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John: Two topics that often get overlooked in
Australian construction are air
tightness and insulation completeness.
More emphasis is coming on build
quality, not so much what you build with,
but how well you put everything together.
Most of the developed world have started
to get a handle on this. They build more
airtight, they inspect during
construction,
they then test and make sure they've
ended up with a good result. In the UK
every single house has to meet a
requirement for air tightness and they
test with the blower door to prove it. In
most states in the U.S. it's the same,
from cold climates to mild climates and
even hot climates. The more insulation
used in our buildings, air tightness also
becomes a more important. It just makes
sense. Why pay to heat and cool your home,
and then just let the air leak out?
There's a lot of problems associated
with doing that. If it leaks air, it might
leak water. If it leaks air it's going to
allow bugs in. Air leakage wastes money on
power bills.
There's no good argument for air leakage
through the building envelope itself,
whether it be your floors, your walls or
your ceilings. Once you seal a building
up well, you can add some effective
ventilation, and then it all finally works.
Build Tight and Ventilate Right.
Today we're going to do a blower door
test on a typical new build with Phil
Alviano from Master Builders. Phil: Thanks John,
and I wanted to ask you today, when we're
doing a blower door test, what does it
actually help us with, or what does it
tell us about a house? John: We're simulating
around about 32 km winds on all
the facades. Phil: So once we've got the blower
door running, we can wander through the
house, we can have a look and try
and find where those leaks are, and those
drafts, and they're
the sorts of things caused, I guess, when
we're not putting a an effective air
barrier around the outside of the
building. John: When we talk about doing a
blower door test to look for a leakage,
what does that actually mean? I mean if
you were to combine all the leaks
measured by a blower door how big would
that hole actually be? Well, let's look at
the maximum and leakage allowed when you
use a blower door for compliance with
sealing requirements in their 2019 NCC.
That's a permeability of 10 at blower door
pressure. For a typical house, that level
of leakiness would need a hole the same
size as a standard window open by around
about 200 to 300mm. That's a pretty
large hole to have permanently open in
your building during hot or cold weather.
Spread over a whole house, it's about the
same size as having a dollar coin sized
hole in every square metre. That wastes a
lot of heating and cooling energy making
your energy bills larger, and the people
living in the home uncomfortable.
When you're trying to build tighter,
you've got two kinds of leaks to deal
with. The big ones, which are usually
individual ones, those are like leaky
manhole hatch, holes behind cabinetry, or
even a door with the poor seal. Then you
have little ones, lots of little holes
that are spread all over your house. They
require different approaches. Take an
obvious one. Your front door or your
internal door to your garage, which
usually has no door seal installed. That
lets in hot or cold air depending on the
season, as well as odours. Bugs can also
come in from this point as well. Taking
care of these is as straightforward as
getting a weather seal kit for your
doors. This one should be obvious too...
Bathroom fans should have a draught
stopper on them to seal them shut when
they're not in use. In fact, it's required
by code now. When the fan isn't running,
it shouldn't be leaking air out of your
house. A good bathroom fan, like this one,
will have an integrated draught stopper
that stays shut when the fan is not
running. You can also buy them separately
to retrofit an existing exhaust fan.
The roof manhole without a seal.
This thing lights up with air leakage on
infrared thermal imaging during an air
tightness test. It also usually doesn't
have insulation installed above it, but
it's so easy to fix. Some compressible
foam seals will make this into a
non-issue. Just put the seal around the
opening and the cover will rest on it
providing a good seal. As we walk
around at home, some of these leaks can
seem to repeat over and over. One really
annoying one is downlights. Make sure you
buy a light fitting that is rated for
insulation to be in contact.
They're usually sealed tight for air
leakage and insulated. Older lights are ones
that aren't insulation contact or IC
rated,
can use something like this down light cover.
It's fireproof, makes a good seal and
even provides some insulation value. There
are many things that can be done to
improve the performance of homes, and
blower door testing can help people
understand where air leakage is
contributing to a poorer performing
building envelope. Air tightness testing
is coming to Australia eventually. Let's
get ahead of the game.
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John: The future of residential building in
Australia will be strongly influenced by
consumer demand for energy efficiency,
comfort, climate resilience and quality.
Both the Building Codes Board and
Australian governments, are committed to
the COAG trajectory for low energy
buildings, and this will affect building
regulations including the NCC. Builders
will be expected to place increased
emphasis on meeting and proving energy
efficiency compliance. You'll be asked
more and more to understand and deliver
both code compliance and long-term
building health and performance. You will
need to: Build Tight and Ventilate Right.
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