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Airtightness
testing is also known as ‘air pressure testing’ or ‘air leakage testing’. In
this article, I use these terms interchangeably.
The Reasoning
Behind Air Tightness
One of the
largest contributions to CO2 emissions in the world is property both domestic
dwellings and commercial premises. This is simply because of the large number
of buildings using gas and/or electricity to keep warm. There are literally
millions and millions of buildings burning gas or using electricity to keep the
temperature high enough for human habitation. Millions of properties using gas
or electricity translate to a big amount of CO2 released into the atmosphere
from the burning of these fuels or the processes used to create the fuels in
the first place.
How Is Energy
Efficiency Achieved?
Many initiatives
increase energy efficiency through net-zero energy homes. These include cavity
walls, loft insulation, and the various materials that go into the building of
a house to current standards. One of the means of improving a dwellings energy
efficiency is by making it air-tight.
What Does It
Mean?
“Air tightness
testing is a means to quantify the extent to which buildings ‘leak’ air
through their envelopes (for example perimeter walls, roof, and floor slab).
Air leakage (also referred to as air infiltration) is a vehicle for energy
wastage, resulting from the increased loads placed on the space heating and/or
cooling systems by the constant uncontrolled flow of air through the building
fabric.”
Imagine you have
an empty water bottle and you put the lid on. If there are no holes in the
bottle, with the lid on, you have created a sealed unit with no air leakage.
Air will not pass in or out of the bottle. The bottle is air-tight. When you
apply this to a house, it means that if there is no means of air escaping, then
the house is air-tight. If a house is airtight then heat will remain in the
property for longer which will mean a property will use less energy to stay
warm. In fact, if a dwelling is air-tight, heat will be lost very slowly
through conduction.
The government
is not saying all houses have to be built airtight to the extent where with the
doors, controllable vents, windows, etc closed, no air passes through. Air
Tightness is a gradient starting from zero meaning no air passes through the
house when doors, windows, controllable vents, etc are closed and a limitless
number say a figure of 20 where there is still a flow of air greater than 0 but
not the same as if all doors and windows were left wide open.
This is why your
airtightness target (number) for a dwelling is never zero but a fixed number
says 5. An airtightness number of 5 means that air is still able to leak from
the building but only a small amount of air leaks once all the controllable
vents, doors, and windows have been closed.
Why Do you
have to have an Air Pressure Test?
The government
has made it law in England & Wales that for a building to receive a
completion certificate, it has to have an airtightness test.
How Is an Air
Pressure Test Done?
The air pressure
tester will take measurements of the property and the environment such as the
floor area, envelope, and internal volume of the property. He will take
environmental readings such as internal and external temperature and barometric
pressure and wind speed. There is more than one way the test can be done but
all methods use blower door and fan technology. A common method is to suck the
air out of the property forcing air to be drawn from the outside into the
property. The fan has devices that measure the amount of air that is sucked in.
Air pressure is interpreted in conjunction with how much force the fan has to
exert to pull that air in. The reasoning is that the more air-tight a house is,
the less force the fan has to use to achieve the desired air pressure. The
information is also read in conjunction with the size of the property. These
factors are entered into a computer program that produces the airtightness
testing result. If you are looking for the best net-zero energy homes advisor
near you, we can give you the best solution to your need.