Indoor Air Quality And Breathability

Perhaps the area where breathability matters most obviously to many people, is as regards Indoor Air Quality (IAQ) and the effect on human health. This issue becomes absolutely critical as we strive to make our buildings more energy efficient by airtight design. Airtight design is not about unventilated design. It is about ensuring no unplanned air leakage through the fabric.

Without a degree of airtightness, the insulation of most buildings is pointless. As we try to reduce heat loss through buildings to a greater and greater extent, the issue of airtightness becomes more and more important. Airtightness is not only about heat loss. It is also about the migration of moisture into the fabric of buildings, and potentially about loss of thermal performance and interstitial condensation.

Airtightness however also has a huge potential effect on indoor air quality. Indoor air quality is usually dealt with in building design by ventilation. Good ventilation design, construction and maintenance can, in the main, deal with the issues raised by air-tight construction.

However the question needs to be asked as to how easy it is in reality to achieve good design and construction and what are the longer term issues of reliance solely on a ventilation system for the quality of the indoor atmosphere.

If we are to construct buildings which have a design life of more than 10 years, and perhaps as much as several hundred years, then we need to think clearly about how we can ensure moisture control within the building structure itself, and not simply rely on mechanical apparatus, which requires maintenance, repair and eventual replacement.

The main issues which need to be dealt with as regards indoor health relate to moisture, toxins (including VOCs) and odours. There is a relationship between these areas, as even VOCs are more dangerous with levels of humidity outside the magic box of 40 – 60%. In fact, getting humidity levels to around 50% for most of the time will deal with most indoor air quality issues, providing that toxic materials are avoided as far as possible (and not only in building work but in all purchases, packaging, and household cleaning materials).

Credit; Neil May – Extract From “Breathability The Key To Building Performance”

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