Hello everyone,
I wanted to ask for your opinion. In our new build, an air-to-water heat pump from Vaillant or an equivalent brand will be installed.
Since we are currently not considering air conditioning, we are thinking about using the heat pump for some cooling. Of course, it’s no comparison to a dedicated air conditioner, but at least a little cooling, right?
I would like the heat pump to operate in reverse mode to expel warm air outside. At the same time, my partner doesn’t want a “freezing cold” underfloor heating. Besides, the warm air naturally stays “up top.”
Can you still recommend something, or would you advise against this entirely?
Thanks for your help.
I wanted to ask for your opinion. In our new build, an air-to-water heat pump from Vaillant or an equivalent brand will be installed.
Since we are currently not considering air conditioning, we are thinking about using the heat pump for some cooling. Of course, it’s no comparison to a dedicated air conditioner, but at least a little cooling, right?
I would like the heat pump to operate in reverse mode to expel warm air outside. At the same time, my partner doesn’t want a “freezing cold” underfloor heating. Besides, the warm air naturally stays “up top.”
Can you still recommend something, or would you advise against this entirely?
Thanks for your help.
The goal of passive cooling is to remove heat stored in the building’s thermal mass (ceilings, floors, screed, etc.). Heat storage in air is negligible compared to screed and concrete ceilings, as air is an extremely poor heat reservoir.
That’s why your comparison to briefly running an air conditioner is like comparing apples and oranges. If you only cool the air for a short time after the building mass has already warmed up and then switch off the cooling, the indoor air temperature will naturally rise again quite quickly because everything else in the house remains heated. You can only maintain a consistently low temperature by cooling continuously or at regular intervals—not just briefly (especially when compared to 24-hour continuous passive cooling).
Ultimately, it’s about cooling capacity per electricity consumption. With a brine-water heat pump, the coefficient of performance is about 1:40 to 1:80. Unfortunately, linking is not allowed, but as mentioned several times, there are already extensive tests on this topic. These can be easily found by searching the forum where the trench collector was also developed.
That’s why your comparison to briefly running an air conditioner is like comparing apples and oranges. If you only cool the air for a short time after the building mass has already warmed up and then switch off the cooling, the indoor air temperature will naturally rise again quite quickly because everything else in the house remains heated. You can only maintain a consistently low temperature by cooling continuously or at regular intervals—not just briefly (especially when compared to 24-hour continuous passive cooling).
Ultimately, it’s about cooling capacity per electricity consumption. With a brine-water heat pump, the coefficient of performance is about 1:40 to 1:80. Unfortunately, linking is not allowed, but as mentioned several times, there are already extensive tests on this topic. These can be easily found by searching the forum where the trench collector was also developed.
I am familiar with these approaches as well. The concept of including the concrete, for example, was also tempting for us.
I didn’t question the concept but spent a considerable amount of time considering it myself.
It was not discarded for economic or ecological reasons but because we chose a different overall concept. It could not have been integrated effectively here. Radiant floor cooling would not have been an option since my wife always has cold feet anyway.
Air is a poor heat storage medium and heat conductor. However, this applies in both directions.
But the transfer of heat and cold through air is also very slow. Therefore, it is quicker and easier to cool the air itself, which is more important for us as humans. For example, if I cool down the bedroom before going to sleep, it stays cool throughout the night.
At night, the house also releases heat to the outside. As you correctly mentioned, it should be a holistic concept. For example, shading, insulation, controlled ventilation running with an open bypass at night, and so on. This results in additional cooling or less heating. We also pass the air through the ground to cool it further.
Because of this, an air conditioner wouldn’t need to run continuously or would only have to run for shorter periods to achieve the same comfort effect. So the comparison is not irrelevant. A brine-to-water heat pump is more efficient when looking at the theoretical cooling capacity. Even better would be integrating it into the ceiling or walls, resulting in fewer cold feet and a greater effect. Ultimately, the perceived temperature plays the decisive role. This means the air temperature and humidity. Considering these factors, an air conditioner is (usually) more sensible and not as energy-intensive. It is probably more economical than a reversible air-to-water heat pump while simultaneously dehumidifying, which increases comfort.
If money is not an issue, he should invest it. Usually, we are talking about low four-digit amounts.
An air conditioner (including installation) is more expensive.
Just don’t expect miracles.
I didn’t question the concept but spent a considerable amount of time considering it myself.
It was not discarded for economic or ecological reasons but because we chose a different overall concept. It could not have been integrated effectively here. Radiant floor cooling would not have been an option since my wife always has cold feet anyway.
Air is a poor heat storage medium and heat conductor. However, this applies in both directions.
But the transfer of heat and cold through air is also very slow. Therefore, it is quicker and easier to cool the air itself, which is more important for us as humans. For example, if I cool down the bedroom before going to sleep, it stays cool throughout the night.
At night, the house also releases heat to the outside. As you correctly mentioned, it should be a holistic concept. For example, shading, insulation, controlled ventilation running with an open bypass at night, and so on. This results in additional cooling or less heating. We also pass the air through the ground to cool it further.
Because of this, an air conditioner wouldn’t need to run continuously or would only have to run for shorter periods to achieve the same comfort effect. So the comparison is not irrelevant. A brine-to-water heat pump is more efficient when looking at the theoretical cooling capacity. Even better would be integrating it into the ceiling or walls, resulting in fewer cold feet and a greater effect. Ultimately, the perceived temperature plays the decisive role. This means the air temperature and humidity. Considering these factors, an air conditioner is (usually) more sensible and not as energy-intensive. It is probably more economical than a reversible air-to-water heat pump while simultaneously dehumidifying, which increases comfort.
If money is not an issue, he should invest it. Usually, we are talking about low four-digit amounts.
An air conditioner (including installation) is more expensive.
Just don’t expect miracles.
C
C.beckmann198614 Apr 2020 10:18Many thanks for the numerous and detailed responses; they have been very helpful. I still don’t know which option we will choose, but thankfully, there is still some time. At least now, I don’t have to rely blindly on the heating installer.
K
knalltüte14 Apr 2020 11:23C.beckmann1986 schrieb:
...
Anyway, I no longer have to trust the heating engineer blindly.You should never do that anyway! Whether it’s a heating engineer, electrician, solar technician, etc.
That’s exactly why these great forums exist. Even though some claim that a lot of nonsense is written in forums, they do help to broaden your perspective (wide angle ).
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