ᐅ Combination of ventilation system and solar system for domestic hot water?
Created on: 29 Apr 2013 10:17
W
watislav
Hello,
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.
Musketier schrieb:
How do towel radiators actually work in this context? With a supply temperature of around 30°C (86°F) and a relatively small surface area, I guess they don’t provide much heat? Correct, in this case they act more as towel warmers. Their contribution to meeting the room heating load is very limited, especially when covered with towels. A similar situation occurs with underfloor heating => limited or inactive heating surfaces, which is typical for bathrooms or kitchens. This must be taken into account by the designer when sizing the heating surfaces.
Best regards
M
Micha&Dany30 Apr 2013 05:58Musketier schrieb:
How do towel warmers actually work in this context? With a supply temperature of around 30°C (86°F) and a limited surface area, I guess they don’t provide much heat?Hello Musketier,
In our case, they are purely electric.
They are not connected to the heating system.
The advantage is that you can turn the warmer on before the children take a bath to quickly heat the room, or while showering to preheat the towels.
Operating costs? We’ll see. This is one of the aspects where I prioritized comfort over cost efficiency.
Regards,
Micha
M
Micha&Dany30 Apr 2013 06:04watislav schrieb:
The question is whether KfW 70 can still be easily achieved without a solar thermal system.Hello Watislav
Yes, it can.
As an example (not to be generalized):
I had to increase the roof insulation from 20 cm to 24 cm (8 inches to 9.5 inches) in order to comply with KfW 70 and the Renewable Energy Heat Act.
In return, I saved the cost of a solar thermal system and now have the entire south-facing roof area free for photovoltaics.
I don’t yet have the final invoice from my builder, but anyone can imagine that adding 4 cm (1.5 inches) more insulation material (installation labor/time remains the same) instead of a solar thermal system results in significant cost savings, including the financing costs for this amount.
So it is definitely worth having the 15% rule checked. In many cases, it should offer a huge advantage!
Best regards Micha
D
DerBjoern30 Apr 2013 10:15If you want a solar thermal system for ideological reasons, then just go ahead and get it. Whether you save money with insulation instead of a solar thermal system or end up spending more depends on your specific house project and can only be answered by your planner/provider.
B
Bauexperte30 Apr 2013 10:41Hello,
Regards, Bauexperte
Micha&Dany schrieb:If I were you, I wouldn’t be so quick to decide; I’m already looking forward to your post on the topic once the final invoice is available.
... but everyone can probably imagine that using 4cm (1.5 inches) more material (installation work/time remains the same) instead of a solar thermal system is an extreme cost saving. (including costs for the loan/financing of this amount).
Regards, Bauexperte