ᐅ Gas with solar thermal? Or heat pump with photovoltaic? Advice needed
Created on: 5 Feb 2020 08:57
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Micha8589
Good morning to the forum,
I have been researching heating options for quite some time and have gathered a few opinions, which have only made me more uncertain about my decision. That’s why I thought I’d ask the forum.
My family (2 adults, 1 child) is planning to build the following single-family house at the end of this year or beginning of next year:
Single-family home with pitched roof
Approximately 115 m² (1,237 sq ft)
Solid construction (calcium silicate brick ground and upper floors, brick-clad)
No KFW standard
Building location: southern Mecklenburg
Unfortunately, I can’t provide an energy performance certificate or heating load calculation yet, as the preliminary offer is still being prepared. I am also aware that a general statement can’t really be made since every house and heating behavior is individual.
The construction company advised us to install a modern hybrid heating system consisting of a gas condensing boiler and two solar thermal panels on the roof for domestic hot water, as the initial costs are relatively low (plus installation of the central gas connection), and this technology has proven reliable. The entire house is planned to have underfloor heating. According to the company, they have had very positive experiences with this and consider the technology future-proof. (There is also the idea of a fireplace in the living room.)
On the other hand, I think gas prices will not get any cheaper in the future, and the topic of CO₂ taxes (especially concerning the fireplace) worries me somewhat.
In theory, I would prefer to install a geothermal heat pump combined with a suitable photovoltaic system because this would make me independent of fossil fuels and allow me to heat “off-grid” to a certain extent, depending on efficiency. However, I am hesitant because of the very high initial costs and don’t really know how these compare to operational costs. I also can no longer realistically assess which technology offers the best cost-performance ratio (except for air-source heat pumps).
As you can see, I am completely undecided and hope to get some feedback and expertise from the forum.
Thanks in advance for your replies.
I have been researching heating options for quite some time and have gathered a few opinions, which have only made me more uncertain about my decision. That’s why I thought I’d ask the forum.
My family (2 adults, 1 child) is planning to build the following single-family house at the end of this year or beginning of next year:
Single-family home with pitched roof
Approximately 115 m² (1,237 sq ft)
Solid construction (calcium silicate brick ground and upper floors, brick-clad)
No KFW standard
Building location: southern Mecklenburg
Unfortunately, I can’t provide an energy performance certificate or heating load calculation yet, as the preliminary offer is still being prepared. I am also aware that a general statement can’t really be made since every house and heating behavior is individual.
The construction company advised us to install a modern hybrid heating system consisting of a gas condensing boiler and two solar thermal panels on the roof for domestic hot water, as the initial costs are relatively low (plus installation of the central gas connection), and this technology has proven reliable. The entire house is planned to have underfloor heating. According to the company, they have had very positive experiences with this and consider the technology future-proof. (There is also the idea of a fireplace in the living room.)
On the other hand, I think gas prices will not get any cheaper in the future, and the topic of CO₂ taxes (especially concerning the fireplace) worries me somewhat.
In theory, I would prefer to install a geothermal heat pump combined with a suitable photovoltaic system because this would make me independent of fossil fuels and allow me to heat “off-grid” to a certain extent, depending on efficiency. However, I am hesitant because of the very high initial costs and don’t really know how these compare to operational costs. I also can no longer realistically assess which technology offers the best cost-performance ratio (except for air-source heat pumps).
As you can see, I am completely undecided and hope to get some feedback and expertise from the forum.
Thanks in advance for your replies.
There are, of course, many different configurations. You can build it one way or another. Typically, the solar thermal system (ST) is more of a supplementary solar setup—just large and with as much hydraulics as needed to comply with the energy saving regulations. Usually, it is mainly used for domestic hot water production.
It also makes little sense to use solar thermal for space heating because when you need heating, there is no sun, and when there is plenty of sun, you don’t need heating. Additionally, solar thermal can easily heat the water up to 70°–80°C (158°–176°F), but underfloor heating only requires about 30°C (86°F). This then requires safety groups and mixing valves, which ultimately leads to higher operating costs and increased investment. Not to mention the extra space needed—meaning more square meters in the utility room. Two storage tanks are not necessary.
I also see it slightly differently than nordanney. Hot water is not only abundant in summer but for about three-quarters of the year. In summer, you can even use it to operate the pool with “free” hot water if needed or desired.
It also makes little sense to use solar thermal for space heating because when you need heating, there is no sun, and when there is plenty of sun, you don’t need heating. Additionally, solar thermal can easily heat the water up to 70°–80°C (158°–176°F), but underfloor heating only requires about 30°C (86°F). This then requires safety groups and mixing valves, which ultimately leads to higher operating costs and increased investment. Not to mention the extra space needed—meaning more square meters in the utility room. Two storage tanks are not necessary.
I also see it slightly differently than nordanney. Hot water is not only abundant in summer but for about three-quarters of the year. In summer, you can even use it to operate the pool with “free” hot water if needed or desired.
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Iotafreak3 Nov 2020 14:16Mycraft schrieb:
Of course, there are all kinds of different setups. You can build it one way or another. Usually, the solar thermal system is just a minimal setup—only as large and with as much hydraulics as necessary to comply with the energy saving regulations. Most often, it’s used only for domestic hot water production.
Using solar thermal for space heating doesn’t make much sense, because when you need heating, there is no sun, and when there is plenty of sun, you don’t need heating. Another complication is that solar thermal easily heats water up to 70°-80°C (158°-176°F), but underfloor heating only requires about 30°C (86°F). This then requires safety devices and mixing valves, which ultimately lead to higher operating costs and additional investment. Not to mention the extra space needed, meaning more square meters in the utility room. Two storage tanks are not necessary.
I also have a somewhat different view than nordanney. You don’t only have an abundance of hot water in the summer but for about three-quarters of the year. In summer, you can even use the hot water to operate a pool "for free," if needed or desired. Okay, thanks for the explanation... Once we’ve completed the notary appointment for the land purchase, I’ll probably be visiting this forum daily.
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motorradsilke4 Dec 2020 18:23I’ll join in here. We are planning to build a new single-family home, a bungalow, and want to start construction next year. We have already gathered several quotes, and there are different opinions regarding the heating system. We actually want a gas condensing boiler since we already have gas on the property and also want to use gas for cooking. Some providers have told us that we can use a gas condensing boiler combined with two solar collectors for domestic hot water. However, yesterday a builder explained that according to the new building energy regulation, this is no longer allowed, and at least a heat pump must be used. Can someone reassure me? Or is this really the case? I’m having trouble understanding the building energy regulation itself.
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T_im_Norden4 Dec 2020 18:32If I remember correctly, the requirements are actually a bit lower. Gas should still be allowed; ask your contractor to show you the clause where this is stated.
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Pinkiponk4 Dec 2020 19:08motorradsilke schrieb:
... Yesterday, a contractor explained to us that according to the new building energy law, this is no longer allowed, and at least a heat pump must be used.
...We are also building a prefabricated house next year in the federal state of Saxony. According to our house purchase contract, we can or must combine a gas condensing boiler with solar thermal. This is also stated in the building permit / planning permission application, which we submitted this week. I didn’t explicitly ask about this because the situation you described does not match my knowledge, but I would be surprised if neither the architect nor the house manufacturer were aware of it. As far as I understand, nothing about a heat pump is mentioned in the building permit / planning permission application.M
motorradsilke5 Dec 2020 09:17Thank you all for the answers; that puts me at ease for now.
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