We’re seeing increasing demand for high performance building envelopes, with blower door testing an essential tool to ensuring great results. But while it’s common practice in many parts of the world, we’re yet to see this important practice taking hold here in Aotearoa New Zealand. With demand growing, and Homestar v5 providing greater incentive for more airtight homes, here’s what you need to know about blower door testing.
Blower door testing is a diagnostic procedure for measuring a building's airtightness. It involves the use of a powerful fan mounted on an exterior door frame which depressurises or pressurises the building, causing air to flow through any gaps or leaks present in the building envelope. By determining the rate of air leaking in a building, energy auditors can make informed decisions about improving energy efficiency.
Modern blower door testing equipment and procedures evolved from the US in the 1970s, with building scientists developing the test as a standardised method for quantifying air leakage.
As energy efficiency regulations and building practices have improved, blower door testing has gained popularity. Today in many parts of the US, UK, and Ireland, a blower door test is required for new buildings, and it’s common practice across much of Europe. In Australia, air infiltration testing is included as a compliance pathway in the National Construction Code.
Why should a building be airtight?
There is often confusion about the healthiness of airtight construction. Well designed, airtight buildings are easier to maintain at a healthy indoor temperature year-round. They are less draughty meaning they leak less warm air and allow in less cold air, plus it’s easier to reduce condensation within the building envelope.
Good ventilation is a requirement for all buildings and must go hand-in-hand with an airtight building. Having an airtight envelope will help improve the energy efficiency of a mechanical heat recovery ventilation system.
You can also continue to enjoy indoor outdoor flow and open windows in airtight buildings. By design though, the doors and windows will be high quality and will prevent draughts when it’s time to close them.
Blower door testing in Aotearoa.
Here in Aotearoa New Zealand we do have a growing number of trained and experienced blower door testers, many accredited with the Air Tightness Testing and Measurement Association (ATTMA). A full list of registered air tightness testers is available on the ATTMA website.
Homestar v5 promotes and rewards airtight construction with points available for conducting a test and achieving a good level of airtightness. In addition, the Energy and Carbon Calculator for Homestar (ECCHO) shows designers how much impact building infiltration (or ‘leakiness’) can have on energy demand. The more airtight, the more energy efficient the building. Homestar designs hoping to model a home with anything less than the default 5 air changes per hour must also specify a blower door test.
For more details about airtightness in Homestar v5, download your copy of the Technical Manual or talk to a Homestar v5 Designer.
Sean Maxwell of ATTMA Australia shows a blower door test result from a test conducted by Richard Hollard of pro clima NZ during a recent NZGBC demonstration in Auckland.