A look at the evidence on mechanical ventilation

Natural ventilation often fails – but what is the evidence that mechanical ventilation succeeds? – Investigation for Passive House Plus

There have been a number of studies showing that natural ventilation, dependent as it is on random gaps in the building fabric and the vagaries of wind and weather, is not a reliable source of fresh indoor air. (see here for my article on this)

In theory, mechanical ventilation is under more control, and should work more reliably. But does the evidence bear this out? Does mechanical ventilation deliver good air quality in practice?

I looked into the research to find out whether MVHR, in particular, lived up to the ideal.

What I found was that at its best, mechanical ventilation is both effective and comfortable – with occupants often reporting that they perceive their health to have benefited too.

However, both comfort and indoor air quality were dependent on the quality of the installation. And the two are closely linked – a poor installation is likely to be uncomfortable for occupants, who are likely to turn it down – or even off – with predictable consequences for air quality. By contrast, systems that had been properly commissioned – as required in the Passivhaus standard — tended to be relatively quiet and comfortable.

The full article is available to read (free) on the Passive House Plus website, here. (First published Nov 2015)