Cold roofing systems have been written out of building legislation in many parts of Europe but in New Zealand they continue to be used, albeit less frequently than before. In the commercial sector, most new builds now incorporate warm roof systems, but in the residential market, only very limited specifications of warm roofs are occurring.
Warm roof systems take the dew point to the exterior of the roof, where in cold roof systems, the dew point is inside the roof and sits above the insulation. This means condensation builds up on the insulation, creating dampness that seeps through the insulation and renders it ineffective over time.
The dew point, where warm and cold air meet and condensation forms, needs to be outside the building envelope to avoid issues around dampness, moisture and mould, Equus’ Rob Roxburgh says.
“This is particularly important in the residential setting where the effectiveness of insulation has a large impact on heating and cooling costs for the homeowner or tenant,” he says. “Just because we have always done things one way, it doesn’t mean that is the right way. Warm roofs are a much more efficient and effective way of building. They need to be used more and more now we have the knowledge and the technology to use them.”