ᐅ KfW-55 house experiences significant cooling

Nadini89 schrieb:
I’m just wondering if a new house is allowed to cool down that much in such a short time...

You can’t generalize on that.

If it’s colder outside than inside, every house cools down, no matter how well insulated it is, unless some heat source is present. This can be heating, sunlight, body heat, or electrical devices (cooking, lighting, etc.) inside the house.

To answer your question, it would be more helpful to observe how quickly the indoor temperature drops, for example overnight.

Do you have no (south-facing) windows, or are the blinds kept closed during the day? 19°C (66°F) in the living room after a day like today is already low. We lowered the external blinds on the west-facing windows in the afternoon because it got too warm. Rooms with south-facing windows in our house still have about 22°C (72°F) in the morning, other less-used rooms are around 20–21°C (68–70°F).

Your ventilation system probably has heat recovery. With some units, you need to manually switch the heat exchanger from summer to winter mode. Check the temperatures at the supply air vents.

Maybe the building still contains a lot of residual moisture, which uses energy. Is the house built with solid construction or wood?

What type of construction method is being used? Are you sure nothing is getting through if I tell you that the upper floor only cooled down by 0.7 degrees Celsius (1.3°F) overnight?

You mention a ventilation system, but there are also systems without heat recovery.

And please do not compare it to an apartment. When neighbors heat their units, they indirectly warm an unheated unit as well. Basically, you need an apartment located in the middle that requires almost no heating.

Maybe the bypass in the controlled ventilation system is still open at night? That would cause the temperature to drop even faster.

I had also suspected a bypass at some point. Last night we had 3°C (37°F), and during the day it was 20°C (68°F) outside. Inside the house, through the windows, the temperature warmed up to 24°C (75°F). During this transitional period, a fireplace is really great—we don’t have one yet, but my neighbor has already started using theirs. For example, I’m not that sensitive to cold, but my wife has already brought out her pajamas with socks.

Bypass, or in our case a summer cassette, cooled down by 2-3 degrees Celsius (36-37°F) at night. The week before last, nighttime temperatures were between 4 and 10 degrees Celsius (39-50°F). I replaced it just one week ago.