ᐅ Newly built apartment (KfW-55 standard) cannot be cooled below at least 25 °C.
Created on: 21 Aug 2022 08:52
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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
S
SaniererNRW12321 Aug 2022 12:59Forsberg21 schrieb:
And now I’m really a bit confused because you’re supposed to keep the mechanical ventilation running..... No need to be confused. At night, the controlled mechanical ventilation does what it’s supposed to do (in regeneration mode). So, like in winter, the “cold” air stays outside and the warm air stays inside. During the day, this changes because it’s warmer outside than inside. The function of the ventilation system itself doesn’t change, but this time it keeps the warmth outside and lets the cooler air into the house.
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Forsberg2121 Aug 2022 13:08SaniererNRW123 schrieb:
Don't be confused. At night, the controlled residential ventilation system does what it’s supposed to do (in regeneration mode). So, like in winter, the "cold" air stays outside and the warm air stays inside. During the day, it changes because it’s warmer outside than inside. The function of the controlled residential ventilation system doesn't change, but this time it keeps the outside warm and lets the cooler air into the house. Okay, got it. However, my tenant seems to be airing crosswise at night, so the controlled residential ventilation system probably has no effect anymore because some windows are open. But if the windows remain closed at night, what would be the best setting for the controlled residential ventilation system? Regeneration mode not recommended, since then the cold air stays outside. Probably best to keep it permanently on supply air mode, because then cold air is drawn in. However, heat recovery is disabled in this mode. The problem could be that other issues might arise with continuous supply air operation...
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Interrupt21 Aug 2022 13:17Night ventilation is probably the best advice you can give and should work well in a single-family house. But what about in a rental apartment?
I know of cases where, in winter, an apartment requires only minimal heating because the neighbors above and below already heat well, and the warmth spreads across the apartments. In summer, it should actually be the same, so that all residents in the building would need to cross-ventilate their apartments for this to have a noticeable effect. Otherwise, the building will not cool down significantly overnight.
I know of cases where, in winter, an apartment requires only minimal heating because the neighbors above and below already heat well, and the warmth spreads across the apartments. In summer, it should actually be the same, so that all residents in the building would need to cross-ventilate their apartments for this to have a noticeable effect. Otherwise, the building will not cool down significantly overnight.
@motorradsilke
Well, I’m building a bunker here with soundproof windows and so on. And then leaving the window open at night?! Also, the room is bright, so I can’t sleep…. That’s why I moved to the basement… but it’s reassuring to hear that you do it like that and it’s apparently normal…
Cross-ventilation would be possible with the rooms on the west side, but all the windows there are floor-to-ceiling, and my husband is afraid to leave them open because of the risk of burglary.
And on the ground floor, for the same reason, you can’t leave anything open at night, and when I get up at 8, it’s already too warm again. Sometimes I even got up at 5 just to ventilate for half an hour, but I stopped doing that because after 30 minutes the temperature was back to where it was before anyway.
Well, I’m building a bunker here with soundproof windows and so on. And then leaving the window open at night?! Also, the room is bright, so I can’t sleep…. That’s why I moved to the basement… but it’s reassuring to hear that you do it like that and it’s apparently normal…
Cross-ventilation would be possible with the rooms on the west side, but all the windows there are floor-to-ceiling, and my husband is afraid to leave them open because of the risk of burglary.
And on the ground floor, for the same reason, you can’t leave anything open at night, and when I get up at 8, it’s already too warm again. Sometimes I even got up at 5 just to ventilate for half an hour, but I stopped doing that because after 30 minutes the temperature was back to where it was before anyway.
KingJulien21 Aug 2022 14:20As a temporary measure, I’m also adding a fan. I know, it’s a bit old-fashioned. But it really helps with the perceived temperature.
Apart from that, 25 degrees Celsius (77°F) indoors in this weather isn’t much; it’s quite normal.
Apart from that, 25 degrees Celsius (77°F) indoors in this weather isn’t much; it’s quite normal.
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motorradsilke21 Aug 2022 14:31Snowy36 schrieb:
@motorradsilke
Well, I’m basically building a bunker with soundproof windows, etc. And then I leave the window open in the evening?! Plus, the room gets bright, so I can’t sleep…. That’s why I moved to the basement… but it’s reassuring to hear that you do the same and that it’s probably normal…
Cross-ventilation would be possible with the rooms on the west side, but all their windows are floor-to-ceiling, and my husband is afraid to leave them open because of burglary risk. And on the ground floor, for the same reason, nothing can be left open at night. If I wake up at 8, it’s already too warm again, or sometimes I’ve gotten up at 5 to ventilate for half an hour, but I stopped doing that because after 30 minutes the temperature was back to where it was before anyway.Is your husband really afraid of break-ins through the windows upstairs? Where do you live? In a place where it’s also bright at night and you need soundproof windows at night? That is obviously unfortunate, but it’s probably not the usual case for detached houses.By the way, we have a bungalow, so the bedroom windows are on the ground floor as well. That’s why we have shutters lowered to about 20cm (8 inches) and keep the window open. Burglars don’t want to get caught; they almost certainly won’t try to break into an occupied bedroom. That only happens in crime novels.
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