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 We mentioned that we consider this outdated for a new build and would prefer a supply temperature of around 30°C (86°F).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 We mentioned that we consider this outdated for a new build and would prefer a supply temperature of around 30°C (86°F).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?
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xMisterDx11 Mar 2023 20:23By the way, the natural outdoor temperature (NAT) currently ranges between -8 and -18°C (17.6 and 0.4°F), depending on the district. Anyone designing their supply temperature based on 30°C (86°F) at this value... there is no saving them.
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WilderSueden11 Mar 2023 22:57Allthewayup schrieb:
With the knowledge I have today, I would do it the same way, but just a year ago I had zero understanding of most topics. However, a second house build will probably only happen in the next life; I won’t put my family through that again. ;-) How was it again... the first one for the enemy, the second for the friend, and the third for yourself?
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Hausbau55EE12 Mar 2023 10:47xMisterDx schrieb:
By the way, the outside temperature is currently between -8 and -18°C (17.6 and 0.4°F), depending on the district.
Anyone designing their supply temperature at 30°C (86°F) based on this... there’s no helping them anymore. Your generalization doesn’t help anyone either, especially since you haven’t shared your reasoning with us.
Obviously, some users are looking for ways to reduce the supply temperature below 35°C (95°F). As already discussed in the thread, it doesn’t have to be 30°C (86°F). But 32°C (90°F) would be a good result, at least from my point of view.
In the whole discussion about general contractor (GC) versus individual contracting, it’s important to remember that you never really have a direct comparison.
There are definitely some issues that have upset us, which we didn’t know about beforehand, and there were times when I thought, “Man – now I’m building a house for so much money and I can’t even plan everything exactly as I want. Why didn’t I just build with an architect?”
But a) you simply don’t know what could have gone wrong with an architect or how much more expensive it might have been. Certainly, some things would have been planned or executed differently, but it probably would have caused even more stress and effort. At least with the GC, we have a fixed price from early 2022 that still holds today. Nobody can tell me how last year’s price increases would have impacted us if we had built with an architect. That’s why I still believe it was the right decision to build with a GC. Compromises are just part of it – some home builders may be more flexible, others less so.
Regarding the supply water temperature, I’ll wait for the calculation first and then get the plans before deciding what to do next.
For example, it would be great if I could convince our GC to install underfloor heating in the shower area. 😉
@OWLer How satisfied or dissatisfied are you with your Vaillant?
@Tolentino Apart from the controls, are you happy with the noise level and so on?
There are definitely some issues that have upset us, which we didn’t know about beforehand, and there were times when I thought, “Man – now I’m building a house for so much money and I can’t even plan everything exactly as I want. Why didn’t I just build with an architect?”
But a) you simply don’t know what could have gone wrong with an architect or how much more expensive it might have been. Certainly, some things would have been planned or executed differently, but it probably would have caused even more stress and effort. At least with the GC, we have a fixed price from early 2022 that still holds today. Nobody can tell me how last year’s price increases would have impacted us if we had built with an architect. That’s why I still believe it was the right decision to build with a GC. Compromises are just part of it – some home builders may be more flexible, others less so.
Regarding the supply water temperature, I’ll wait for the calculation first and then get the plans before deciding what to do next.
For example, it would be great if I could convince our GC to install underfloor heating in the shower area. 😉
@OWLer How satisfied or dissatisfied are you with your Vaillant?
@Tolentino Apart from the controls, are you happy with the noise level and so on?
a) However, in the recommended standard, the architect is also responsible for construction management and is supposed to ensure that all trades coordinate properly. The general contractor’s site manager works in the interest of the general contractor and often proves less helpful to the client than a dedicated construction manager.
b) Most price increases occurred in 2021. In 2022, many prices have already gone down again. You can assume that a fixed price contract from 2022 already comfortably includes all actual price increases plus a contingency allowance based on recent experience. This is also reflected in the many threads in this forum where general contractors try to push through change orders despite fixed-price contracts or use delay tactics to avoid fixed-price deadlines. However, one should not generalize. There are also positive examples, such as the general contractor of @kati1337, for instance. Likewise, there are of course poor architects. I argue that you can already recognize such issues earlier in the process or still maintain more control over the entire project than when working with a general contractor alone. Once the withdrawal period has expired, you are practically at the mercy of the general contractor. With an architect, you still have the option to handle individual construction phases differently.
I hope your general contractor is one of the good ones. For clients in the pre-contract phase, I would nowadays always recommend managing construction via separate contracts. I also consider it useful to hire an additional construction consultant if you yourself are an unexperienced layperson.
b) Most price increases occurred in 2021. In 2022, many prices have already gone down again. You can assume that a fixed price contract from 2022 already comfortably includes all actual price increases plus a contingency allowance based on recent experience. This is also reflected in the many threads in this forum where general contractors try to push through change orders despite fixed-price contracts or use delay tactics to avoid fixed-price deadlines. However, one should not generalize. There are also positive examples, such as the general contractor of @kati1337, for instance. Likewise, there are of course poor architects. I argue that you can already recognize such issues earlier in the process or still maintain more control over the entire project than when working with a general contractor alone. Once the withdrawal period has expired, you are practically at the mercy of the general contractor. With an architect, you still have the option to handle individual construction phases differently.
I hope your general contractor is one of the good ones. For clients in the pre-contract phase, I would nowadays always recommend managing construction via separate contracts. I also consider it useful to hire an additional construction consultant if you yourself are an unexperienced layperson.
JohnnyEH schrieb:
As for the flow temperature, I will first wait for the calculation, get the plans, and then decide how to proceed.Then check the bathroom floor area to see if the shower is included; if it is, that's standard and won’t incur an extra charge. We’re glad not to have to stand on cold tiles when showering.
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