Sealing a building is one of the most overlooked components of Sustainable building in Australia, but it is an integral part of the Passive housing concept and one of the most important tests to be Passive House certified.
Living in the city of Adelaide, have you ever wondered why, on a hot day when you run your air conditioner for hours on end and then turn it off, the room heats up again in a matter of minutes? The cold air inside is continuously escaping outside, while the hot air outside, is finding its way through all the gaps in your building and the same is true in reverse for winter.
Insulating your home is the first step, but thermal leaks and sealing a building are important too.
The first diagram above indicates typical areas air passes back and forth between your walls, windows, doors, and roof.
The second diagram shows where most of that energy is lost in those areas, interestingly, fans and vents, which would seem the obvious source, are responsible for less than 5% of the leakage in a typical home. Gaps between wall frames and floors, wall frames and ceiling and around windows and doors are the typical culprits and timber framed homes are particularly susceptible to this type of leaking.
Gaps between walls and windows, and walls and doors are one of the easiest areas to change in a construction method, using either expanding foam, or a physical seal such as a flashing can significantly reduce the possibility of air passing through around these frames.
The best and easiest way to test how well sealed your existing, or new home is using what’s called a ‘Blower Door Test’. In this test, the operator sets a big fan on one of your doors, then shuts all the doors and windows and pressurises the house.
They then record in the space of an hour, how many times they have to ‘refill’ your house with air at that pressure. The corresponding number of air changes gives you the value of your home.
The typical Australian home has to be refilled at least 10-20 times during the course of an hour, while the Passive House Standard for certification is 0.6.
It is plain to see just how far behind typical Australian building practice is with this kind of data and while not every home will be able to reach the passive house standard, an energy efficient home that performs at 5 or less changes an hour will contribute huge energy savings for the Adelaide homeowners and a considerably more comfortable environment to live in.