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.
M
Micha&Dany30 Apr 2013 12:39Bauexperte schrieb:
Hello,
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
Regards, BauexperteHello Bauexperte,
Why??
I don’t have an exact idea of what a solar thermal system costs, but I’d estimate it to be around 5,000 euros (5,000 USD). Is that about right?
Please don’t tell me that the material cost for 4 cm (1.6 inches) of insulation is 5,000 euros (5,000 USD)! That would mean the 20 cm (8 inches) of insulation I already planned would have cost 25,000 euros (25,000 USD) just for materials! I can’t imagine that...
As I said – there’s no difference in installation, labor costs, or time whether you install 20 or 24 cm (8 or 9.5 inches). So the net difference is really just the material cost.
Next time I am at the hardware store, I’ll check the prices for insulation there.
Greetings from the Ruhr area
Micha
D
DerBjoern30 Apr 2013 13:14@Micha&Dany
You can’t simply say that adding 4cm (1.5 inches) more insulation in the roof is enough. Depending on the house, various other measures might be necessary, depending on how it was originally planned. If the entire insulation was already installed to the limit, then just increasing the roof insulation thickness by 20% won’t be sufficient. The house isn’t made up of the roof alone. Even when only increasing the roof insulation, additional costs can arise beyond the difference between 20cm (8 inches) and 24cm (9.5 inches) insulation. For example, if you have 20cm (8 inches) of insulation between rafters and want to increase it to 24cm (9.5 inches), but the rafters themselves are only 20cm (8 inches) deep, you will need an additional 4cm (1.5 inches) of insulation below the rafters. This includes counter battens, extra work, and so on. And if such changes are made only after signing a contract with a general contractor / main contractor / developer, the price will be whatever they decide to charge.
There are many factors that can influence this. So, claiming that it will save a few thousand euros just by leaving out the solar thermal system is, in my opinion, careless...
You can’t simply say that adding 4cm (1.5 inches) more insulation in the roof is enough. Depending on the house, various other measures might be necessary, depending on how it was originally planned. If the entire insulation was already installed to the limit, then just increasing the roof insulation thickness by 20% won’t be sufficient. The house isn’t made up of the roof alone. Even when only increasing the roof insulation, additional costs can arise beyond the difference between 20cm (8 inches) and 24cm (9.5 inches) insulation. For example, if you have 20cm (8 inches) of insulation between rafters and want to increase it to 24cm (9.5 inches), but the rafters themselves are only 20cm (8 inches) deep, you will need an additional 4cm (1.5 inches) of insulation below the rafters. This includes counter battens, extra work, and so on. And if such changes are made only after signing a contract with a general contractor / main contractor / developer, the price will be whatever they decide to charge.
There are many factors that can influence this. So, claiming that it will save a few thousand euros just by leaving out the solar thermal system is, in my opinion, careless...
Hello,
Although this no longer directly relates to the original topic of underfloor heating/radiator heating, I would like to add the following.
These are two completely different matters being discussed here.
Insulation reduces the heating energy demand, while a solar thermal system more or less reliably substitutes consumption (usually domestic hot water or domestic hot water/heating).
In order to be able to compare the investments in each case, the demand and consumption must first be determined.
Solar thermal systems have, among other things, the disadvantage that the theoretical values often differ significantly from actual results. The reasons for this are varied. Furthermore, additional components such as controls, pumps, hydraulics, etc., are required.
For those who accept only the theoretical data for a solar thermal system, I recommend a heat meter to compare the actual yield with the supplier’s performance forecast.
Best regards.
Although this no longer directly relates to the original topic of underfloor heating/radiator heating, I would like to add the following.
These are two completely different matters being discussed here.
Insulation reduces the heating energy demand, while a solar thermal system more or less reliably substitutes consumption (usually domestic hot water or domestic hot water/heating).
In order to be able to compare the investments in each case, the demand and consumption must first be determined.
Solar thermal systems have, among other things, the disadvantage that the theoretical values often differ significantly from actual results. The reasons for this are varied. Furthermore, additional components such as controls, pumps, hydraulics, etc., are required.
For those who accept only the theoretical data for a solar thermal system, I recommend a heat meter to compare the actual yield with the supplier’s performance forecast.
Best regards.
B
Bauexperte1 May 2013 10:33Hello Micha,
If at the end of the day there is more money available, great—please let us know.
Regards, Bauexperte
Micha&Dany schrieb:I would be surprised; I’m thinking more like 3,500–3,700 euros.
Why??
I don’t have a precise idea of what a solar thermal system costs, but I would estimate the whole thing to be around 5,000 euros. Is that about right?
Micha&Dany schrieb:As "Der Bjoern" correctly points out, it’s not "just" about adding 4 cm (1.6 inches) of insulation; to comply with the 15% rule, a bit more is involved. However, I won’t speculate on that here since I don’t know your contracts or the planned execution. My only intention was to advise caution before getting too optimistic, as I have often seen excitement dampened by the actual figures provided. Especially when it comes to reimbursements after the contract has been signed.
Please don’t tell me that the material costs for 4 cm (1.6 inches) of insulation are 5,000 euros?!
If at the end of the day there is more money available, great—please let us know.
Regards, Bauexperte
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