Newly built apartment (KfW-55) cannot be cooled, always at least 25 °

I am surprised that on the previous four pages no one has considered the waste heat generated. Cooktop, oven, refrigerator, washing machine, dryer, dishwasher, vacuum cleaner, large flat-screen TV, computer (with house construction forum) and of course the human body all produce waste heat, and in a four-person household this can reach quite significant levels. When it is warmer outside than inside, the waste heat has no chance to escape. Alone this can cause the indoor temperature in a well-insulated house to rise by a few degrees. The only counteracting factor is the heat capacity of the building structure. But even that has its limits, as has already correctly mentioned.

Yes, almost everyone is surprised at how poorly a new building insulates against heat.

That may be the general observation, but it has nothing to do with physics. Thermal insulation of course always works in both directions.

So the heat either comes in from outside or is generated inside and cannot get out. Those are the two relevant drivers. Against the one, external shading and good glazing help; against the other, a change in one’s own behavior. But we all know how hard it is to change one’s own behavior. ;)

Finally, a thread that really concerns me again .... What are the buildings being discussed here made of? Do you think the material makes a difference? We have a KFW 55 house monolithic, the relatives have a KFW55 lime sand with insulation and a KFW40 wooden house. In our house, I almost died in the summer. 26 degrees on the ground floor that wouldn’t go away. Even yesterday at 17 degrees outside I ventilated all day and today it’s 23.5 again, which I can of course live with, but it’s crazy how quickly it goes up again. The worst is the bedroom (east side) because we can’t get any airflow in when the window is open. I always thought that living quality in new builds is higher than in old buildings, but no way. Well, at the current prices I will be happy about saved heating costs, but in general I would rather have heated a bit more in winter than now having to install an air conditioning plus photovoltaic system for the corresponding price so that I don’t die. Home office at 26 degrees is somehow not my thing.

With the KFW40 wooden house I had the impression that the 24 degrees there felt a bit fresher even though we have ventilation and they don’t.

We have been sleeping in the basement the last few weeks, which is super but also somehow annoys me. Expensive house, expensive bed and I sleep in the basement on the guest bed, great.

To the OP: definitely reprogram the ventilation, it must not let the warm air in during the day! But at night it shouldn’t let the cool air back in through the heat recovery either, so cool without going through the exchanger. That doesn’t cool, but prevents additional heating.

The apartment is equipped with a decentralized residential ventilation system

With heat recovery? If so, do not turn it off during the day. Because if it is warmer outside than inside, the controlled residential ventilation cools rather (the heat stays on the warm side – just the opposite of summer). And at night – depending on the settings – set some units to supply air and others to exhaust air.

It is a building with 36.5 cm thick brick exterior walls (thermal insulation bricks with thermal insulation mortar). No additional insulation is applied.

I do not understand this sentence: "Dafür soll sie nachts dann die kühle Luft nicht über die Wärmerückgewinnung wieder reinlassen also kühl ohne das sie über den Tauscher läuft . Das kühlt zwar nicht aber verhindert zusätzliches aufheizen."

The ventilation settings only include exhaust air mode (heat recovery deactivated), supply air mode (heat recovery deactivated), and regeneration mode (switches every 70 seconds between exhaust air and supply air mode, heat recovery active).

With heat recovery? If yes, then do not turn it off during the day. Because if it is warmer outside than inside, the controlled residential ventilation rather cools (the heat stays on the warm side - just the opposite of summer). And at night - depending on the settings - set some devices to supply air and others to exhaust air.

Yes, with heat recovery. Unfortunately, there is only one central switch and you can only set all 5 fans to supply air, exhaust air, or regeneration mode. And now I am really a bit confused because the ventilation system should now still be kept on.....

Finally, a thread that really concerns me again... What are the buildings being discussed here made of? Do you think the material makes a difference? We have a KfW 55 house monolithic, the relatives have KfW55 sand-lime brick with insulation and KfW40 wooden house. In our house, I almost died in summer. 26 degrees in the ground floor that couldn't be gotten rid of. Even yesterday at 17 degrees outside I ventilated all day and today it's 23.5 again, which I can of course live with, but it's crazy how fast it goes up again. The worst for us is the bedroom (east side) because we don't get any airflow in when the window is open. I always thought new buildings have a higher quality of life than old buildings, nope. Well, at the current prices I will still be happy about saved heating costs, but in general I would rather have heated a bit more in winter than have to install an air conditioner plus photovoltaics here for the corresponding price so I don't die. Home office at 26 degrees is somehow not my thing.

With the KfW 40 wooden house, I had the impression that the 24 degrees there felt a bit fresher even though we have ventilation and they don't.

We have been sleeping in the basement the last few weeks, which is great but somehow annoys me too. Expensive hut, expensive bed and I sleep in the basement on the guest bed, great.

To the OP: definitely reprogram the ventilation, it must not let warm air in during the day! At night it should then not let the cool air back in through the heat recovery, so cool without running through the exchanger. That doesn't cool but prevents additional heating.

Can't you ventilate crosswise in the bedroom with other rooms in the evening and at night?

We have a KfW55 house but have absolutely no problems. During the day, several windows and doors are open, if it's 30 degrees outside, I have that in the house too. I don't care, in this weather I'm only outside anyway. In the evening there is a draft through the whole house, the heat goes out quickly, usually it gets to a pleasant 25 to 26 degrees. Only the bedroom with west-facing window (however, the sun only hits it late) we shade with blinds during the day. Then in the evening the window is opened, overnight the window is kept open and the blind is down, leaving about 20 cm open at the bottom. That way we can sleep well, in the bedroom it's a max of 24 degrees in the evening, usually only 21 to 22 degrees in the morning. From my point of view, ventilating at night is the most important thing.