrity report reveals that homes can achieve between $1.80 and $2.60 in economic benefit for every dollar spent on testing.
A key finding was that improvement of air tightness combined with appropriate natural ventilation strategies could result in a reduction of up to 43 per cent in latent cooling peak load in Australian capital cities, and the use of blower door verification could result in a reduction in carbon emissions of up to 33,360 tonnes a year.
AIRAH chief executive Tony Gleeson explains that the Building Physics STG aims to bring building science principles, guidance and standardisation to the mainstream Australian construction industry.
A CSIRO research showed many Australian homes weren’t performing to their predicted rating, and also highlighted recurrent issues around building envelope construction and integrity in relation to air leakage and moisture control. Better performance can be achieved by following the construction practices already within the NCC.
Blower door testing or the use of fan pressurisation as a performance based verification measure gives the builder flexibility in terms of materials and methods used to meet the requirements.
President of the new working group, Jesse Clarke explained that members will focus on airflow and moisture migration through the building enclosure, with correct integration with HVAC systems to maintain thermal performance, acoustic performance, water ingress and healthy conditions in all classes of buildings.
Key recommendations include implementing a performance target of 10 air changes an hour as a performance-based measure in parallel with acceptable construction practice in the 2019 NCC code revision; AS/NZS ISO 9972 used as the standard test methodology to validate the performance; and a performance-based benchmark in parallel with acceptable construction practice until the 2022 building code update where performance verification becomes the only option.