ᐅ Heating System Choice: Air-to-Air or Air-to-Water Heat Pump
Created on: 19 Jun 2023 11:18
K
KatlarOne
Hello everyone,
we are just at the very beginning of our home building journey – specifically in choosing the construction company. Neither of us are experts, and we are currently educating ourselves a lot -> please excuse us if some technical terms are unfamiliar or used incorrectly 😉
Among many other questions, we are uncertain about the heating system.
Construction Company A strongly recommends an air-to-air heat pump – meaning a central ventilation system with 'heating through the air flow.'
Company B suggests an air-to-water heat pump – combined with underfloor heating + still a central ventilation system.
And now about our lack of knowledge…
The air-to-air solution seems initially cheaper – but according to the advisor from Company B, there are disadvantages:
- Every room is the same temperature -> so having a cold bedroom and warm living room wouldn’t be possible?
- Warm air always rises -> so the floor would feel cold.
Neither of these issues would occur with underfloor heating since it can be controlled separately, and of course, your feet would be warm.
I don’t want to start a (new) fundamental debate – just wondering if you see it the same way? Unfortunately, we don’t know anyone who heats ‘with air’ 😉
we are just at the very beginning of our home building journey – specifically in choosing the construction company. Neither of us are experts, and we are currently educating ourselves a lot -> please excuse us if some technical terms are unfamiliar or used incorrectly 😉
Among many other questions, we are uncertain about the heating system.
Construction Company A strongly recommends an air-to-air heat pump – meaning a central ventilation system with 'heating through the air flow.'
Company B suggests an air-to-water heat pump – combined with underfloor heating + still a central ventilation system.
And now about our lack of knowledge…
The air-to-air solution seems initially cheaper – but according to the advisor from Company B, there are disadvantages:
- Every room is the same temperature -> so having a cold bedroom and warm living room wouldn’t be possible?
- Warm air always rises -> so the floor would feel cold.
Neither of these issues would occur with underfloor heating since it can be controlled separately, and of course, your feet would be warm.
I don’t want to start a (new) fundamental debate – just wondering if you see it the same way? Unfortunately, we don’t know anyone who heats ‘with air’ 😉
W
WilderSueden19 Jun 2023 21:06KatlarOne schrieb:
Apart from the fact that it doesn't necessarily have to be company A or B, was the air-to-air heat pump used for a KFW55 house and the air-to-water heat pump for a "climate-friendly residential building – with QNG," meaning KFW 40+? In combination, I wouldn’t choose the air-to-air heat pump. If you go with an air-to-air heat pump, it should be at least for KFW40. I also think that would be very elegant for a passive house during the coldest 10 days of the year. Whether you then certify it as sustainable and add a battery is another question. Basically, you shouldn’t expect too much from photovoltaic systems in winter—short days, low sun…
K
KatlarOne19 Jun 2023 23:01WilderSueden schrieb:
Basically, you shouldn't expect too much from photovoltaic systems in winter either. Short days, low sun...Even with full roof coverage? I thought that would be enough. So, we actually want to go for KfW40+ with photovoltaic plus battery for the subsidy.
KingJulien19 Jun 2023 23:57KatlarOne schrieb:
'Full coverage' of the roofThat is already a prerequisite for a productive winter, as long as there is no snow on it. Self-sufficiency in summer is something anyone can achieve.
H
HeimatBauer20 Jun 2023 08:57The general statement "roof fully covered" from common photovoltaic groups is not wrong but only tells half the story. In winter, the sun is simply in a different position, and for example, I could of course fully cover my east-west pitched roof, but in winter that would bring me little benefit due to the angle. This is something you can simulate. On the other hand, if I install much less surface area at the correct angle on the south side, I get significantly more.
In general, goals like "absolute one hundred percent self-sufficiency every day of the year" quickly become very expensive. Sure, you can cover unlimited areas and build unlimited storage capacity to comfortably run the sauna even during a week of temperatures below -25°C (-13°F) – but then you are deep into hobby territory. The other extreme is the "fully covered roof and feed-in" people who still have old contracts with high feed-in tariffs. That works out well financially, but if (as just happened to us) a lightning strike destroys the distribution box, it gets very cold in the house very quickly.
So it is always an individual balance between objective benefit, hobby interest (I don’t mean this negatively; my system also has some elements “because I want it”) and the available budget.
In general, goals like "absolute one hundred percent self-sufficiency every day of the year" quickly become very expensive. Sure, you can cover unlimited areas and build unlimited storage capacity to comfortably run the sauna even during a week of temperatures below -25°C (-13°F) – but then you are deep into hobby territory. The other extreme is the "fully covered roof and feed-in" people who still have old contracts with high feed-in tariffs. That works out well financially, but if (as just happened to us) a lightning strike destroys the distribution box, it gets very cold in the house very quickly.
So it is always an individual balance between objective benefit, hobby interest (I don’t mean this negatively; my system also has some elements “because I want it”) and the available budget.
KingJulien20 Jun 2023 15:51Full agreement.
The major advantage of a fully pitched roof becomes apparent especially on cloudy days or during foggy conditions.
Calculations often assume the sun shines 365 days a year.
With an overcast sky, the angle and orientation are fairly irrelevant.
In this case, double the surface area equals almost double the yield.
Of course, for economic efficiency, the angle still needs to be reasonably appropriate for sunlight, that goes without saying.
But there are plenty of software programs available to simulate this.
The major advantage of a fully pitched roof becomes apparent especially on cloudy days or during foggy conditions.
Calculations often assume the sun shines 365 days a year.
With an overcast sky, the angle and orientation are fairly irrelevant.
In this case, double the surface area equals almost double the yield.
Of course, for economic efficiency, the angle still needs to be reasonably appropriate for sunlight, that goes without saying.
But there are plenty of software programs available to simulate this.
R
RotorMotor20 Jun 2023 16:26Where does a full roof system not make sense?
The price usually decreases with larger systems.
You only need one scaffold, (usually) just one inverter, one setup, etc.
Therefore, it is very, very rarely practical to stop at half!
The price usually decreases with larger systems.
You only need one scaffold, (usually) just one inverter, one setup, etc.
Therefore, it is very, very rarely practical to stop at half!
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