ᐅ Active vs. Passive Air-to-Water Heat Pumps: Differences in Cooling
Created on: 6 Aug 2021 08:44
D
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
R
RotorMotor6 Aug 2021 09:40I still don’t fully understand why you focus so much on the active/passive distinction.
Basically, it means whether the compressor is running (active) or not (passive).
It does not determine whether cooling is possible or not.
Is it only about cooling? As mentioned, cooling is also possible with an air-to-water heat pump, but only actively, not passively.
This results in higher electricity consumption, though with photovoltaic systems that is less of an issue.
With a ground-source (brine-to-water) heat pump, passive operation is possible, meaning without the compressor, because the ground remains cool enough in summer, unlike outside air, which can get very warm in summer.
But yes, it does sound like the refrigerator principle. However, even a refrigerator operates actively.
Basically, it means whether the compressor is running (active) or not (passive).
It does not determine whether cooling is possible or not.
Is it only about cooling? As mentioned, cooling is also possible with an air-to-water heat pump, but only actively, not passively.
This results in higher electricity consumption, though with photovoltaic systems that is less of an issue.
With a ground-source (brine-to-water) heat pump, passive operation is possible, meaning without the compressor, because the ground remains cool enough in summer, unlike outside air, which can get very warm in summer.
But yes, it does sound like the refrigerator principle. However, even a refrigerator operates actively.
H
hampshire6 Aug 2021 09:53Dany250 schrieb:
We would like to manage to keep the temperature in our bedroom on the upper floor below 27°C (81°F) in the future; ideally, between 23°C and 25°C (73°F and 77°F) would be a dream. That is a clear goal. How you achieve it is not only a question of the heat pump technology but also depends on the overall house design, the bedroom’s location, the occupants’ behavior, and so on. Give your building partner as precise requirements as possible in this outcome-focused manner, and then they should propose how to meet them.
Something like this:
“We do not like heat and consider a maximum bedroom temperature of 24°C (75°F) to be a priority for our quality of life. To reach this, we do not want to have to worry about when or which windows or doors are open for convenience. Regarding the bedroom’s location, it is important to us that it does not become a ‘basement cave.’ We are willing to invest more initially in the solution if it helps to reduce energy consumption.”
RotorMotor schrieb:
I still don’t fully understand why you’re so focused on the passive/active distinction.
Basically, it means whether the compressor is running (active) or not (passive).
It doesn’t indicate whether cooling is actually possible or not. I’m trying to express myself more precisely, or rather to use a more suitable, descriptive example.
There is a refrigerator that can cool the temperature down to 0°C (32°F) or lower. Then there is an electric cooler box which can only reduce the temperature by maybe 20°C (36°F) compared to the room temperature.
In this example, I understand the active air-to-water heat pump as the refrigerator and the passive air-to-water heat pump as the electric cooler box.
My hope is that with the active air-to-water heat pump combined with underfloor cooling, a noticeably stronger cooling effect can be achieved than with the passive option.
Is this correct? If so, can such a system, which I prioritize, also lower the temperature during hot summer nights, even when it is not cool enough outside?
@hampshire
I really appreciate your words, but unfortunately in the real world (at least from what you often read) you more frequently encounter people (salespeople, consultants, etc.) who promise everything and take advantage of customers’ lack of experience, as long as they make a sale. Whether it actually turns out that way is another matter, and the salesperson or consultant then wants no further involvement.
That’s why I try, as much as possible, to inform myself in advance and above all to actually understand things. But yes, basically I agree that this should be left to the professionals…
R
RotorMotor6 Aug 2021 10:34Again: as far as I know, there is no passive air-to-water heat pump.
That also doesn’t make sense. How am I supposed to passively cool a house with 30°C (86°F) warm outside air?
The example with coolers is also strange. There are the simple ones with Peltier elements and those with compressors, but even here: both are active!
And an active air-to-water heat pump doesn’t actually cool better than a passive brine-to-water heat pump. Both can only deliver water a few degrees cooler through the floor because otherwise condensation occurs, which then leads to mold.
So, the problem with cooling via the floor is not 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 “real” air conditioning system lies, which inherently removes moisture.
That also doesn’t make sense. How am I supposed to passively cool a house with 30°C (86°F) warm outside air?
The example with coolers is also strange. There are the simple ones with Peltier elements and those with compressors, but even here: both are active!
And an active air-to-water heat pump doesn’t actually cool better than a passive brine-to-water heat pump. Both can only deliver water a few degrees cooler through the floor because otherwise condensation occurs, which then leads to mold.
So, the problem with cooling via the floor is not 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 “real” air conditioning system lies, which inherently removes moisture.
H
hampshire6 Aug 2021 10:35Dany250 schrieb:
Unfortunately, in real life (at least based on what you often read), you more often encounter people (sellers, consultants, etc.) who promise everything and take advantage of customers’ lack of experience, as long as they make a sale. This is exactly why I always recommend not choosing a builder primarily based on price. Always invest in the people and in securing the results – while of course keeping an eye on the costs at the same time.
Of course, any piece of expert knowledge on the topic helps – as long as you are aware of the level of abstraction you are currently exploring, it is very useful. But as soon as you start drawing incorrect or incomplete conclusions from your knowledge, you risk creating unnecessary uncertainty for yourself. Therefore, it is so important to always keep the actual goal in mind, which you apparently can clearly define, unlike many homeowners. Ultimately, you don’t need to care which technology meets your requirements, as long as these requirements are fully defined.
With an air-to-water heat pump in cooling mode, you’ll get a cold floor.
You can also cool the indoor air a bit this way, but it probably won’t lower the temperature by more than a few degrees.
If heat in the bedroom is really such a major problem for you, just install an air conditioner.
It doesn’t cost much for one room, and you can cool down to 24°C (75°F) even when it’s 38°C (100°F) outside if you want.
You can also cool the indoor air a bit this way, but it probably won’t lower the temperature by more than a few degrees.
If heat in the bedroom is really such a major problem for you, just install an air conditioner.
It doesn’t cost much for one room, and you can cool down to 24°C (75°F) even when it’s 38°C (100°F) outside if you want.
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