ᐅ Low Moisture Levels in New Construction?

Created on: 11 Apr 2023 20:41
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NewHouseAppear
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NewHouseAppear
11 Apr 2023 20:41
Hello everyone,

We have now been living for about 4 months in our KfW 55 new build with a heat pump and underfloor heating, constructed with Poroton (36.5cm (14.4 inches) monolithic), but without a ventilation system. During the roughly 10-month construction phase from January to November, we ventilated thoroughly, usually opening the windows wide 3–4 times a day, in the mornings and evenings, for extended periods.

From stories and many reports, we were quite worried about mold in the new build, which is why we ventilated so often. However, since moving in, we have consistently observed 40–60% humidity in every room, even in unheated basement rooms. We are still ventilating regularly, but we are somewhat surprised because we have often heard that new buildings retain construction moisture for months or even years.

Have I misunderstood how residual moisture works, and do we basically already have an ideal indoor climate? Or do the hygrometers simply measure the air humidity in the room but not, for example, the moisture in the building structure?
andimann11 Apr 2023 20:49
Hello,
NewHouseAppear schrieb:

stable 40-60% humidity in every room since moving in,

That’s quite humid already. We are in winter, so usually you can expect about 25-40% humidity. It takes some time. But up to 60% is not critical.

Best regards,

Andreas
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xMisterDx
11 Apr 2023 22:16
If you don’t ventilate for a week, you’ll quickly realize how much moisture is still present in your new build.
Just kidding, of course. Keep ventilating regularly. However, I wouldn’t describe 40-60% relative humidity as “quite humid.” That is the optimal indoor humidity level for living in a house. I definitely wouldn’t want to live with around 25% humidity...

Since you built during the summer, there is surely still a significant amount of residual moisture in the house. Starting construction in January likely means you had the screed poured around July/August and then started heating it? At that time of year, even with windows open 24/7 to create a draft, it’s difficult to get moisture out of the house.
Ventilate, ventilate, ventilate.