ᐅ Combination of ventilation system and solar system for domestic hot water?
Created on: 29 Apr 2013 10:17
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watislavHello,
we are planning to build a new house, a one-and-a-half-story single-family home, approximately 140m² (1,507 sq ft).
We want to achieve KfW 70 energy standard and therefore plan to install a solar system for domestic hot water and a central ventilation system with heat recovery. Heating will be provided by a gas condensing boiler. The ground floor, plus the bathroom on the upper floor, will have underfloor heating. We want to use radiators only in the bedrooms and children’s rooms, as we find underfloor heating too slow in those rooms.
My first question: Is this setup reasonable, or is there any fundamental mistake in this approach?
The second question is a bit more general.
At the moment, I don’t have a clear picture of the hot water circuit: so the solar system, gas condensing boiler, underfloor heating, radiators, shower water, dishwashing water. Underfloor heating usually operates with a low supply temperature, around 28°C (82°F). How should the radiators be designed for this? And how is hot water supplied for dishwashing and for the bathtub/shower?
I hope you can help us.
we are planning to build a new house, a one-and-a-half-story single-family home, approximately 140m² (1,507 sq ft).
We want to achieve KfW 70 energy standard and therefore plan to install a solar system for domestic hot water and a central ventilation system with heat recovery. Heating will be provided by a gas condensing boiler. The ground floor, plus the bathroom on the upper floor, will have underfloor heating. We want to use radiators only in the bedrooms and children’s rooms, as we find underfloor heating too slow in those rooms.
My first question: Is this setup reasonable, or is there any fundamental mistake in this approach?
The second question is a bit more general.
At the moment, I don’t have a clear picture of the hot water circuit: so the solar system, gas condensing boiler, underfloor heating, radiators, shower water, dishwashing water. Underfloor heating usually operates with a low supply temperature, around 28°C (82°F). How should the radiators be designed for this? And how is hot water supplied for dishwashing and for the bathtub/shower?
I hope you can help us.
Hello,
Radiators are ideal when quick heating is needed, i.e. for ad hoc use. Depending on the building’s insulation standard, savings can be achieved this way. With better insulation up to a certain intermediate range, this advantage disappears, only to reappear, for example, in a passive house again.
A mixed system is rarely beneficial, as it does not allow you to fully exploit the advantages of either type of heating surface. The supply temperature is determined by the radiators, since their heating surface is smaller. For the underfloor heating, an additional heating circuit (mixing valve) with components (additional investment and consumption) is then necessary.
Technically this is easily feasible but overall remains a compromise.
Also, it will likely not be easy to ensure reliable operation of a gas condensing boiler at this supply temperature!
Heating and domestic hot water, despite sharing a common heat generator, have separate consumption circuits that operate alternately with different supply temperatures!
Regards,
NB: All heating surfaces and hydraulics must be sized according to the room heating loads. A heating load calculation according to DIN 12831 is mandatory; otherwise, it will be a mess!
watislav schrieb:A solar thermal system would not be an option for me, as it is usually not very economical in a single-family house. However, it is sufficient on paper.
...We want to achieve KfW 70 standard and therefore plan to install a solar system for domestic hot water and a central ventilation system with heat recovery. A gas condensing boiler is intended for heating.
watislav schrieb:Based on what criteria does that make sense? There are competing requirements!
...The ground floor, plus the bathroom on the upper floor, should be equipped with underfloor heating. We only want to use radiators in the bedroom and children’s rooms, as underfloor heating feels too slow there.
Radiators are ideal when quick heating is needed, i.e. for ad hoc use. Depending on the building’s insulation standard, savings can be achieved this way. With better insulation up to a certain intermediate range, this advantage disappears, only to reappear, for example, in a passive house again.
A mixed system is rarely beneficial, as it does not allow you to fully exploit the advantages of either type of heating surface. The supply temperature is determined by the radiators, since their heating surface is smaller. For the underfloor heating, an additional heating circuit (mixing valve) with components (additional investment and consumption) is then necessary.
Technically this is easily feasible but overall remains a compromise.
watislav schrieb:I would like to see that with a KfW 70 standard—at best in a sunny southern European location! By the way, underfloor heating feels cold at that temperature! You won’t get warm feet.
...?An underfloor heating system operates with a low supply temperature, usually around 28°C (82°F).
Also, it will likely not be easy to ensure reliable operation of a gas condensing boiler at this supply temperature!
Heating and domestic hot water, despite sharing a common heat generator, have separate consumption circuits that operate alternately with different supply temperatures!
Regards,
NB: All heating surfaces and hydraulics must be sized according to the room heating loads. A heating load calculation according to DIN 12831 is mandatory; otherwise, it will be a mess!
A solar thermal system is now offered as a standard option by most construction companies. The question is whether it is still easy to achieve KfW 70 standard without a solar thermal system.
Okay, 28°C (82°F) as the supply temperature might be a bit low. However, I forgot to mention that we are considering designing the underfloor heating in a way that would allow switching to a heat pump in the future.
Based on your statements, I conclude that it probably makes more sense to choose underfloor heating completely. Is underfloor heating compatible with cork flooring?
And once again, the question about the domestic hot water circuit: If the gas condensing boiler has a separate circuit for the domestic hot water, what are the advantages of having a separate circuit for the radiators?
Okay, 28°C (82°F) as the supply temperature might be a bit low. However, I forgot to mention that we are considering designing the underfloor heating in a way that would allow switching to a heat pump in the future.
Based on your statements, I conclude that it probably makes more sense to choose underfloor heating completely. Is underfloor heating compatible with cork flooring?
And once again, the question about the domestic hot water circuit: If the gas condensing boiler has a separate circuit for the domestic hot water, what are the advantages of having a separate circuit for the radiators?
1) Two systems are probably not economical enough.
2) Cork flooring is said to be well suited for underfloor heating (probably somewhat better than hardwood flooring because it is not as thick).
3) It probably works better with improved insulation. We decided against it because the insulation in the attic takes up too much height.
2) Cork flooring is said to be well suited for underfloor heating (probably somewhat better than hardwood flooring because it is not as thick).
3) It probably works better with improved insulation. We decided against it because the insulation in the attic takes up too much height.
watislav schrieb:
...Nowadays, most construction companies include solar thermal systems as a standard offer. That is correct, because it is simple and convenient – but for whom? watislav schrieb:
...The question is whether KfW 70 can still be easily achieved without a solar thermal system. It can be done; whether it is easy depends on the specific conditions of the building project. watislav schrieb:
..., to design the underfloor heating from the start so that switching to a heat pump in the future might be possible. That is not unreasonable. watislav schrieb:
...Does underfloor heating work well with cork flooring? For suitability of materials, the respective manufacturers can provide information. On the other hand, the more insulating the underfloor surface covering, the less efficient the underfloor heating and the more expensive it becomes. Ideally, well heat-conductive surface coverings such as tiles, granite, or polished concrete are used. watislav schrieb:
...If the gas condensing boiler has a separate circuit for domestic hot water, what would be the advantage of a separate circuit for the radiators? Generally, there are only two externally run supply options (heating, domestic hot water). Internally, on the boiler side, there is usually only one circuit, followed by an internal three-way valve that, depending on demand and controlled by the system, switches alternatively between heating or domestic hot water. Best regards.
€uro schrieb:
There are usually only two options for externally routed supply lines (heating, domestic hot water). Internally on the boiler side, there is typically only one, followed by an internal three-way valve that is controlled by the system regulation to switch as needed between heating or domestic hot water.
v.g.How do towel radiators actually work in this context? With a supply temperature of around +/- 30°C (86°F) and a relatively limited surface area, I assume they provide only a small amount of heat?
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