ᐅ Inside the house is 10°C warmer than outside – how is that possible?
Created on: 5 Jun 2021 17:44
K
kati1337
Hello!
We are beginners at living in a newly built house, and this first spring is raising some questions.
Our heating system (Tecalor THZ 504) has already decided, based on the outside temperature—which is currently around 20°C (68°F)—that it is in summer mode. In other words, the heating is turned off.
The system information still shows the flow temperature at just under 30°C (86°F), but the flow rate has dropped to zero.
The ventilation is still running, and I suspect our heat recovery unit is causing the issue—because what’s the point of exchanging indoor air with outside air if it blows the air back inside at almost the same warm temperature as it took out?
We only have an outdoor temperature sensor. The device doesn’t handle the indoor temperature very well. It claims the current indoor temperature is 20°C (68°F), but it seems to detect (through measuring) that the exhaust air temperature is about 28°C (82°F). This matches what our various thermometers around the house show.
The question remains: why do we have 28°C (82°F) inside at all? Where is the heat coming from?
Could it be caused solely by sunlight coming through the windows?
We have air conditioning, but I’d rather not run it yet when it’s only about 20°C (68°F) outside and raining.
How do you other new build owners handle this issue? Do you use shading? Something else? Or do you not have this problem at all and maybe there is something wrong with our building services?
We are beginners at living in a newly built house, and this first spring is raising some questions.
Our heating system (Tecalor THZ 504) has already decided, based on the outside temperature—which is currently around 20°C (68°F)—that it is in summer mode. In other words, the heating is turned off.
The system information still shows the flow temperature at just under 30°C (86°F), but the flow rate has dropped to zero.
The ventilation is still running, and I suspect our heat recovery unit is causing the issue—because what’s the point of exchanging indoor air with outside air if it blows the air back inside at almost the same warm temperature as it took out?
We only have an outdoor temperature sensor. The device doesn’t handle the indoor temperature very well. It claims the current indoor temperature is 20°C (68°F), but it seems to detect (through measuring) that the exhaust air temperature is about 28°C (82°F). This matches what our various thermometers around the house show.
The question remains: why do we have 28°C (82°F) inside at all? Where is the heat coming from?
Could it be caused solely by sunlight coming through the windows?
We have air conditioning, but I’d rather not run it yet when it’s only about 20°C (68°F) outside and raining.
How do you other new build owners handle this issue? Do you use shading? Something else? Or do you not have this problem at all and maybe there is something wrong with our building services?
@driver55
You summarized it well. Both policymakers and construction companies (as well as homeowners) primarily focus on energy consumption during the heating season, and everything is geared towards that.
Summer is often neglected. You mostly only read that summer thermal insulation should be considered. But in reality, almost nothing is done. This is due to the mistaken belief that "the insulation will take care of it."
Have you recently (or in the past 10-15 years) walked or driven through newly developed residential areas? That shows what is going wrong. Hardly any houses have shading measures, the trees are not yet grown, but almost every house has large amounts of glass facing south... these buildings are basically greenhouses.
You summarized it well. Both policymakers and construction companies (as well as homeowners) primarily focus on energy consumption during the heating season, and everything is geared towards that.
Summer is often neglected. You mostly only read that summer thermal insulation should be considered. But in reality, almost nothing is done. This is due to the mistaken belief that "the insulation will take care of it."
Have you recently (or in the past 10-15 years) walked or driven through newly developed residential areas? That shows what is going wrong. Hardly any houses have shading measures, the trees are not yet grown, but almost every house has large amounts of glass facing south... these buildings are basically greenhouses.
Mycraft schrieb:
Shading measures What do you consider to be effective shading solutions?
In my opinion, at least Venetian blinds on the ground floor south and west sides, plus a roof overhang of at least 1 meter (3 feet) for the upper floor.
kati1337 schrieb:
Outdoor temperature – currently about 20°C (68°F) – it has long been decided that it’s summer mode. In other words, the heating is off.
The system info still shows a flow temperature just under 30°C (86°F), but the volume flow has dropped to zero. Outside 20 degrees and inside 30 degrees? How about manually ventilating for half an hour? I’d think even in a new build it should be possible to open all windows, right? 😉
Schimi17916 Jun 2021 16:51hampshire schrieb:
Take a Tupperware container, put a thermometer inside, close it, and place it in the sun.
…Why make it so ‘complicated’? 😀
In my opinion, good insulation isn’t necessary. Just sit in a car without air conditioning on a sunny day or drive it.
Greenhouse effect?
KingJulien schrieb:
You can install the cassette yourself, it’s no problem. Why would the heat exchanger be damaged if it’s stored in a box instead of inside the heating system? As long as no pets or children mess with it 😉 We have pets and a child at a curious age, so I’m a bit worried. 😀 Maybe store it in the attic. But it gets very hot up there in summer.
KingJulien schrieb:
Regarding the bypass, the question is whether one is installed or not. Since you have a compact unit, maybe there isn’t one. We have the THZ 504, which is probably identical to the Stiebel Eltron 504. Unfortunately, I don’t know if there’s a bypass installed; I’ll try to check and see if I can make sense of the technical terms. In the menu there’s both a "summer cassette" and a "bypass" setting. Doesn’t it make sense to have only one of those?
KingJulien schrieb:
As far as I know, Tecalor is the no-name brand of Stiebel Eltron. That’s why the menu navigation is quite similar to ours. Yes, not exactly “no-name,” but I believe SE only allows certain installers, or something like that. Anyway, their technician was at our house during commissioning, and when we asked if the unit was comparable to the SE 504, he said something like, “Comparable? It’s exactly the same, just with a different label.”
KingJulien schrieb:
Regarding summer operation, I would check the values again. Right now, it’s too warm inside. But if you reach a comfortable indoor temperature, it might be that the heating comes on during a cold night, even if it’s 30 degrees during the day. What do you mean by that? I’m still experimenting with how to keep the indoor temperature comfortable during the day. If I don’t change anything with the system, the indoor temperature shouldn’t change as long as the heat exchanger is off—“no heat lost.” I’ve already asked our plumber about this.
hampshire schrieb:
- Prevent heat from entering the house. There are three measures: avoid direct sunlight through windows by shading, do not let hot air in by keeping openings closed, and turn off the heating.
- Provide active cooling
Thanks. We’ll try shading in the next few days and get used to it.
Not letting hot air in probably means turning off the ventilation during the day in summer.
At the moment, that’s not really our problem because it’s still cooler outside than I want it inside. Our problem is that it’s 20°C (68°F) outside but 28°C (82°F) inside.
What I don’t quite understand is where the warm air keeps coming from. Yesterday we ran the air conditioning for the first time—it works, of course—but we had planned to use the AC only in summer, not from the first sunny day. Last night sleeping was comfortable, but this morning the bedroom was already a sauna again. Where is it coming from? Are we radiating that much heat? It wasn’t an issue in winter. The sun hasn’t shined at all yesterday or today. Where is the heat coming from? O.o
Schimi1791 schrieb:
That’s why I praise electric shutters (or similar) with sun sensors. They close about 80%, blocking most of the heat but still letting in enough light. We didn’t consider that back then—I’d build differently today.
driver55 schrieb:
Where is the house located? Something doesn’t quite add up. For some, the heating was still running until two weeks ago (also new builds with ventilation systems), but you already have 28 degrees inside. What kind of “high-tech houses” do you have? The house is in northern Germany. It’s cool and rainy outside. It’s built to KFW55 standard. That’s why I’m wondering if something is off here or where the heat is coming from.
driver55 schrieb:
Exactly, new builds should have everything planned. Usually, only “winter” (heating) is considered, while “summer” (shading/cooling) is ignored. That’s true. It wasn’t really discussed with the builder beforehand. I’m glad my husband insisted on having air conditioning. But airtightness is really only considered for winter. For summer, they think, “I’ll just keep hot air out and keep the house cool”—but it doesn’t work that way.
T_im_Norden schrieb:
@kati1337
Try turning on passive cooling. Which setting would you recommend? I can select between “Off,” “Supply air,” “Extract air,” “Bypass,” and “Summer cassette.”
DaSch17 schrieb:
20 degrees outside and 30 inside? How about manually ventilating for half an hour? Even in a new build, you should be able to open all the windows, right? 😉 Possible, yes; desirable, no. 😀
To open all windows, I’d first need insect screens. I only have a few installed so far. But I’d rather have the heat inside than bugs.
Actually, I don’t want either inside, but bugs are worse.
I think we really have to tackle this more seriously. But there must be a way to bypass the heat recovery on the ventilation system for summer. We will probably need to buy a summer cassette.
In the THZ 504, passive cooling is activated through ventilation. Further information MUST be provided to you by the plumber. However, make sure to have your system explained to you as thoroughly as possible and try to understand all the functions. Take detailed notes during this process.
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