ᐅ Fresh Air Heating vs. Air-to-Water Heat Pump Installed Indoors – Alternatives?
Created on: 21 Mar 2022 12:31
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FlitzerHello everyone,
We are currently planning a new house. Unfortunately, according to the local development plan, the outdoor installation of an air-to-water heat pump is not allowed. Personally, I find an indoor installation unappealing at the moment (space in the technical room, large holes in the wall, noise(?)), but I’m open to being convinced otherwise.
We have now received initial offers for a fresh air heating system (air-to-air heat pump), which I find quite attractive due to the filtering and cooling functions, allowing us to sleep with closed windows in summer (highway within sight, no speed limit, <<1km (0.6 miles)).
Unfortunately, I have not found much positive information online about such a fresh air heating system (and only few well-founded negatives…). At least not when the outdoor installation of an air-to-water heat pump with underfloor heating is off the table. Also, so far no provider has addressed my inquiry regarding a horizontal ground collector (because it’s expensive).
Fossil fuels are out of the question, electricity would come from the solar panels on the roof (possibly with storage).
1) Has anyone had good experience with a fresh air heating system (ceiling diffusers)? --> Bathroom planned with infrared ceiling panels
2) What would be a reasonable alternative?
3) Is an integrated installation of an air-to-water heat pump really as unattractive as the house builders suggest? --> They tend to tell you only what benefits them, and in the prefab house sector, "ventilation is the best invention since beer," as they say ;-)
By the way, KFW-55 standard, optionally KFW-40, no basement, about 150m² (1,615 sq ft) living area with a pitched roof. Funding is secondary for now.
Thanks
Flitzer
We are currently planning a new house. Unfortunately, according to the local development plan, the outdoor installation of an air-to-water heat pump is not allowed. Personally, I find an indoor installation unappealing at the moment (space in the technical room, large holes in the wall, noise(?)), but I’m open to being convinced otherwise.
We have now received initial offers for a fresh air heating system (air-to-air heat pump), which I find quite attractive due to the filtering and cooling functions, allowing us to sleep with closed windows in summer (highway within sight, no speed limit, <<1km (0.6 miles)).
Unfortunately, I have not found much positive information online about such a fresh air heating system (and only few well-founded negatives…). At least not when the outdoor installation of an air-to-water heat pump with underfloor heating is off the table. Also, so far no provider has addressed my inquiry regarding a horizontal ground collector (because it’s expensive).
Fossil fuels are out of the question, electricity would come from the solar panels on the roof (possibly with storage).
1) Has anyone had good experience with a fresh air heating system (ceiling diffusers)? --> Bathroom planned with infrared ceiling panels
2) What would be a reasonable alternative?
3) Is an integrated installation of an air-to-water heat pump really as unattractive as the house builders suggest? --> They tend to tell you only what benefits them, and in the prefab house sector, "ventilation is the best invention since beer," as they say ;-)
By the way, KFW-55 standard, optionally KFW-40, no basement, about 150m² (1,615 sq ft) living area with a pitched roof. Funding is secondary for now.
Thanks
Flitzer
B
Benutzer20021 Mar 2022 12:55Flitzer schrieb:
1) Has anyone had good experience with a fresh air heating system (ceiling diffusers)? --> Bathroom planned with infrared elements in the ceiling Only at work – KfW 55 standard makes it a no-go. Advantage: dirt cheap compared to a conventional heating system. But most of the costs come from operation...
Flitzer schrieb:
2) What would be a sensible alternative? Brine-water heat pump. A trench collector is the classic perfect area for do-it-yourself work. Or the shell builder digs the trenches directly in the garden in exchange for a box of beer. No additional costs. Also none for the contractor.
Flitzer schrieb:
3) Is an integrated installation of the air-water heat pump really as unattractive as builders make us believe? Complete nonsense. It’s a common (though not very frequent) option.
Flitzer schrieb:
They only tell you what benefits them, and that would be for prefab houses that "ventilation is the best thing since beer was invented" ;-) Of course, air-to-air heat pumps have an advantage – for the contractor. They save the expensive heating system with underfloor heating and install a blower heater instead. But they charge well for that...
The indoor heat pump can be installed anywhere, even in the attic if available. Of course, it produces noticeable noise, but that can be easily managed with construction measures.
Hello user 200 😎
Thanks for your detailed reply.
Why is ventilation considered a no-go for a KFW55 house? Is the thermal insulation insufficient? Or under what conditions would it work?
Besides electricity consumption, what are the realistic arguments against an air-to-air heat pump with heat recovery? Can they not reach the required temperature levels, do they have hygiene issues, do they use too much electricity, or are they just not reliable? I’m just trying to understand why everyone is against it except those who sell it. If I already have a solar system on the roof, heating with electricity isn’t a problem; at night it’s switched off anyway, and in winter air-to-water heat pumps also consume a lot of electricity.
I also pictured the trench collector quite naively (just quickly dig a hole nearby, insert the pipe, done)... but everyone seems hesitant when I bring it up in conversations, so I’ll need to follow up on that... Doing the work myself within the trades is difficult because of warranty issues and it’s not even that cheap if you have to rent the excavator. --> unless the excavator operator spontaneously helps out with the foundation work --> but then construction management and the builder are involved and both take responsibility.
The heat pump in the attic would be an option I only considered briefly... but then you still have the noisy unit inside the house, above the bedrooms...
Best regards, Flitzer
Thanks for your detailed reply.
Why is ventilation considered a no-go for a KFW55 house? Is the thermal insulation insufficient? Or under what conditions would it work?
Besides electricity consumption, what are the realistic arguments against an air-to-air heat pump with heat recovery? Can they not reach the required temperature levels, do they have hygiene issues, do they use too much electricity, or are they just not reliable? I’m just trying to understand why everyone is against it except those who sell it. If I already have a solar system on the roof, heating with electricity isn’t a problem; at night it’s switched off anyway, and in winter air-to-water heat pumps also consume a lot of electricity.
I also pictured the trench collector quite naively (just quickly dig a hole nearby, insert the pipe, done)... but everyone seems hesitant when I bring it up in conversations, so I’ll need to follow up on that... Doing the work myself within the trades is difficult because of warranty issues and it’s not even that cheap if you have to rent the excavator. --> unless the excavator operator spontaneously helps out with the foundation work --> but then construction management and the builder are involved and both take responsibility.
The heat pump in the attic would be an option I only considered briefly... but then you still have the noisy unit inside the house, above the bedrooms...
Best regards, Flitzer
W
WilderSueden21 Mar 2022 15:10Ultimately, this is an electric direct heating system integrated into the ventilation. So, 1 kWh of electricity equals 1 kWh of heat. It is a very expensive way to heat, considering you have an estimated heating demand of 5000 kWh, which results in heating costs of 2000–2500 euros. For a new build, this is definitely not appropriate.
Just try using a major search engine. And don’t click on results from manufacturers of these devices.
It would be helpful if you familiarize yourself with some basics to understand this better.
In principle, you need to understand that an air-to-air heat pump is not a conventional heat pump. It does not convert energy from an external source like air, water, or ground loop into heating energy. Instead, it uses the energy from the house’s exhaust air and tries to transfer as much of that as possible back into the fresh (cold) outside air to warm it up. However, you can only recover what is there. There are losses involved—otherwise, it would be a perpetual motion machine. These losses need to be compensated. For this, the supplied air is preheated and/or reheated using electricity. Unlike heat pumps that operate at a ratio of about 1:3 to 1:5, this is roughly 1:1 (I’m not an expert on this, but this is just to illustrate the point).
This principle works in a passive house because it is so well insulated that there are hardly any losses. These losses are balanced by solar and internal gains, and if some additional heating is needed, it doesn’t have much impact. On the other hand, you save on a lot of technical equipment, such as underfloor heating. In an average KfW55-standard house, however, losses are too high. You won’t be happy with the system, especially with rising electricity costs.
And forget about photovoltaics. That’s a nice additional effect and makes sense, but when you need the most energy—typically in winter—you get little to no output. And no, the heating system is not turned off at night. Night setback usually doesn’t make sense in a modern house.
It would be helpful if you familiarize yourself with some basics to understand this better.
In principle, you need to understand that an air-to-air heat pump is not a conventional heat pump. It does not convert energy from an external source like air, water, or ground loop into heating energy. Instead, it uses the energy from the house’s exhaust air and tries to transfer as much of that as possible back into the fresh (cold) outside air to warm it up. However, you can only recover what is there. There are losses involved—otherwise, it would be a perpetual motion machine. These losses need to be compensated. For this, the supplied air is preheated and/or reheated using electricity. Unlike heat pumps that operate at a ratio of about 1:3 to 1:5, this is roughly 1:1 (I’m not an expert on this, but this is just to illustrate the point).
This principle works in a passive house because it is so well insulated that there are hardly any losses. These losses are balanced by solar and internal gains, and if some additional heating is needed, it doesn’t have much impact. On the other hand, you save on a lot of technical equipment, such as underfloor heating. In an average KfW55-standard house, however, losses are too high. You won’t be happy with the system, especially with rising electricity costs.
And forget about photovoltaics. That’s a nice additional effect and makes sense, but when you need the most energy—typically in winter—you get little to no output. And no, the heating system is not turned off at night. Night setback usually doesn’t make sense in a modern house.
We have an air-to-water heat pump installed indoors.
There is one supply air and one exhaust air vent with covers on the exterior wall. So, no large unsightly holes. I find this more attractive than having the units placed somewhere in the garden.
Noise
Hot water production and defrosting are somewhat louder. In everyday life, it’s barely noticeable; when it’s quiet, you can clearly hear it. Normal heating operation is really very quiet.
With a fresh air heating system near a highway, I would be more concerned—not only about the high heating costs but also about noise coming into every room through the vents.
There is one supply air and one exhaust air vent with covers on the exterior wall. So, no large unsightly holes. I find this more attractive than having the units placed somewhere in the garden.
Noise
Hot water production and defrosting are somewhat louder. In everyday life, it’s barely noticeable; when it’s quiet, you can clearly hear it. Normal heating operation is really very quiet.
With a fresh air heating system near a highway, I would be more concerned—not only about the high heating costs but also about noise coming into every room through the vents.
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