ᐅ Lowering the Supply Temperature in Underfloor Heating Systems More Complex Than Expected?
Created on: 9 Mar 2023 22:07
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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 We mentioned that we consider this outdated for a new build and would prefer a supply temperature of around 30°C (86°F).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 We mentioned that we consider this outdated for a new build and would prefer a supply temperature of around 30°C (86°F).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?
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HoisleBauer2211 Mar 2023 11:49Addition: When you search for "building law right to plans," you will find, for example, an entry by Mr. Heide who cites several court rulings. This concerns Section 650n of the Building Code. It should be possible to obtain all energy-related plans. Because: "The thermal insulation certificate and calculation according to the Energy Saving Ordinance 2002" is also required according to the Higher Regional Court Dresden, ruling dated May 12, 2016 – 8 U 438/15. To verify this, I need the heating plans.
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Daniel-Sp11 Mar 2023 12:11Hausbau55EE schrieb:
With 2 exhaust air fans in the bathroom and controlled mechanical ventilation, maintaining 24°C (75°F) in the bathroom while keeping 20°C (68°F) in all other rooms becomes a real challenge??? Of course, that largely depends on the planning. If, as is often the case, the system is designed with reduced heating output, it won’t get any easier to reach that temperature. If, as is often the case, planning and construction are done roughly “by rule of thumb” simply because it’s always been done that way,...
The question is whether the calculations are done correctly, or if the manufacturer of the underfloor heating system just provides a standard plan with default values. The latter is usually the case with general contractors.
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WilderSueden11 Mar 2023 16:13HoisleBauer22 schrieb:
No one can legally prevent you from inspecting the execution of the construction work. You are always allowed to inspect the work. But if the executed solution 1. complies with the building specifications, 2. is legal, and 3. follows the recognized technical standards, you have no right to demand changes, even if another solution would be better. This is one reason why I would build only with individual contracting rather than a general contractor again.
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Allthewayup11 Mar 2023 17:27WilderSueden schrieb:
You are always allowed to inspect the workmanship. However, if the executed solution 1. matches the building specification, 2. is legal, and 3. complies with recognized technical standards, you have no right to demand changes—even if another method would be better. This is one reason why I would no longer build with a general contractor, but only with individual contracts. With the knowledge I have today, I would do the same, but just a year ago I had zero understanding of most of these topics. The second house build will probably only happen in another life; I’m not putting my family through that again. ;-)
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xMisterDx11 Mar 2023 20:15WilderSueden schrieb:
You are always allowed to inspect the workmanship. But if the executed solution 1. matches the building description, 2. is legal, and 3. complies with the recognized rules of technology, you have no right to demand changes—even if another solution would be better. This is one reason why I would only build with individual contracts, not with a general contractor. If you had built your project with individual contracts, given the chaos of recent years, you would have been lucky just to celebrate the topping out ceremony by now, and it would have already cost you about 30% more.
Therefore, this is mostly an academic discussion.
The contract is signed, and any changes cost whatever the provider charges.
If they quote 30,000 EUR for the new heating system, you can either agree or not.
And this is not unusual. For example, with a VW Golf Trendline, VW barely makes any profit; most of their profit comes from optional extras, such as rims for 2,500 EUR, which they get from suppliers for 1,000 EUR.
This also happened at gas stations. When they have almost no fuel left of a certain type, they set the price to 9.99 EUR, as the display cannot show more. For cases where someone absolutely HAS to refuel, for whatever reason. This way, they keep a small reserve for emergencies.
And anyone who then fills up, out of carelessness or whatever, actually pays 9.99 EUR, not a cent less. There are court rulings on this.
The seller sets the price, and the buyer can either accept or decline.