ᐅ Lowering the Supply Temperature in Underfloor Heating Systems More Complex Than Expected?
Created on: 9 Mar 2023 22:07
J
JohnnyEH
Hello everyone!
We are currently discussing the supply temperature for the underfloor heating system with our prefab house provider.
The house is a timber frame panel construction and meets the KFW40 standard.
According to the construction description, the provider sets the supply temperature of the underfloor heating to 35°C (95°F). We mentioned that we consider this outdated for a new build and would prefer a supply temperature of around 30°C (86°F). We were then told that with a supply temperature of 30°C (86°F), a larger heat pump and a completely different heating system design would be required, and the additional costs could quickly reach five figures. Such extra costs obviously would not make financial sense.
Until now, I thought the supply temperature was primarily determined by the pipe spacing and would be lower if the pipe spacing was reduced.
Why could a lower supply temperature lead to a larger heat pump? What am I missing?
I should add that the heating load calculation and the exact determination of the heat pump have yet to be done. In any case, a Vaillant Arotherm Plus will be used.
Additionally, a question about the floor covering.
We know that tiles are optimal for underfloor heating but vinyl is almost equivalent. We will also have an active underfloor cooling system installed (via the air-to-water heat pump). Does either floor covering—tiles or vinyl—have advantages for cooling? Or would laminate flooring actually be the best option for cooling?
We are currently discussing the supply temperature for the underfloor heating system with our prefab house provider.
The house is a timber frame panel construction and meets the KFW40 standard.
According to the construction description, the provider sets the supply temperature of the underfloor heating to 35°C (95°F). We mentioned that we consider this outdated for a new build and would prefer a supply temperature of around 30°C (86°F). We were then told that with a supply temperature of 30°C (86°F), a larger heat pump and a completely different heating system design would be required, and the additional costs could quickly reach five figures. Such extra costs obviously would not make financial sense.
Until now, I thought the supply temperature was primarily determined by the pipe spacing and would be lower if the pipe spacing was reduced.
Why could a lower supply temperature lead to a larger heat pump? What am I missing?
I should add that the heating load calculation and the exact determination of the heat pump have yet to be done. In any case, a Vaillant Arotherm Plus will be used.
Additionally, a question about the floor covering.
We know that tiles are optimal for underfloor heating but vinyl is almost equivalent. We will also have an active underfloor cooling system installed (via the air-to-water heat pump). Does either floor covering—tiles or vinyl—have advantages for cooling? Or would laminate flooring actually be the best option for cooling?
H
Hausbau55EE10 Mar 2023 21:39RotorMotor schrieb:
Have you calculated this, tested it, or is it just a feeling?Are you that confident in your approach? I haven’t calculated it, but my common sense tells me so. I’m happy to read through your calculation now.K
KarstenausNRW10 Mar 2023 21:50Allthewayup schrieb:
He said that 35°C (95°F) must be used as a basis because that is what the standard requires. This is another example of how the general contractor (GC) takes the easy way out so you, as the client, don’t question further.
Because a) there is no such standard, and b) the 35 degrees come from a DIN standard and refer to the maximum surface temperature for underfloor heating (applicable to edge areas, 29 degrees (84°F) for main areas).
It’s just frustrating how you are brushed off like that...
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HoisleBauer2210 Mar 2023 22:37Hausbau55EE schrieb:
but my common sense tells me Physics definitely has an answer. I guess it’s the law of conservation of energy? The heat energy from the pipes under the polystyrene support of the bathtub has to go somewhere. Whether it goes into the concrete ceiling / screed or elsewhere, the energy stays inside the house. Whether you can actually feel it in the bathroom is another question. Or am I mistaken? Another point to consider: with mechanical ventilation with heat recovery, the warmth is also distributed throughout the house...
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HoisleBauer2210 Mar 2023 22:40Regarding the thread topic: The most important insight for me so far in the discussion is that the investment (with a general contractor: several thousand euros) is never worthwhile. For the few months when you actually need heating... Ideally, you have a photovoltaic system that reduces energy costs during the colder months...
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RotorMotor10 Mar 2023 22:41HoisleBauer22 schrieb:
Physics certainly has an answer. I’d guess the law of conservation of energy? The thermal energy from the pipes under the polystyrene support of the bathtub goes somewhere. Whether into the concrete ceiling / screed or elsewhere – the energy stays inside the house. With polystyrene under and above the pipes, the energy primarily stays in the water and returns through the return line. The main issue, as mentioned, is that the 30m (98 feet) of pipe under the bathtub restricts the flow. So, they don’t really release heat but do reduce the flow throughout the entire loop, which lowers the performance of that loop.
HoisleBauer22 schrieb:
And something else to consider: with controlled mechanical ventilation, the heat is also distributed around the house... The effect is very small.
HoisleBauer22 schrieb:
And ideally, you have photovoltaic panels that reduce energy costs during the cooler months... Yeah, you should have photovoltaic panels, but especially when the heat pump has to work hard, usually there’s little to no energy coming from the roof.
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Daniel-Sp10 Mar 2023 22:44HoisleBauer22 schrieb:
And one more thing to consider: With controlled residential ventilation, the heat is also distributed throughout the house... Exactly, warm air is drawn out from the room with the highest desired temperature, the bathroom, and cooler air from the rooms with lower desired temperatures flows in.
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