ᐅ House (built in 2019) always too warm from April to October

Hello everyone, I wasn’t sure under which category to post this topic.

We have been living in our house for about four years now; it was built in 2019. The house is built into a slope, with the ground floor containing the living area, kitchen, workspace, and a small bathroom, and the basement level having the bedrooms, building services, and utility room. The attic is not converted.

Now that it’s slowly getting warmer, I notice again, as I do every year:
It’s so warm inside the house. The heating system, underfloor heating (heat pump), is no longer running. We have a thermometer in the cloakroom on the ground floor. This morning it showed 23.4°C (74°F), stuffy and uncomfortable.

Our house has a ventilation system (Wolf), a central ventilation unit. It runs at night and is supposed to bring fresh air into the house or extract air from the rooms as needed.

How can it be that we always have such heat? 23.4°C (74°F) in the hallway?

Of course, I should mention that we get a lot of sun. On the ground floor, in the living area, there are large south-facing windows which we shade when the sun is shining.
In the basement, the terrace door is 2m (6.6 ft) wide and also exposed to the sun. We shade that partially.

We installed the ventilation system back then because it was said to save us from having to open all the windows every morning. Now, between April and October, I basically spend my mornings opening all the windows anyway to get rid of the stuffy and unpleasant warmth inside the house.

Does anyone have similar experiences? How can it be that after a night with 12°C (54°F) outside temperature, the hallway is 23.4°C (74°F) at 7 a.m.?

When I leave the bedroom and walk up the stairs to the ground floor, I can feel the temperature rising with every step :-/

Could this be related to the building services system? The house was built in 2019, with 36cm (14 inch) Porit bricks.

Thanks for your help, best regards
ina

chewbacca123 schrieb:

Of course, I have to mention that we get a lot of sun.

That already gives you part of the answer.
We had similar issues in our 2020 KFW55 house. At some point in May, it reached 28°C (82°F) inside, even though outside temperatures were quite mild.
The problem is that the houses are airtight, and all the heat generated inside is retained – which is the whole point of their design. Unfortunately, this also applies during summer.

For us, it was also because we had a heat recovery ventilation system that didn’t come with a factory-installed bypass. Do you have an automatic bypass that switches off the heat recovery function above a certain temperature? Our new ventilation system has that.

People often underestimate how much large window areas heat up the house. Our plumber once calculated it for us, but unfortunately, I’ve forgotten the figures. Basically, on sunny days, you’d need to turn your home into a hobbit hole to avoid overheating.

By how much does the temperature drop overnight?
What material do you use for intermediate ceilings? Once concrete has heated up, ventilating for half an hour is not enough.

Hello,

chewbacca123 schrieb:

The terrace door in the basement, 2 m (6.6 ft) wide, is also exposed to the sun. We are shading it halfway.

There you have it... Roughly estimate about 1 kW heating power per square meter of window (this isn’t exact, since the sun doesn’t always hit it perfectly vertically, but it’s in that range). So if you partially shade a 2 by 2 m (6.6 by 6.6 ft) terrace door, you’re still bringing roughly 2 kW of solar heat into the house. That’s like running two electric fan heaters during the day in your living room!

Best regards,

Andreas

andimann schrieb:

Hello,

WilderSueden schrieb:

How much does the temperature drop overnight?
What material do you have for the intermediate ceilings? Once concrete has warmed up, airing out for just half an hour isn’t enough.

First of all, thank you for your answers.

andimann schrieb:

Hello,

There you have it... Roughly estimate about 1 kW heating power per square meter of window (this isn’t exact because the sun isn’t perfectly perpendicular, but it’s in the ballpark). If you partially shade a 2 by 2 meter (6.5 by 6.5 feet) patio door, you’re still bringing about 2 kW of heating power into the house. That’s like having two fan heaters running in your living room during the day!

Best regards,
Andreas

Thank you for your responses. Our house definitely gets quite a bit of sun, that’s true. We’ve also retrofitted an air conditioning system for the entire living area, which includes living, dining, and kitchen – a 55 m² (590 sq ft) open space. It’s absolutely invaluable!

Regarding heat recovery, according to our heating engineer, we have a bypass. Still, I feel like it might not be working properly? I plan to have it checked again when I get the chance.

This morning, when I went upstairs to the hallway, it was 23.4°C (74°F) there. After opening the shutters and windows, the temperature dropped to 22.2°C (72°F). In the living area, it was 23.2°C (74°F), now 21.4°C (70°F) with the windows tilted open. Outside it’s 16°C (61°F). This suggests to me that the indoor temperature hardly decreases overnight.

In summer, we run the ventilation system only from 11:00 pm to 5:00 am. Otherwise, warmer air gets pulled into the house during the day. Currently, it’s still running during the daytime as the weather isn’t very warm yet.

It would probably help to shade the patio door, which already has glass overhead, without keeping the shutters completely closed—otherwise you can’t go in or out. That’s just inconvenient.

The heat inside the house is really bothersome and frustrating. You think you’re building your dream home, but after the first summer I wondered, what is this? Sometimes it was more comfortable in our old attic apartment… I find that very disappointing and would really like to find a solution somehow. When I visit other houses, I don’t get the feeling it’s as stuffy as it is here, even though those are also newly built homes.

chewbacca123 schrieb:


Regarding the heat recovery system, according to the heating engineer, we have a bypass. Still, I feel like it might not be working properly? I plan to have it checked again when I get the chance.

It doesn’t have to be that way. The bypass doesn’t cool directly; it only prevents additional heat from being retained inside the house. But the heat gain that andimann describes through the veranda door can’t be stopped by the bypass.
We also built our house with air conditioning. The only other way to avoid excessive heating is to be very consistent with shading. However, I find that a bit oppressive, having to darken every possible opening for three seasons. After all, that’s not why we installed huge windows. =)