Airtightness

The enhanced fabric energy performance of masonry construction has been achieved through a range of measures including higher standards of insulation, airtightness and thermal bridging. However, one credential that remains unaltered is masonry’s inherent thermal mass, which can boost the performance of low energy heating systems and also provide some useful resilience to overheating in new homes.

The average air tightness of new masonry dwellings has steadily increased in recent years as knowledge gained through pressure testing has informed the design and construction process. An air permeability rate of around 5 m3/(h.m2) is now fairly standard, with better values being achieved when required. In fact, results from pressure testing of all types of housing construction over the last few years show that those achieving an air permeability of 3 m3/(h.m2) or better were mostly masonry with a wet plaster finish.

Masonry provides the basis for a robust air barrier that is not reliant on tape/sealant, and will not degrade appreciably overtime. If required, blockwork can also be wet plastered or parged to enhance performance. A study of aging and airtightness published by the NHBC Foundation includes pressure testing results that suggest masonry homes remain more airtight over time than timber frame construction. It should be noted however, that the sample of homes examined was relatively small (for more information see:
Ageing and airtightness - How dwelling air permeability changes over time”  (published by the NHBC foundation).