64 INSULATION
Air leakage. It doesn’t matter how low your U-values are if there are draughts
Icynene H2 Foam Lite spray applied insulation from Huntsman Building Solutions
Over 60% of UK housing stock was built pre 1960’s when little thought was given to heat loss prevention
P
addy Leighton of Huntsman Building Solutions-Icynene, Spray applied insulation, explains why
minimising air leakage must go hand in hand with better insulation. Better insulation of domestic households is
seen as one of the most important ways of reducing carbon emissions and slowing the effects of climate change. A recent environmental audit select committee report says that 19 million UK homes are poorly insulated that unless urgent action is taken to improve energy efficiency of homes, the UK will fail to meet its climate targets. Unfortunately, as over 60% of our current
housing stock built pre-1960 when little thought was given to heat-loss prevention, the challenge is significant. Overall, roughly 20% of UK carbon emissions are generated through heating, hot water and cooking in domestic properties. Even more troubling was the fact that in 2017, emissions from buildings actually rose by 1% over those of the previous year.
Basic principles If we go back to basic principles; heat loss in a building occurs through a combination of four processes: conduction, convection, radiation and mass transfer. The colder the
outside temperature, the warmer the inside, and the worse the thermal insulation of the building envelope, the greater the heat loss will be. In the UK, the construction industry
focusses primarily on U values – sometimes referred to as heat transfer coefficients – as a measure of conductive heat loss. These are used to measure how effective elements of a building's fabric are at insulating against heat loss. The lower the U-value of an element of a building's fabric, the more slowly heat is able to transmit through it, and so the better it performs as an insulator. Very broadly, the lower the U-value, the
less energy is required to maintain comfortable conditions inside the building. Unfortunately, measuring the thermal
efficiency of a structure by U-value alone fails to take into account of heat loss through air leakage. If you spend any time in high mountain environments you quickly realise that it is the wind that strips the heat from your body. And it is the same in buildings. It doesn’t matter what your U-value is if there are draughts. Traditional forms of insulation are relatively inefficient in preventing air leakage through draughts. They can’t completely fill the complex voids in roof structures or seal the interface between the insulation and the
building components. They can also struggle to cope with small structural movements which can lead to air gaps. When 40% of a building’s heat loss caused
by air leakage, an insulation system that works to prevent air leakage – effectively creating a “sealed box” environment, is essential to minimise heat loss.
Spray applied insulation effectively seals the complex voids in a building structure
WWW.ARCHITECTSDATAFILE.CO.UK
ADF JULY 2021
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