ᐅ Air-to-Air vs. Air-to-Water Heat Pump for a KfW55 House – Importance of Cooling Function
Created on: 26 Jun 2023 14:32
N
nanella
Hello everyone,
we are currently deciding between several prefab house suppliers, and a major difference is the heating system offered. Some suppliers install an air-to-air heat pump as standard (cooling available at extra cost), while others provide an air-to-water heat pump with underfloor heating and a ventilation system with heat recovery (an air conditioning unit can be added). Geothermal or groundwater as a heat source will likely not be an option for the plot we are currently considering. It will be a KFW 55 house, initially without photovoltaics for cost reasons, but solar panels are planned to be added later.
We have already read quite a bit on the topic, but as laypeople, we find it difficult to make a decision regarding the heating system. It is important to know that we are very sensitive to heat and want to include active cooling right from the start. In the worst case, we would need to heat/cool only individual rooms.
These are the advantages and disadvantages we know so far:
In principle, this results in 3 options that we are currently considering (we were advised against underfloor heating with cooling function for the reasons mentioned):
Which option would you prefer, or do you see another solution? Do you have any ideas which option would be better in terms of running costs? Because we probably have a rather expensive plot and need to watch costs during construction, air-to-air currently sounds like the better solution to us.
We would appreciate your assessments.
we are currently deciding between several prefab house suppliers, and a major difference is the heating system offered. Some suppliers install an air-to-air heat pump as standard (cooling available at extra cost), while others provide an air-to-water heat pump with underfloor heating and a ventilation system with heat recovery (an air conditioning unit can be added). Geothermal or groundwater as a heat source will likely not be an option for the plot we are currently considering. It will be a KFW 55 house, initially without photovoltaics for cost reasons, but solar panels are planned to be added later.
We have already read quite a bit on the topic, but as laypeople, we find it difficult to make a decision regarding the heating system. It is important to know that we are very sensitive to heat and want to include active cooling right from the start. In the worst case, we would need to heat/cool only individual rooms.
These are the advantages and disadvantages we know so far:
| Heat Pump | Advantages | Disadvantages |
| Air-to-Air with Cooling Function |
|
|
| Air-to-Water with Underfloor Heating + Air Conditioning |
|
|
| Air-to-Water with Underfloor Heating with Cooling Function |
|
|
In principle, this results in 3 options that we are currently considering (we were advised against underfloor heating with cooling function for the reasons mentioned):
- Install air-to-air heat pump with cooling function
- Install air-to-water with underfloor heating, add air conditioning when photovoltaics are installed, and live with the heat until then
- Install air-to-water with underfloor heating and air conditioning, tolerate high cooling costs until photovoltaics are added
Which option would you prefer, or do you see another solution? Do you have any ideas which option would be better in terms of running costs? Because we probably have a rather expensive plot and need to watch costs during construction, air-to-air currently sounds like the better solution to us.
We would appreciate your assessments.
HeimatBauer schrieb:
If you’re always wearing slippers anyway, where’s the problem? If in doubt, just visit a place like that. We recently had guests over the weekend, and as always, they were absolutely impressed by the cooling. If possible, I would prefer to avoid that in summer. But if the opportunity arises, we will definitely try it out ourselves.
HeimatBauer schrieb:
Strangely, in old buildings, a cold floor feels very chic and cool all year round. Maybe for others, but not for us.
KarstenausNRW schrieb:
Just wondering: how do you think a tiled floor feels in winter with an air-to-air heat pump? THEN you really have a problem. With underfloor heating, the floor feels pleasantly warm underfoot. With an air-to-air heat pump it’s just cold – obviously, it has to be much colder since it’s not heated. In that case, it should at least be natural wood flooring so that not everyone (not just you) ends up with cold feet. Thanks for the tip. We were already aware of that. We would plan to install natural wood floors in most rooms instead of tiles anyway (for aesthetic reasons and because of the heating issue). But yes, in winter, there are many good arguments for underfloor heating. Our concerns were more about cooling in summer. The general opinion here seems quite clear in favor of a water-to-water heat pump, optionally with a cooling function in the underfloor heating system or with air conditioning.
Thank you very much for all the responses; they definitely help us make a decision!
K
KatlarOne27 Jun 2023 13:47Greetings from the post of
Have you planned a central ventilation system?
We are currently leaning towards an air-to-water heat pump with central ventilation (still uncertain if with cooling function) and photovoltaic panels.
HeimatBauer schrieb:
Fundamental decision between air-to-air heat pump and air-to-water heat pump
Have you planned a central ventilation system?
We are currently leaning towards an air-to-water heat pump with central ventilation (still uncertain if with cooling function) and photovoltaic panels.
HeimatBauer schrieb:
I would definitely install proper air conditioning right away. You say that so easily, but if we had unlimited funds, we would have gone straight for photovoltaics plus air conditioning. The cooling function of the heat pump, however, only costs about 500€ (around $540) extra, so that’s the only option we are considering for now.
I will replace the thermostats anyway in the long run because I want to install the smart thermostats from our current apartment. Unfortunately, the general contractor (GC) is somewhat reluctant to install and exclude the other thermostats since they have had bad experiences in the past with client-supplied thermostats (delayed screed drying, defective thermostats, etc.). They want to take full responsibility before we do the final inspection, which I understand and can accept for the time being.
Since I work in IT and would probably call myself a nerd, I am planning to upgrade the entire home automation system myself over the next few years. We were not willing to spend the money upfront, and I enjoy working on this anyway. It has become a bit of a hobby, I would say.
jrth2151 schrieb:
The cooling function of the heat pump only costs about 500€ extraWhere does the 500€ cost come from?Pacmansh schrieb:
Where do the costs of 500€ come from? To be honest, I found that figure here in the forum from an older thread when I was looking into this topic earlier this year. Apparently, you would need some kind of additional valve and moisture sensor, etc. I still need to discuss this with our plumber. It’s on my to-do list for next week.
For me, cooling through underfloor heating systems is neither one thing nor the other. Before building our first house, we looked into it thoroughly because we wanted to take advantage of potential synergies. However, most sources indicate that you cannot exceed a cooling capacity of 2-3°C (4-5°F) with this method.
Our situation is somewhat special due to home office use – but during summer, with two computers running and four monitors, the office temperature can quickly rise above 30°C (86°F) without any cooling. The rest of the house, despite good insulation, also heats up significantly because of the window areas.
It’s common to read opinions here that you have to keep all doors and windows closed during summer. To some extent, I agree – without shading, a newly built house hardly stands a chance. But closing absolutely everything for the entire summer? That’s like living like a hobbit in a cave. To me, quality of living looks very different.
In the end, we combined underfloor heating, an air-to-water heat pump, a central ventilation system, and a proper air conditioning unit. We decided to skip the cooling function of the underfloor heating altogether.
Our situation is somewhat special due to home office use – but during summer, with two computers running and four monitors, the office temperature can quickly rise above 30°C (86°F) without any cooling. The rest of the house, despite good insulation, also heats up significantly because of the window areas.
It’s common to read opinions here that you have to keep all doors and windows closed during summer. To some extent, I agree – without shading, a newly built house hardly stands a chance. But closing absolutely everything for the entire summer? That’s like living like a hobbit in a cave. To me, quality of living looks very different.
In the end, we combined underfloor heating, an air-to-water heat pump, a central ventilation system, and a proper air conditioning unit. We decided to skip the cooling function of the underfloor heating altogether.
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