ᐅ Newly built apartment (KfW-55 standard) cannot be cooled below at least 25 °C.
Created on: 21 Aug 2022 08:52
F
Forsberg21
Hello,
I have rented out a new apartment (built in 2021, KfW-55 standard). The tenant recently informed me that since spring, the indoor temperatures have consistently been at least 25°C (77°F) or higher. On warm days, it even reaches up to 28°C (82°F), although she keeps all the aluminum shutters closed during the day (no home office). Cross-ventilation at night doesn’t bring the temperature below 25°C (77°F). She is asking for advice on how to cool the apartment down a bit during the summer.
What could be causing this?
The apartment has a decentralized ventilation system and underfloor heating, which is naturally turned off in summer.
The apartment faces southwest and has large window areas.
Could it be that the ventilation system continuously brings in warm outside air on hot days, causing the temperature to rise so much?
Should the ventilation system be turned off during the day?
But why doesn’t the apartment cool down at night, even though there seems to be cross-ventilation and the nights are cooler?
Do you have any tips? I am a bit overwhelmed.
Best regards,
Robert
I have rented out a new apartment (built in 2021, KfW-55 standard). The tenant recently informed me that since spring, the indoor temperatures have consistently been at least 25°C (77°F) or higher. On warm days, it even reaches up to 28°C (82°F), although she keeps all the aluminum shutters closed during the day (no home office). Cross-ventilation at night doesn’t bring the temperature below 25°C (77°F). She is asking for advice on how to cool the apartment down a bit during the summer.
What could be causing this?
The apartment has a decentralized ventilation system and underfloor heating, which is naturally turned off in summer.
The apartment faces southwest and has large window areas.
Could it be that the ventilation system continuously brings in warm outside air on hot days, causing the temperature to rise so much?
Should the ventilation system be turned off during the day?
But why doesn’t the apartment cool down at night, even though there seems to be cross-ventilation and the nights are cooler?
Do you have any tips? I am a bit overwhelmed.
Best regards,
Robert
motorradsilke schrieb:
Can’t you cross-ventilate the bedroom in the evenings and at night through other rooms?
We have a KfW55 energy-efficient house, but we have absolutely no problems.
During the day, several windows and doors are open here; when it’s 30°C (86°F) outside, it’s that warm inside as well. I don’t mind—on days like that, I’m usually outside anyway.
In the evenings, there’s a through-draft in the whole house, which quickly cools down the heat. It usually gets to a comfortable 25 to 26°C (77 to 79°F).
Only the bedroom with a west-facing window (though the sun only reaches it late in the day) is shaded with roller shutters during the daytime. In the evening, we open the window, leave it open overnight, and lower the shutter, but keep about 20cm (8 inches) of space open at the bottom. That way we can sleep very well. The bedroom temperature in the evening is usually a maximum of 24°C (75°F), and in the morning often only 21 to 22°C (70 to 72°F).
In my opinion, ventilation at night is the most important thing. motorradsilke schrieb:
Your husband is worried about burglary risk because of the windows on the upper floor? Where do you live exactly? Somewhere that’s bright at night and you need soundproof windows? That’s unfortunate but probably not typical for detached houses.
By the way, we have a bungalow, so the bedrooms have ground floor windows. That’s why we lower the roller shutter about 20cm (8 inches) and open the window. Burglars don’t want to get caught, so they almost certainly wouldn’t break into an occupied bedroom. That only happens in crime dramas. We live in the countryside, in a new residential area with about 20 houses at the end of a cul-de-sac. If you want to sleep later than 7 a.m. on a Saturday, it’s better to keep the windows closed. There’s kids playing noise, neighbours working, cutting tiles, paving, woodworking, lawn mowing, and so on… And lawn mowing plus kids riding around on toy cars will continue for some time. It’s already light outside at that time in the morning.
We don’t have roller shutters but shutters on the windows instead—they can be closed, and some air still gets through. But even that he doesn’t dare to leave open on the ground floor because we usually sleep upstairs. If someone tries to break in there, we wouldn’t notice at all.
Maybe not your bedroom, but what if you leave the other side of the house open for cross-ventilation?
M
motorradsilke21 Aug 2022 17:05Snowy36 schrieb:
We live in a rural area, in a new development with about 20 houses at the end. If you want to sleep in past 7 a.m. on a Saturday, it’s better to close the windows. Kids making noise, neighbors working on projects, cutting tiles, paving, chopping wood, mowing the lawn, and so on… And mowing and kids playing on ride-on toys will continue. It’s already bright by that time in the morning.
We don’t have roller shutters but window shutters, which you can close. That lets some air in, but not much. Still, he doesn’t dare leave them open on the ground floor… Because we actually sleep upstairs; if someone were to make a noise there, we wouldn’t notice.
Maybe not in your bedroom, but what if you have cross-ventilation open on the other side of the house? I don’t keep cross-ventilation going through the night, only until I go to bed, which is enough.
Then I just leave the bedroom window open.
I guess everyone has to find their own way.
During the day, we darken the rooms with roller shutters (at least on the south/west side), ventilate thoroughly in the morning and evening by opening windows completely on opposite sides, and keep all windows slightly open (tilted) at night on the upper floor.
In summer, the temperature was always around 23-24°C (73-75°F). The maximum on the upper floor was about 25°C (77°F) during days over 30°C (86°F) when the temperature in the evening also stayed above 20°C (68°F), so the house didn’t cool down much overnight.
In summer, the temperature was always around 23-24°C (73-75°F). The maximum on the upper floor was about 25°C (77°F) during days over 30°C (86°F) when the temperature in the evening also stayed above 20°C (68°F), so the house didn’t cool down much overnight.
motorradsilke schrieb:
Burglars do not want to get caught; they most likely won’t break into an occupied bedroom.They also break into new housing developments less often (in fact, hardly at all) because they know there is nothing worth stealing there. (Exception: luxury homes)driver55 schrieb:
They also break in less often (or not at all) in new housing developments because they know there’s nothing worth stealing there. (Exception: villas) Where do you get that information from, are you a burglar?
In our area, burglaries are currently happening in new housing developments because they are conveniently located near the B16 road, making it easy to quickly get to the Czech Republic.
W
WilderSueden22 Aug 2022 09:08I see two issues here:
1. A southwest orientation is not ideal because you get the afternoon sun. Once the balcony heats up, ventilating will mainly transfer the heat into the house.
2. Even if all windows are open, a proper cross breeze is unlikely since the air has to travel around multiple corners. This only works well if there is a strong wind. It is especially problematic in the bedrooms because—as is typical in apartment buildings—there is usually only one window, so the air has to flow through the entire apartment.
There is only limited potential to address both issues.
1. A southwest orientation is not ideal because you get the afternoon sun. Once the balcony heats up, ventilating will mainly transfer the heat into the house.
2. Even if all windows are open, a proper cross breeze is unlikely since the air has to travel around multiple corners. This only works well if there is a strong wind. It is especially problematic in the bedrooms because—as is typical in apartment buildings—there is usually only one window, so the air has to flow through the entire apartment.
There is only limited potential to address both issues.
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