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Why build an airtight home?

Why Airtight?

Have you ever lived in a home that you struggle to keep warm when it's cold out and cool when it's hot? What about a home that's overly humid in summer or has a mould problem in winter? Are you asthmatic or have allergies?

If you're looking to build a new home and looking for solutions to these problems, introducing an air control layer and building an airtight home is most likely the answer.

When we can control the air that comes into our homes, we can manage water vapour and humidity while delivering healthy filtered air for premium internal air quality.

"Rather than thinking of the house as being airtight, think about a home that has the ability to control the air it contains".

What is an airtight home?

An airtight home is one that's been constructed in a way to include an air control layer as part of the building fabric. As part of this process, during construction, the house is pressurised to 50 Pascals. Known as a 'blower door test', this determines how airtight the place is. To give some examples, the average project home built in Australia is 15.4 air changes per hour (15.4 ACH). When pressurised, that equates to a volume of air leakage per hour, 15.4 times the volume of air in the house.

Globally, we see 5.0 ACH and less achieved by introducing better quality windows and simple air control details. With the introduction of a detailed air control layer such as Proclima Intello combined with good quality windows, we can see a house get well below the Passive House standard of 0.6 ACH.

How do you make a home airtight?

As mentioned earlier, introducing an air control layer to the building fabric will dramatically decrease a home's ACH. An air control layer needs to be continuous and includes the floor, walls, windows and roof (the building fabric). Known as a fabric first approach, designers and builders would dedicate attention to how junctions of the building envelope are constructed on-site. Tradesman will also seal all cables and pipes that penetrate the building envelope.

Once construction reaches a point where the rough-in of all services is complete, and windows are installed, the builder will carry out a blower door test pressuring the home to 50 pascals. The blower door test is the perfect time to check for and address any holes or leaks in the building fabric.

Image: Installation of Proclima Intello (air control layer) into a new build.

Can I breathe in an airtight home?

Many people struggle to comprehend the idea of an airtight home. They often fear and assume the home will be stuffy and stale. It is quite the opposite. Rather than thinking of the house as being airtight, think about a home that has the ability to control the air it contains.

For this, homes will include a heat recovery ventilation system (HRV). An HRV is a 'box' on the wall that supplies fresh, filtered, outside air to each habitable room while at the same time exhausting stale old air out of the home. A system such as Zehnder Q350 is what we generally install. It has minimal power draw, will run 24/7, and, of course, include heat recovery, making it a must for a high-performance home that desires minimal thermal losses or gains.

Image: Zehnder Q350 installed into our Certified Passive House in Buninyong, Victoria

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