Modern house design typically follows the mantra “build tight-ventilate right” with low air infiltration and high thermal performance. Efficiency is what we should be striving for, but what does this mean for indoor air quality? Historically, home indoor pollutants (e.g. water vapour, cooking smells, chemical fumes) escaped through gaps in the building fabric via passive (natural) ventilation. Today, trickle ventilation and increasingly whole house mechanical ventilation systems (e.g. MVHR) are used.
MVHR has been criticised for installation noise and the "perception" of draft and dry air as recurring problems. There is also a concern that should this system break down and the occupants cannot afford to fix it, or maintain it, that serious indoor air quality problems will inevitably occur. The largest advocate of this approach is Passivhaus which supporters argue substitutes a heating system for a more sustainable ventilation system which includes heat recovery. But is this the only modern design solution for ventilating our homes?
In 2002, the architect Bill Dunter completed BedZED, a zero carbon housing development that uses passive stack ventilation with heat recovery system. Although his solution is a very prominent wind cowl (not appropriate for every home design) it does prove that a passive approach to ventilation is possible.
Whilst the MVHR approach is feasible and increasingly widely used in the United Kingdom, I can’t help thinking that the long term solution to reduced energy use in homes should be a passive approach, perhaps using lessons from history:
“Passive design and function are low carbon principles that older structures relied on. Low carbon buildings should not be packed with gadgets and kit, because if they are sufficiently well designed and configured they should not need it. Traditional buildings demonstrate this amply!” Historic Scotland
Should passive mean non-mechanical or do we need to find new solutions to contemporary problems?
Credits: Images and data linked to sources.