One of the main discussion topics between builders and architects and construction engineers is: insulation, heating, humidity and ventilation. Especially in panel walls there is the problem that high insulation values create humidity in the walls, unless special techniques are applied to stop humidity to enter the walls.
Let’s design a very basic wall: gypsum on the inside, then mineral wool/glass-wool, then pine on the outside. Nobody builds like this, but let’s do it as an experiment. We want the wall to be very well insulated so we put 20 centimeters insulation between the gypsum on the inside and the pine on the outside. Here’s what the wall looks like:
Inside the wall are projected two curves: a black line with the temperature (view the Celcius scale on the left) and a blue line with the dew point, i.e. the temperature at which the humidity condensates.
As long as the black line is higher than the blue line: no problem. But as soon as the black line meets the blue line there is a big big problem: condensation. Meaning: fungus, rot, and badness. We don’t want the black line meeting the blue line. What to do?