Nowadays houses must be draft-free and air tight. We used to place foam strips between the logs, this took care of the draft but it was not fully air-tight. Today we take a more rigorous approach: we completely wrap the house in an air-tight foil. Damp-open, but air-tight. We started wrapping yesterday, at the same time we are placing the main beams on the roof. These are maybe a little over-dimensioned, 60 kilos each, fully laminated, they will never bend.
End of February 2018 we posted some photos of a foundation where we would soon build a new log house. Now we are in June, and we can show some more photos of the progress so far.
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?