How Do You Know If Your Passive House Works?
Passive Homes Need Testing
One of the main goals of a passive home is to reduce the energy demand for heating by 90%, one element that has a major impact on the required heating demands of a home is how much air is exchanged from outside to in/the air tightness of the home.
A standard home has 4-6 full air changes per hour - the house we are currently building has 0.32 air changes her hour. We’ll go into what this means for you in terms of comfort levels and heating and cooling costs in an article to come.
There are a number of tests that we perform throughout the building process to make sure your house truly performs as a passive house should. Not only saving you a tonne of money in heating and cooling, but also providing you a healthier home with better air quality.
It all starts with the design process, along with the materials and techniques that we use, relative to a ‘standard’ build. Passive home building is different. We use different materials, techniques and products at every stage of your build to ensure the layers of efficiency truly stack up when put to the test.
One of our favourite performance measures for a passive home
A blower door test is a diagnostic tool used to measure the airtightness of a building. In a passive home, the purpose of the blower door test is to determine how well the building envelope (walls, roof, and floor) is sealed against air leakage.
Getting ready for a blower door test
Believe it or not, we use incense. No joke. We have burley builders walking around the inside of the build. If we see the smoke from the incense change direction, it shows us a weak point in the vapour and air control barrier, where we could improve on the buildings air tightness.
What is a blower door test?
During a blower door test, a powerful fan is mounted, generally onto an exterior door of the home. This creates negative pressure inside the building. This negative pressure causes outside air to infiltrate the building through any weak points. That is any cracks, gaps, or even slight air leaks in the walls, roof, or floor. The blower door test measures the rate of air infiltration, which is a key indicator of a building's airtightness.
By performing a blower door test in a passive home, we as builders can identify areas that need improvement. If the test goes well, it is a special moment to share with the homeowners, that they are one step closer to having an incredibly efficient and healthy space they get to call home.
This can help improve the home's energy efficiency, indoor air quality, and overall comfort. Airtightness is a critical component of a passive home, which is designed to minimise energy consumption and maximise occupant comfort through highly efficient insulation and ventilation systems.
The ideal result for a blower door test depends on the specific standards and goals for the building in question. We work on performance builds as well as fully passive homes. In general, a lower air infiltration rate is better, as it indicates that the building is more airtight, thus requiring less energy to heat. This is something we try to incorporate into every build we do.
Passive home performance levels
In passive homes, the recommended air infiltration rate is typically much lower than that of conventional homes. Passive house certification requires an air infiltration rate of no more than 0.6 ACH50. Achieving this level of airtightness requires careful attention to detail during construction and the use of high-quality materials and insulation.
We were absolutely stoked to hit a rather epic 0.32 on our recent blower door test on our build in the heart of Wanaka. This level of air tightness signifies the building having the potential for an incredible level of energy efficiency – above and beyond what is needed as a passive home.
If you’re curious about building a passive home and knowing more about the process (like blower door tests) get in touch. We’re incredibly passionate about what we do and how these passive home principles and techniques are slowly filtering through and improving New Zealand building standards.