ᐅ Exhaust Air Heat Pump vs. Air-to-Water Heat Pump + Photovoltaics: Experiences?

Hello everyone,

We are hopeful to secure a nice plot of land in a nearby town this summer, so we are currently working on concrete house plans. We have decided to build through a general contractor but are still unsure which one to choose. Our shortlist includes Helma and Viebrockhaus. The main difference between these two is their approach to the heating system.

One provider recommends an exhaust air heat pump and currently advises against photovoltaics. The other exclusively installs air-to-water heat pumps combined with a central ventilation system (with heat recovery) and photovoltaics with battery storage.

Since these two recommendations sound completely contradictory to us as laypeople, my wife and I thought you might be able to shed some light on this.

Thank you in advance.

Johannes

Well, those are five completely different things.
In the order you mentioned:
- Exhaust air heat pumps are only suitable for passive houses.
- Photovoltaic systems are always worthwhile; the only exception is deep forests (no sunlight).
- There is generally no issue with air-to-water heat pumps, unless you are building at a high altitude.
- Central ventilation improves living comfort but is unrelated to the heat pump.
- Photovoltaic systems with battery storage make sense only for KfW40+ standards to qualify for subsidies.

Lumpi_LE schrieb:
Well, these are five different things.
In the order you presented:
- Exhaust air heat pump only in passive houses
- Photovoltaics are always worthwhile; only in deep forests (no sunlight) would I advise against it
- Nothing speaks against an air-to-water heat pump, unless you’re building on a high mountain
- Central ventilation improves living comfort but is unrelated to the heat pump
- Photovoltaics with battery storage only make sense for KfW40+ standard to qualify for subsidies

Hello Lumpi,

Yes, I do mix up a lot of things, indeed. But thanks anyway for your quick reply. So for me, that would mean:
Photovoltaics: definitely yes (possibly with battery)
Ventilation: definitely yes (either integrated with the exhaust air heat pump or separate with the air-to-water heat pump)

So, do I understand correctly that the main question comes down to exhaust air heat pump or air-to-water heat pump? Do you have a general recommendation on this? Or do you need more information for such advice?

Best regards,
Johannes

Well, the recommendation was to consider an exhaust air heat pump only in a passive house.

Exactly, in a "true passive house."
KfW40 is not a passive house.
A passive house, among other things, requires 40cm (16 inches) of insulation, south-facing orientation, and so on.

If you are not planning something like this, then do not use an exhaust air heat pump. Also, avoid combined units.

Sorry to ask again, but I need some clarification.
- Even a KfW 40+ house is not considered a Passive House, right?
- Because of that, does an exhaust air heat pump not make sense for other house categories, since the electricity consumption for operation is higher than, for example, with an air-to-water heat pump?
- Is an air-to-water heat pump combined with photovoltaic a sensible concept for a KfW 40+ house with 175 sqm (1882 sq ft)?

Kind regards,

Johannes