Hello everyone,
I’m new here and will briefly explain the situation before my actual question.
Two years ago, my wife and I built a KFW70 house (timber frame construction) without a basement. The exterior of the house is insulated with wood fiber insulation, and while we don’t have roof windows, the roof tiles are granite gray. Unfortunately, at the time, I didn’t consider ordering additional roof insulation. During very hot summer days, it does get noticeably warm in the bedrooms under the roof (with a high ceiling), which is bearable without a fan but still something I want to address.
Back then, I decided against installing a mechanical ventilation system, which I preferred not to have (the reason is not important here). The windows have a casement opening, and we ventilate regularly (several times a day).
Yesterday was a very warm day (peak outside temperature around 33.9°C (93°F)), and in the bedrooms under the roof, it reached 25.8°C (78°F), which was noticeably uncomfortable for my wife.
This gave me the idea—since we usually keep the bedroom windows open at night when it’s that warm—to install some kind of ventilation at the ceiling level and vent it through the roof with a special vent tile. The idea is that warm air rises and, if there’s no wind outside, cool air can still enter the room through the open windows at night. I would handle the controls myself, and theoretically, I could also do the installation.
I would like to hear about pros and cons, experiences, or ideas for implementation here. Perhaps someone else has had the same idea and can share their experience.
PS: I am not interested in heat recovery or similar systems. We live in a rural area connected to a local heating network. I use about 12 MW (megawatts) per year, which is not much, and I pay 4 cents per kW.
This is really just about installing a fan in the roof that I control at night (via my PLC), which exhausts warm air and “pulls in” cooler air through the windows, effectively exchanging the air.
Thanks in advance.
Best regards
I’m new here and will briefly explain the situation before my actual question.
Two years ago, my wife and I built a KFW70 house (timber frame construction) without a basement. The exterior of the house is insulated with wood fiber insulation, and while we don’t have roof windows, the roof tiles are granite gray. Unfortunately, at the time, I didn’t consider ordering additional roof insulation. During very hot summer days, it does get noticeably warm in the bedrooms under the roof (with a high ceiling), which is bearable without a fan but still something I want to address.
Back then, I decided against installing a mechanical ventilation system, which I preferred not to have (the reason is not important here). The windows have a casement opening, and we ventilate regularly (several times a day).
Yesterday was a very warm day (peak outside temperature around 33.9°C (93°F)), and in the bedrooms under the roof, it reached 25.8°C (78°F), which was noticeably uncomfortable for my wife.
This gave me the idea—since we usually keep the bedroom windows open at night when it’s that warm—to install some kind of ventilation at the ceiling level and vent it through the roof with a special vent tile. The idea is that warm air rises and, if there’s no wind outside, cool air can still enter the room through the open windows at night. I would handle the controls myself, and theoretically, I could also do the installation.
I would like to hear about pros and cons, experiences, or ideas for implementation here. Perhaps someone else has had the same idea and can share their experience.
PS: I am not interested in heat recovery or similar systems. We live in a rural area connected to a local heating network. I use about 12 MW (megawatts) per year, which is not much, and I pay 4 cents per kW.
This is really just about installing a fan in the roof that I control at night (via my PLC), which exhausts warm air and “pulls in” cooler air through the windows, effectively exchanging the air.
Thanks in advance.
Best regards
I would install valves in the ceiling and place the fans elsewhere, since any noise, no matter how quiet, can be disturbing when sleeping... and size the fan(s) a bit larger so they can run at half power and be quieter.
The only issue is that in winter the valves need to be tightly sealed, otherwise you could have problems with condensation...
The only issue is that in winter the valves need to be tightly sealed, otherwise you could have problems with condensation...
Hmm.. okay, thanks, I hadn’t thought about that yet. Theoretically, a wall box, also known as Aeroboy (which I installed in the kitchen and am satisfied with), would be the right solution.
I’m reluctant to build an “attic” or similar structure to reduce the noise, but it would be possible...
I’m reluctant to build an “attic” or similar structure to reduce the noise, but it would be possible...
B
Bieber081521 Jun 2017 14:42Boderbär schrieb:
Pros and Cons If I understand correctly, you want to create an opening through the building envelope (in this case, the roof) to install ventilation. The goal is to supply cool night air in a controlled and forced manner (as opposed to an open window).
Poor workmanship could potentially (I’m not familiar with your roof structure) lead to building damage (winter, airtightness, condensation, etc.). So there is a certain amount of effort involved ... Alternative idea: Use a portable air conditioner in the afternoon on hot days to cool the bedroom.
Boderbär schrieb:
Unfortunately, I didn’t think of this back then and ordered the above-roof insulation as well. So the roof isn’t insulated at all? Although then it would be significantly warmer ...
Hello Biber,
thanks for the tips. Yes, you’re right about the lift-and-slide door—it’s not that easy to implement and there is more to consider.
We already have a portable air conditioner; I ran it yesterday as well. But when I see that it’s 15°C (59°F) outside and 23.1°C (73.6°F) in the bedroom, I would still like to continue pursuing the goal with ventilation during the night, even if the heat escapes through the walls and not through the ceiling.
Regards
thanks for the tips. Yes, you’re right about the lift-and-slide door—it’s not that easy to implement and there is more to consider.
We already have a portable air conditioner; I ran it yesterday as well. But when I see that it’s 15°C (59°F) outside and 23.1°C (73.6°F) in the bedroom, I would still like to continue pursuing the goal with ventilation during the night, even if the heat escapes through the walls and not through the ceiling.
Regards
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