Ventilation for sleeping room / sleeping rooms

Hello everyone,

I am new here and will briefly describe the situation related to the actual question.

Two years ago, we (my wife and I) built a KFW70 house (wood frame construction) without a basement. There is wood fiber insulation applied to the outside of the house, and we have no roof window, but the roof tiles are granite gray. Unfortunately, at that time I did not think to order the insulation above the roof. In summer, at very high temperatures, it does get noticeably warm in the bedrooms under the roof (high ceiling roof), which is bearable without a fan, but something should be done here.

My decision back then was against ventilation, as I did not want it (why is irrelevant). The windows have a window rebate opening and are regularly ventilated (several times a day).

Yesterday was a very warm day (peak outside temperature here 33.9°C) and in the bedrooms under the roof it was 25.8°C (which my wife definitely feels as noticeable).

Now I got the idea (since we always keep the bedroom windows open at night in such temperatures anyway) to install a kind of "ventilation" at the ceiling and vent it through the roof with a ventilation tile. The background is that warm air rises, and if there is no wind outside, cold air can still come into the room through the windows at night. I will handle the control and the installation theoretically myself.

I would like to hear experiences or ideas for and against realization here, possibly someone had the same idea and can report on it.

PS: I do not need heat recovery or such tricks. We live in the countryside and have a local heating network. I need about 12 MW per year, which is not much. I pay 4 cents per kW. It is really "only" about installing a fan in the roof that I control at night (via my PLC), which then "gets rid of" the warm air and "sucks" the cool air into the room at night or exchanges the air.

Thank you very much in advance.

Best regards

I would install valves in the ceiling and place the fans elsewhere, because when sleeping, any noise, no matter how quiet, is usually disturbing... and also size the fan(s) quietly larger, so they can run at half power and are quieter...

The problem is that in winter the valves have to be tightly sealed, otherwise you could have problems with condensation...

Hmm.. ok, thanks, I hadn’t thought of that yet. Theoretically, a [Mauerkasten] aka Aeroboy (which I installed in the kitchen and am satisfied with) would be the right direction. I’m just reluctant to install an "attic" or a part of one to minimize the noise. But it would be possible...

Pro and Con

If I understand correctly, you want to create a breakthrough through the building envelope (here the roof) in order to provide ventilation there. Goal: regulated and forced (unlike an open window), to supply cool night air. A sloppy execution could possibly (I don't know your roof structure) lead to construction damage (winter, airtightness, condensation, ...). So there is a certain effort involved ... Alternative idea: mobile air conditioner, run it in the afternoons on hot days to cool the bedroom.

Unfortunately I didn’t think of that back then and ordered the added roof insulation.

Is the roof not insulated at all? Although, then it would be significantly warmer ....

Hello Biber,

thanks for the hints. Yes, with the lift-and-slide door you are right, that it is not so easy to implement and that there is more to consider.
We already have a mobile air conditioner, I also ran it yesterday.
But when I see again that it is 15°C outside and 23.1°C in the bedroom, I would still like (even if it goes through the house wall and not through the ceiling) to continue pursuing the goal with the ventilation at night.

Regards