Interior condensation should be expelled from school

16 October 2020 by Jason Quinn

If Leaky Buildings 1.0 was about rain getting in where it shouldn’t, then Leaky Buildings 2.0 is all about the build-up of condensation, such that it feels like it’s raining inside.

Building physics knows how to build schools that stay dry inside. But here we have another school with a roof that drips on the kids inside due to interior condensation (potentially from exterior air). Why can’t we get this right?

BRANZ investigated what was going on in this Dunedin school where it “rains” inside. I believe this is the third attempt to fix this problem.

BRANZ concludes, “A warm roof design is a better solution when there are high inside moisture loads, an air-leaky ceiling and a cold, shaded location.”

They also warn that, “The actively ventilated roofs we have used in the past to dry out roof cavities only operate during the day. They also only work when the sun heats up the roof deck and the cavity underneath, evaporating the stored water and expelling the moist air to the outside.”

Another article from BRANZ deals with the same issues arising in residential homes.

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