ᐅ Design of Underfloor Heating for a KfW 55 Energy-Efficient House with a Ventilation System
Created on: 17 Feb 2023 16:29
D
dream2023
Dear users,
I am a bit overwhelmed with whether our underfloor heating is being planned correctly. The house is still in the shell stage. I have requested the installation plans and heat load calculations from the general contractor. The heat load was calculated according to DIN EN 12831. I have this calculation and the results from the planning office.
The pipe spacing is mostly 18cm (7 inches), except in the bathrooms (once 6cm (2.5 inches), once 12cm (5 inches)) and the utility room (24cm (9.5 inches)). What unsettles me more is the fact that in both bathrooms an undercoverage of the heat load is stated ("missing heat ...kW"). Additional heating devices are not planned there so far.
May I post the planning documents if I redact personal information and the data of the planning office?
Best regards
I am a bit overwhelmed with whether our underfloor heating is being planned correctly. The house is still in the shell stage. I have requested the installation plans and heat load calculations from the general contractor. The heat load was calculated according to DIN EN 12831. I have this calculation and the results from the planning office.
The pipe spacing is mostly 18cm (7 inches), except in the bathrooms (once 6cm (2.5 inches), once 12cm (5 inches)) and the utility room (24cm (9.5 inches)). What unsettles me more is the fact that in both bathrooms an undercoverage of the heat load is stated ("missing heat ...kW"). Additional heating devices are not planned there so far.
May I post the planning documents if I redact personal information and the data of the planning office?
Best regards
D
dream202320 Feb 2023 16:37If I understand the trends here correctly, then (taking, for example, the upper floor) smaller pipe spacing would probably lead to two heating circuits in each bedroom, right? Otherwise, the pipes would be too long?
Right, the lengths shouldn’t be too long; you need to check what the heating engineer is willing to do. Definitely keep them under 100 meters (328 feet).
For example, in the living room we have 4 loops, arranged more tightly in front of the window, and omitted under the kitchen cabinets/island.
For example, in the living room we have 4 loops, arranged more tightly in front of the window, and omitted under the kitchen cabinets/island.
A
Allthewayup20 Feb 2023 18:19Pacmansh schrieb:
That’s right, the lengths shouldn’t be too long—you have to see what the heating engineer is willing to do. Definitely keep it under 100 meters (330 feet).
For example, in our living room, we have four circuits, arranged tighter in front of the window, and omitted under the kitchen cabinets/island. The discussion about leaving out heating loops under kitchen cabinets is a whole topic on its own. If the kitchen is located along an external wall, most general contractors won’t agree to it because they worry it could get too cold there, causing condensation in the room air and leading to mold risk. Another aspect is that if the island is removed in 20 years, you’ll have a cold spot. We are still facing this decision ourselves and will probably have the island heated but not under the kitchen counter since it is on an internal wall.
When we built in 2014, the general contractor installed a heating system designed for 20cm (8 inches) radiators with a 45°C (113°F) supply temperature. That seemed a bit high to me, especially considering the gradually increasing demand and market readiness for heat pumps. So, for about 1000€ we had it redesigned for 10cm (4 inches) radiators with a supply temperature of around 35°C (95°F).
For several years now, my boiler’s heating curve has been set to -5°C (23°F) → 32°C (90°F) supply temperature, 0°C (32°F) → 30°C (86°F) supply temperature, and +7°C (45°F) → 28°C (82°F) supply temperature. The house is always comfortably warm at 21+°C (70+°F) — my wife even walks around the house in light clothing during winter :p.
What I want to say is, even when designing for 35°C (95°F), you can comfortably lower the supply temperature further and the house still stays warm.
For several years now, my boiler’s heating curve has been set to -5°C (23°F) → 32°C (90°F) supply temperature, 0°C (32°F) → 30°C (86°F) supply temperature, and +7°C (45°F) → 28°C (82°F) supply temperature. The house is always comfortably warm at 21+°C (70+°F) — my wife even walks around the house in light clothing during winter :p.
What I want to say is, even when designing for 35°C (95°F), you can comfortably lower the supply temperature further and the house still stays warm.
D
dream202321 Feb 2023 08:17Hello,
I just spoke with the heating engineer. I would say it was a good conversation. We are increasing the temperature to 22°C (72°F) in all living and bedrooms.
He is not using the air bubble mat at all; instead, he is stapling, so we are not completely fixed on that. He would actually prefer not to have two heating circuits upstairs in the bedroom because, first, the manifold would need to be enlarged, and second, he believes he can manage well with a maximum of 120 meters (394 feet) per pipe. Downstairs, he still has space for more heating circuits, at least for now. We have now agreed on maximum pipe spacing of 15 cm (6 inches). I am fine with that. In the bathrooms, because of the reduced floor covering thickness, he can still make some adjustments; he is only using the calculation as a guideline there.
We will have to partially cover the cost of the pipes ourselves. Otherwise, he can't stay within the general contractor’s budget cap. I am now satisfied that he was so open to making adjustments.
One more question: are we still eligible for the KfW funding? There shouldn’t be any problems with the change to the pipe spacing, right? As far as I understand, that shouldn’t be an issue.
I just spoke with the heating engineer. I would say it was a good conversation. We are increasing the temperature to 22°C (72°F) in all living and bedrooms.
He is not using the air bubble mat at all; instead, he is stapling, so we are not completely fixed on that. He would actually prefer not to have two heating circuits upstairs in the bedroom because, first, the manifold would need to be enlarged, and second, he believes he can manage well with a maximum of 120 meters (394 feet) per pipe. Downstairs, he still has space for more heating circuits, at least for now. We have now agreed on maximum pipe spacing of 15 cm (6 inches). I am fine with that. In the bathrooms, because of the reduced floor covering thickness, he can still make some adjustments; he is only using the calculation as a guideline there.
We will have to partially cover the cost of the pipes ourselves. Otherwise, he can't stay within the general contractor’s budget cap. I am now satisfied that he was so open to making adjustments.
One more question: are we still eligible for the KfW funding? There shouldn’t be any problems with the change to the pipe spacing, right? As far as I understand, that shouldn’t be an issue.
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