Posted By: AberborthinBrick walls will absorb water and the wind will then cool the bricks as the mosture is evaporated. A rendered or other wall that is "waterproof" will only have any moisture that has not run off the surface to evaporate and cool the wall - a much smaller amount than some bricks that will / can have the whole thickness saturated with moisture.

PHPP ignores heat loss due to evaporation from the external surface of the building but it does includes heat loss due to evaporation from clothes drying inside the thermal envelope!

Posted By: davidfreeboroughIf we are taking this into account then shouldn't we also account for solar radiation?

Most renders are light in colour, I guess this is to reduce damage caused by the sun. Bricks have a wide range of colours & the dark red ones on the south facing walls of my current house are noticeably above ambient air temperature when the sun is out.

David

PHPP does allow for the solar absorption and emissivity on walls/roofs for precisely this reason although exactly how it is factored into the calculations is unclear. I also haven't looked to see what sort of impact it has. I guess that on a modern well insulated house it must be minimal, but PassivHaus certainly thought it was important enough to worry about.