ᐅ Ventilation system during warm summer conditions

Hello everyone,

We have been living in our new home with a central ventilation system for just over a year now and are very satisfied so far.

The only issue is the temperature in the attic bedroom (north-east side) in the evening, which is not very comfortable. The room is not even facing south, yet the temperature reaches about 23°C (73°F) in the evening, even though we open the windows wide in the morning to ventilate with cool air and then close the curtains completely.

I suspect that the ventilation system continuously blows warm air from outside (logically) into the bedroom, causing the warm air to accumulate there.

How do you handle this? Is there anything specific to consider?

My ventilation system has been running at level 2 for several months now because I felt the air in the room was fresher, especially during winter. Maybe I could lower it again during summer?

Is there anything else that can be adjusted to improve the situation? Or is the only option to open everything wide for half an hour before going to bed to ventilate again?

I appreciate any advice, tips, or tricks.

With active heat recovery, the heat gain through a central controlled residential ventilation system is very low.
The people sleeping there generate significantly more heat.

RotorMotor schrieb:

With active heat recovery, the heat input from a central controlled residential ventilation system is very low.
The people sleeping there produce significantly more heat.

My main concern is that the ventilation system continuously supplies warm air to the room—instead of (without ventilation) airing out in the morning and evening when temperatures are cooler. If you then keep everything darkened, hardly any heat should enter the room without ventilation, right?

But with ventilation, I don’t really have a choice, correct?

Or are there any special settings that can be adjusted here?

Possibly through the bypass function?

No difference – I had the same issue with my wife last year during the heatwave. We turned off the ventilation for three days. The temperature inside the house was the same, but we felt uncomfortable due to the lack of airflow.

Around the time of the heatwave, we had 27°C (81°F) indoors in a KfW 55 standard house. I asked a family living in a KfW 40 house: they had 28°C (82°F) inside. Another family with a house from 1990 reported 23°C (73°F) indoors. I believe new houses no longer let heat escape. It was often the case that at 5 p.m. we still had 25°C (77°F) inside and thought “great, today it won’t reach 27°C (81°F).” Then you notice how the brick absorbs and radiates solar heat both inside and outside—it really radiates. Before you know it, it’s 27°C (81°F) again. Fortunately, we’ve had an air conditioning system in the living-dining area for about a month now, including BAFA support (which expired in 2023—I applied in 2022).

Best regards

Prager91 schrieb:

What I’m really concerned about is that the ventilation system continuously brings warm air into the room

From a heating capacity perspective, that’s really negligible.
I have calculated this a few times before.
I can look it up again if needed.

Or calculate it for you. What airflow rate is the system set to?
How warm is it inside and how warm is it outside?

Prager91 schrieb:

If you darken everything, then (without ventilation) no significant heat should enter the room, right?

That would mean your house is so well insulated that you wouldn’t need heating at all in winter if you didn’t ventilate.
But that’s not the case.
“Heat” passes through the building envelope just like “cold” does.
Maybe even more so, because the sun heats up the building components, which then release that heat inside.

And, as I said, people produce much more heat than a ventilation system.