ᐅ Reversible air-to-water heat pump vs. air conditioning unit with heating function
Created on: 12 Aug 2020 22:42
H
hendi1908
Hello everyone,
This is my first post here, and when it comes to house building, I am a complete beginner. I will likely have several questions for you in the future regarding the planning and construction of a solid masonry bungalow.
My first question has been on my mind since the beginning of the planning process:
What are your experiences or opinions about a reversible air-to-water heat pump with active cooling compared to an air conditioning system with heating function for the entire house?
I have read many reports on this topic, but every option has its pros and cons. My main concern is which solution is truly the most effective for cooling indoor temperatures during summer when outside temperatures reach around 40°C (104°F), especially with wall thicknesses of 30 to 36.5 cm (12 to 14.5 inches).
I have read that a ground-source (geothermal) heat pump is generally the most efficient, but it is more expensive to install than a reversible air-to-water heat pump. However, based on my experience in the USA (Florida), I am very impressed with an air conditioning system that also provides heating. So, I am uncertain whether a reversible air-to-water heat pump can cool indoor air just as effectively.
A few days ago, during a planning meeting on a day with 39°C (102°F) outside temperature, the representative from my masonry construction company said right away, “You really notice the air conditioning at these temperatures.” That comment surprised me somewhat because everyone usually wants to sell you the KfW construction standard and the most sustainable solution. In my opinion, it won’t help much if, for example, I end up sitting in the bungalow at 30°C (86°F) room temperature when it’s 35°C (95°F) outside, just because I have an air-to-water heat pump.
I would really appreciate any brief replies or shared experiences because practical experience means more to me than any reports or sales pitches promoting the latest technology.
Best regards
This is my first post here, and when it comes to house building, I am a complete beginner. I will likely have several questions for you in the future regarding the planning and construction of a solid masonry bungalow.
My first question has been on my mind since the beginning of the planning process:
What are your experiences or opinions about a reversible air-to-water heat pump with active cooling compared to an air conditioning system with heating function for the entire house?
I have read many reports on this topic, but every option has its pros and cons. My main concern is which solution is truly the most effective for cooling indoor temperatures during summer when outside temperatures reach around 40°C (104°F), especially with wall thicknesses of 30 to 36.5 cm (12 to 14.5 inches).
I have read that a ground-source (geothermal) heat pump is generally the most efficient, but it is more expensive to install than a reversible air-to-water heat pump. However, based on my experience in the USA (Florida), I am very impressed with an air conditioning system that also provides heating. So, I am uncertain whether a reversible air-to-water heat pump can cool indoor air just as effectively.
A few days ago, during a planning meeting on a day with 39°C (102°F) outside temperature, the representative from my masonry construction company said right away, “You really notice the air conditioning at these temperatures.” That comment surprised me somewhat because everyone usually wants to sell you the KfW construction standard and the most sustainable solution. In my opinion, it won’t help much if, for example, I end up sitting in the bungalow at 30°C (86°F) room temperature when it’s 35°C (95°F) outside, just because I have an air-to-water heat pump.
I would really appreciate any brief replies or shared experiences because practical experience means more to me than any reports or sales pitches promoting the latest technology.
Best regards
What are the basic specifications of your house, especially the insulation standard?
This topic is very individual, also because everyone has a completely different perception of heat or temperatures.
Some people are bothered by a slight draft, others by the noise of a mechanical ventilation system, and others by the too-cool air from the air conditioning, among other things. A single opinion won’t really help you here; there are always many options, and you can learn to live with them. However, each solution has its own characteristics as well as advantages and disadvantages, which you ultimately have to weigh for yourself. Therefore, more input is needed first about what is important to you, what you like and don’t like, or what your current thoughts are for or against something.
This topic is very individual, also because everyone has a completely different perception of heat or temperatures.
Some people are bothered by a slight draft, others by the noise of a mechanical ventilation system, and others by the too-cool air from the air conditioning, among other things. A single opinion won’t really help you here; there are always many options, and you can learn to live with them. However, each solution has its own characteristics as well as advantages and disadvantages, which you ultimately have to weigh for yourself. Therefore, more input is needed first about what is important to you, what you like and don’t like, or what your current thoughts are for or against something.
U
UnfähigerBeamt30 Apr 2025 09:05@Arauki11 The insulation standard is between KfW 40 and 55. Timber frame construction. It is indeed very customizable, but I’m trying to navigate through the complexity a bit. The feeling of cold or warmth is one thing, but I can assess that well. That’s why I try to keep the questions as general as possible: namely, whether you will feel a draft? I have heard about so-called “wind free” systems. Maybe there is some experience with this specifically.
What is important to us:
- Climate control. Cooling by 2-4 degrees is not sufficient.
- Also, we don’t want cold feet (e.g. from the cooling function of an air/water heat pump)
- Warm air is generally perceived as pleasant; we have never had underfloor heating before, so it’s not “missed” per se.
What we absolutely don’t want:
- Sitting on the sofa and feeling a draft (whether heating or cooling)
Possible issue:
- The living and dining area is about 50 sqm (540 sq ft). Possibly a more powerful unit is needed for this space, which – logically – would cause a stronger airflow. (or alternatively, using two units in the large room)
Cost question:
We have two offers. One is a classic underfloor heating plus ventilation system costing 62,000 EUR; the other is an air/water heat pump with ceiling cassettes at 40,000 EUR.
Huge difference for – logically – the exact same building.
What is important to us:
- Climate control. Cooling by 2-4 degrees is not sufficient.
- Also, we don’t want cold feet (e.g. from the cooling function of an air/water heat pump)
- Warm air is generally perceived as pleasant; we have never had underfloor heating before, so it’s not “missed” per se.
What we absolutely don’t want:
- Sitting on the sofa and feeling a draft (whether heating or cooling)
Possible issue:
- The living and dining area is about 50 sqm (540 sq ft). Possibly a more powerful unit is needed for this space, which – logically – would cause a stronger airflow. (or alternatively, using two units in the large room)
Cost question:
We have two offers. One is a classic underfloor heating plus ventilation system costing 62,000 EUR; the other is an air/water heat pump with ceiling cassettes at 40,000 EUR.
Huge difference for – logically – the exact same building.
N
nordanney30 Apr 2025 09:33UnfähigerBeamt schrieb:
Big difference for – logically – exactly the same building. But completely different technology. A well-designed controlled residential ventilation system, which for example does not have the air outlet directly above the sofa, you will not feel, or only when you activate party mode.
Climate = draft. You won’t be able to avoid this, as it’s simply the nature of this type of heating. Warm (or cold) air has to be blown into the room.
Underfloor heating and controlled residential ventilation = with correct design, no noticeable effect (except fresh air and a warm room), but no cooling function as you want.
What you want as an all-in-one solution can at best be achieved by building component activation = concrete core activation. Strong cooling will typically always result in some air movement.
I am basically interested in this topic as well.
I would appreciate a correction of my thoughts (or possibly agreement – although I’m not very optimistic about that):
- Ventilation systems have almost become a quasi-standard in new buildings nowadays. Couldn’t I use an air-to-air heat pump here to both cool and heat, and make use of the existing infrastructure (or, if the duct cross-sections are too small, adapt the infrastructure inexpensively while still in the planning phase)? Or am I too far from having suitable infrastructure for cooling/heating, making this simply impractical?
- I could even retrofit this air-to-air heat pump later if I’m hesitant to invest at first and want to see if it’s possible to manage without it, assuming shading is well designed and the house has enough thermal mass to avoid strong overheating, plus a slight cooling effect through ventilation and a night bypass.
- Since I will need water heating anyway with an air-to-air heat pump, I was thinking about an air-to-water heat pump instead. My idea was a very minimally sized air-to-water heat pump combined with underfloor heating, which could additionally support cooling in the summer, handle water heating, and provide most of the heating function in winter.
So basically, a standard system initially with ventilation and an air-to-water heat pump (including underfloor heating), which I could possibly expand quickly and affordably with an air-to-air heat pump if needed.
I would appreciate a correction of my thoughts (or possibly agreement – although I’m not very optimistic about that):
- Ventilation systems have almost become a quasi-standard in new buildings nowadays. Couldn’t I use an air-to-air heat pump here to both cool and heat, and make use of the existing infrastructure (or, if the duct cross-sections are too small, adapt the infrastructure inexpensively while still in the planning phase)? Or am I too far from having suitable infrastructure for cooling/heating, making this simply impractical?
- I could even retrofit this air-to-air heat pump later if I’m hesitant to invest at first and want to see if it’s possible to manage without it, assuming shading is well designed and the house has enough thermal mass to avoid strong overheating, plus a slight cooling effect through ventilation and a night bypass.
- Since I will need water heating anyway with an air-to-air heat pump, I was thinking about an air-to-water heat pump instead. My idea was a very minimally sized air-to-water heat pump combined with underfloor heating, which could additionally support cooling in the summer, handle water heating, and provide most of the heating function in winter.
So basically, a standard system initially with ventilation and an air-to-water heat pump (including underfloor heating), which I could possibly expand quickly and affordably with an air-to-air heat pump if needed.
N
nordanney30 Apr 2025 10:13Sahitaz schrieb:
- Ventilation systems have become almost a standard feature in new buildings nowadays. Can I use an air-to-air heat pump here to provide additional cooling/heating and utilize the existing infrastructure (or, if the duct cross-sections are too small, adjust the infrastructure affordably while still in the planning phase), or is the available infrastructure for cooling/heating so unsuitable that it simply isn’t practical?Ventilation and heating are different technologies. Not every room in a mechanical ventilation with heat recovery system (MVHR) simultaneously receives exhaust and supply air. So, the airflows don’t align properly. Additionally, the volume flows differ.There are now add-ons available for MVHR systems, for example with about 2.5 kW (8,500 BTU/h) cooling capacity – but these come at a cost and require a suitably designed MVHR system (insulated ductwork, minimum volume flow, etc.).
Sahitaz schrieb:
- I could even retrofit this air-to-air heat pump later if I want to avoid the initial investment and first see whether I can manage without it, assuming the shading is well planned and there is enough thermal mass in the building to prevent strong overheating (+ slight cooling effect from ventilation and bypass at night)See the first answer.Sahitaz schrieb:
- Since I need water heating anyway if I use an air-to-air heat pump, I was thinking of an air-to-water heat pump. I was considering a very modestly sized air-to-water heat pump with underfloor heating that could also somewhat support cooling in summer, handle water heating, and provide most of the heating function in winter.If you’re heating with an air-to-air heat pump, you still need a separate water heater. I understand the second part of your comment as wanting to install basically two heating systems. That would be like a car with both a gasoline and a diesel engine that can run alternately.Thanks already for the reply! That’s more than a steep price :O
Yes, the question is whether the rooms with supply air are also the ones I want to cool? I would say, for the most part, yes.
That’s why I see this more as a minor issue, because the living and common areas are usually supplied with fresh air (I had even thought about this, just didn’t write it down – but definitely a valid point and maybe not as relevant for everyone as it is for me).
Insulated ducts is a very good point! Thanks.
Then the question is what volume flow rates achieve how much cooling capacity, or in plain terms, ‘how much cooling can I get from the volume flows that I can reasonably use in the controlled residential ventilation system?’
The last point is more like ‘I want the air-to-water heat pump because it’s the basis of the house; if I have the air-to-air heat pump, I could use it additionally to relieve the air-to-water heat pump or to operate it more efficiently.’
So it’s more comparable to a hybrid system – although I’m actually not a fan of hybrid cars at all.
Yes, the question is whether the rooms with supply air are also the ones I want to cool? I would say, for the most part, yes.
That’s why I see this more as a minor issue, because the living and common areas are usually supplied with fresh air (I had even thought about this, just didn’t write it down – but definitely a valid point and maybe not as relevant for everyone as it is for me).
Insulated ducts is a very good point! Thanks.
Then the question is what volume flow rates achieve how much cooling capacity, or in plain terms, ‘how much cooling can I get from the volume flows that I can reasonably use in the controlled residential ventilation system?’
The last point is more like ‘I want the air-to-water heat pump because it’s the basis of the house; if I have the air-to-air heat pump, I could use it additionally to relieve the air-to-water heat pump or to operate it more efficiently.’
So it’s more comparable to a hybrid system – although I’m actually not a fan of hybrid cars at all.
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