Passivhaus – architectural ‘eskies’: no mould
The Building Code of Australia (BCA) sets a bar for minimum building performance, with the new 2015 edition raising this bar once again. However, the BCA requirements to better insulate and air-seal our buildings is now often resulting in mouldy and hence unhealthy buildings. This does not need to be the case.
Effective and trusted solutions have been developed overseas and are presented briefly in this second of a three-part series about the European ‘Passivhaus’ standard by Andreas Luzzi.
While environmental pollution control and abatement have been making great technical progress over the past decades, our indoor environments are going the opposite way again. This is mainly due to microbial challenges, not due to indoor pollutants.
Most obvious is the resurgence of mould in our homes and apartments. This is the direct result of BCA-compliant albeit
“inappropriate construction methods that defy fundamental laws of (building) physics.”
Bacteria and particularly mould spores grow well in moist and warm environments. Our buildings provide ample breeding grounds during the colder periods of the year.
What is now happening on a large scale throughout Australia is that the combination of ‘old-fashioned’ construction methods with new building performance demands has ended up shifting the dew-point from previously visible indoor areas right into walls and roof, hidden behind the gyprock lining.
This is not only jeopardising the structural integrity of the building fabric over time (rotten structural framing), but it also allows growth of significant amounts of mould within the building fabric. This was the case in the northern hemisphere back in the 1980s and 1990s, when mould-related respiratory health problems increased significantly
These days, New Zealand has advanced as OECD’s asthma-world-leader, not because of its pristine outdoor environment but simply because of sick buildings.
Crucial elements of the passivhaus standard
With the benefit of hindsight, it is rather simple to omit any mould in buildings forever. The European ‘passivhaus’ standard has proven this for 20+ years.
Three things are crucial. Firstly, the building envelope has to become truly air-tight. This is best achieved by employing moisture-controlling membranes such as ‘intello-plus’ under the gyprock and taped everywhere. Blower-door tests are perfect tools to check air-tightness.
Secondly, thermal bridges must be eliminated. High thermal-conductivity materials such as steel and concrete are not allowed to run through the building fabric, generating cold thermal bridges. Constructing in timber or else employing structural thermo-breaking technologies eliminates any thermal bridges. Infrared cameras are wonderful tools to visualise sinful thermal bridges.
Thirdly, smart ventilation is needed when the building is closed up to keep cold or heat out but to allow fresh air in. A myriad of high-efficiency energy recovery ventilation (ERV) solutions are now available on the Australian market. Operating like fully-filtered breathing lungs for the buildings, ERV systems recoup up to 90 percent of the thermal energy of the exiting stale air when bringing in fresh air.
Andreas Luzzi is CEO LAROS Technologies Pty Ltd. For more information visit www.laros.com.au.