New Zealanders have, over the last few years, favoured positive pressure ventilation systems, touted by HRV and DVS products. However, as the style of houses we build evolves, insulation envelopes become tighter, and more housing is built in high-density areas, ventilation and heating needs are changing too.
While positive pressure systems have their place, and provide reasonable performance in certain situations, they are becoming obsolete in many new builds and higher density living situations. As Richard Adams from The Heating Company
explains, positive pressure ventilation systems are only valid for older homes that have natural ventilation, not modern air tight homes.
“Positive pressure systems work by pushing warm air from the ceiling cavity into the home creating positive pressure, which then removes moisture from the house. While that is all very well, positive pressure systems take the heat out of the home while removing the moisture, so they are detrimental to your heating costs, which become higher when using this sort of system,” Adams says.
Because positive pressure systems move air from the ceiling cavity into the house, the air is stale rather than fresh air from outside. Also during the winter months, there is only a limited amount of warmth retained in the ceiling cavity so when the temperatures drop, positive pressure systems push cold air from the ceiling into the house.
“As houses become far more airtight than they were even a few years ago with insulation, double glazing and a tighter building envelope, you have to ventilate. If you don’t you end up living in an unhealthy environment.”
And that’s why Adams says specifiers are turning to different solutions and moving away from positive pressure systems that have been favoured of late.