ᐅ Active vs. Passive Air-to-Water Heat Pumps: Differences in Cooling
Created on: 6 Aug 2021 08:44
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Dany250
Hello dear community,
First of all, a few words about myself.
We unexpectedly found ourselves back at the topic of building a house due to the very unexpected purchase of a plot of land (we searched for many years and had basically given up on the whole project because of age and the increasingly shorter financing possibilities).
I have been reading quietly and diligently here for the past few weeks, but I still have a question for you and hope you can give me some feedback.
At first, we also considered being convinced by the advertising of some prefabricated house manufacturers and to go with an air-to-air heat pump. However, we have since ruled that out and decided on an air-to-water heat pump instead (I would like to avoid turning this thread into another discussion round about air-to-air heat pumps; I’m not speaking negatively about them, we just decided on the air-to-water heat pump in order to move forward).
We also read that there is a difference between active and passive air-to-water heat pumps. To me, as a complete layperson, it sounds like the active version can be switched to function like a large refrigerator, actively cooling the water in the underfloor heating system. It is said that this variant can cool the climate very well, at least significantly better than the passive option.
We thought we had found our system and wanted to approach prefabricated house manufacturers that offer such a system. However, after reading a lot, you can also find some opposing threads, which is why I wanted to start this thread myself (no situation is the same).
A few words about our situation: We currently live in a multi-family house built in 2014, in the top-floor apartment. Our approximate 90m² (970 sq ft) living space extends almost across the entire attic and includes five skylights that are not shaded from the outside, located under a pyramid roof. To the south, we have a very large roof terrace adorned with a 6m (20 ft) wide window front. The house is situated at about 330 meters (1,080 ft) above sea level in the Stuttgart surrounding area.
During the day, we keep everything closed where possible, but once the heat is inside in summer, we cannot get it out again, meaning we constantly have temperatures above 27°C (81°F) in the bedroom, which simply prevents us from sleeping. A portable air conditioner provides temporary cooling, but already 30 minutes after turning it off, the room returns to the same temperature as before. At night, it is unbearable because it is just too loud.
In other words: we want to do everything better in our new home :-).
The new house is planned to be built with a mono-pitched roof at an elevation of about 300 meters (985 ft), also in the Stuttgart surroundings. The plan is for KfW 40 Plus standard with photovoltaic panels on the roof.
We would like to achieve temperatures below 27°C (81°F) in our upstairs bedroom in the future; ideally between 23°C and 25°C (73°F and 77°F) would be a dream. We are planning a smart home that self-shades with external venetian blinds (also known as louvered blinds). The style will be fairly open, and it will be just the two of us living there. We are thinking about approximately 140 to 150m² (1,500 to 1,615 sq ft) spread over two floors plus a basement (due to practical reasons and the slight slope of the land).
As mentioned before, I have also read that active air-to-water heat pumps don’t work miracles. Could you please tell me if “active air-to-water heat pumps” always mean the type we prefer, specifically with refrigerated water integrated into the floor heating?
Our climate will definitely continue to get warmer, and we plan to live in this house for at least another 30 years. Do you think it would be sensible to equip the house with an air conditioning system from the start? We originally wanted to avoid this and were hoping for cooling via the floor system, but as I said, reading extensively can also cause a lot of uncertainty when making decisions.
We would really appreciate your constructive opinions.
Thank you very much and best regards
Dany
First of all, a few words about myself.
We unexpectedly found ourselves back at the topic of building a house due to the very unexpected purchase of a plot of land (we searched for many years and had basically given up on the whole project because of age and the increasingly shorter financing possibilities).
I have been reading quietly and diligently here for the past few weeks, but I still have a question for you and hope you can give me some feedback.
At first, we also considered being convinced by the advertising of some prefabricated house manufacturers and to go with an air-to-air heat pump. However, we have since ruled that out and decided on an air-to-water heat pump instead (I would like to avoid turning this thread into another discussion round about air-to-air heat pumps; I’m not speaking negatively about them, we just decided on the air-to-water heat pump in order to move forward).
We also read that there is a difference between active and passive air-to-water heat pumps. To me, as a complete layperson, it sounds like the active version can be switched to function like a large refrigerator, actively cooling the water in the underfloor heating system. It is said that this variant can cool the climate very well, at least significantly better than the passive option.
We thought we had found our system and wanted to approach prefabricated house manufacturers that offer such a system. However, after reading a lot, you can also find some opposing threads, which is why I wanted to start this thread myself (no situation is the same).
A few words about our situation: We currently live in a multi-family house built in 2014, in the top-floor apartment. Our approximate 90m² (970 sq ft) living space extends almost across the entire attic and includes five skylights that are not shaded from the outside, located under a pyramid roof. To the south, we have a very large roof terrace adorned with a 6m (20 ft) wide window front. The house is situated at about 330 meters (1,080 ft) above sea level in the Stuttgart surrounding area.
During the day, we keep everything closed where possible, but once the heat is inside in summer, we cannot get it out again, meaning we constantly have temperatures above 27°C (81°F) in the bedroom, which simply prevents us from sleeping. A portable air conditioner provides temporary cooling, but already 30 minutes after turning it off, the room returns to the same temperature as before. At night, it is unbearable because it is just too loud.
In other words: we want to do everything better in our new home :-).
The new house is planned to be built with a mono-pitched roof at an elevation of about 300 meters (985 ft), also in the Stuttgart surroundings. The plan is for KfW 40 Plus standard with photovoltaic panels on the roof.
We would like to achieve temperatures below 27°C (81°F) in our upstairs bedroom in the future; ideally between 23°C and 25°C (73°F and 77°F) would be a dream. We are planning a smart home that self-shades with external venetian blinds (also known as louvered blinds). The style will be fairly open, and it will be just the two of us living there. We are thinking about approximately 140 to 150m² (1,500 to 1,615 sq ft) spread over two floors plus a basement (due to practical reasons and the slight slope of the land).
As mentioned before, I have also read that active air-to-water heat pumps don’t work miracles. Could you please tell me if “active air-to-water heat pumps” always mean the type we prefer, specifically with refrigerated water integrated into the floor heating?
Our climate will definitely continue to get warmer, and we plan to live in this house for at least another 30 years. Do you think it would be sensible to equip the house with an air conditioning system from the start? We originally wanted to avoid this and were hoping for cooling via the floor system, but as I said, reading extensively can also cause a lot of uncertainty when making decisions.
We would really appreciate your constructive opinions.
Thank you very much and best regards
Dany
RotorMotor schrieb:
The example with the coolers is also strange. There are the simple ones with a Peltier element and those with a compressor, but even here: both are active! That’s exactly what the coolers call "Peltier." I never really understood that either 🙂 . Somehow, that thing manages to lower the temperature by about 20°C (36°F) without a compressor. To quote your next sentence again: "How am I supposed to passively cool a house with 30 degrees warm outside air? " I thought passive was the Peltier thing and active was the refrigerator, thanks for the explanation... I think I’ve understood now...
RotorMotor schrieb:
And an active air-to-water heat pump doesn’t really cool better than a passive brine-to-water heat pump. Both can only supply water through the floor that is a few degrees cooler at most, because otherwise condensation occurs and then mold follows.
So the problem with cooling via the floor isn’t due to differences like: active, passive, air-to-water heat pump, brine-to-water heat pump, etc., but condensation!
This is where the big advantage of a “proper” air conditioning system lies, which by design removes moisture. And this is probably where we find the answer to my question...
It might be technically possible, but simply not practical in many cases.
@hampshire
Very, very well written and phrased! You really hit the nail on the head! The "constructed uncertainty" I’ve created for myself is usually my biggest problem! Really excellently described...
@apokolok
I think this is how I will take it and include it in the mix, plan for an auxiliary air conditioning system and use it if needed... I definitely think that’s a better idea than leaving it out and realizing later that it wasn’t sufficient...
Thanks to everyone who has already helped me better understand these things! So thanks to everyone who has contributed here so far...
Cooling with a heat pump means that cold water is circulated through the underfloor heating system. Whether the cold water is generated actively (air-to-water heat pump) or passively (brine-to-water heat pump) doesn’t really matter, and if you have already decided on an air-to-water heat pump, then it is active. However, the effect is the same in both cases: a very moderate reduction of the room temperature by about 2°C (3.6°F). Technically, it is not possible to achieve more than this. If you need greater cooling capacity, using an air conditioning unit is the only option.
In my opinion, house planning should ideally be done so that it can function without air conditioning. To achieve this, it is important to keep heat (especially solar radiation) outside. You are aware of the problem and will take this into account. You have already mentioned external blinds for shading. For south-facing windows, you can work very effectively with roof overhangs and/or building recesses, and the roof can be efficiently protected from overheating by installing a rooftop photovoltaic system (particularly for a shed roof). With a clever combination of these architectural measures, the aforementioned 2°C (3.6°F) cooling through an air-to-water heat pump should be sufficient.
In my opinion, house planning should ideally be done so that it can function without air conditioning. To achieve this, it is important to keep heat (especially solar radiation) outside. You are aware of the problem and will take this into account. You have already mentioned external blinds for shading. For south-facing windows, you can work very effectively with roof overhangs and/or building recesses, and the roof can be efficiently protected from overheating by installing a rooftop photovoltaic system (particularly for a shed roof). With a clever combination of these architectural measures, the aforementioned 2°C (3.6°F) cooling through an air-to-water heat pump should be sufficient.
R
RotorMotor6 Aug 2021 12:55Tempering means both cooling and heating. It is not distinguished from an air conditioning system by function or intensity. As mentioned earlier, the main purpose is dehumidification.
Hangman schrieb:
In my opinion, house design should ideally allow for comfortable living without air conditioning.Respecting your opinion, but there simply isn’t a one-size-fits-all solution. You either design your house to maximize light and heat gain in winter (large south-facing windows, small north-facing windows) or you design it like in Greece, focusing on maximizing cooling in summer. The first approach is primarily used here due to energy saving regulations (building permit / planning permission requirements).
Since we experience both very hot summer weeks and very cold, gloomy winter weeks, it’s impossible to perfectly accommodate both conditions. I don’t find it a big issue to run an air conditioner in the bedroom for a few days or weeks during summer. If you also have a small photovoltaic system on the roof, it can be done relatively climate-neutrally, since the timing of power generation and consumption usually matches quite well in this case.
RotorMotor schrieb:
So this is contradictory. First, it's always said to be passive, and then the correct distinction is mentioned. ;-)Sort of: The house cooling is passive, but the air-to-water heat pump cools actively. However, by now, all clarifications have been made. 😀
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