ᐅ Controlled ventilation systems vs. exhaust air heat pumps

Hello,
For our KfW70 new build (145m² (1560 sq ft) + 70m² (750 sq ft) basement), we had the first meeting with a heating and ventilation specialist together with the architect. I have basically decided that I want a mechanical ventilation system with heat recovery.

In the first meeting, as with all contractors so far, I asked: What would you do in my position? The answer was: No ventilation system, but rather an exhaust air heat pump. If I understood the system correctly,

• the windows are kept slightly air-permeable (either via ventilation slots in the frame or in the seals)
• exhaust air ducts are installed for wet rooms (bathrooms, kitchen)
• a unit is installed in the basement that draws in air and transfers heat to the domestic hot water through a heat exchanger

So basically a ventilation system that does not recover heat from the air, but instead heats the water, if I may summarize this as a layperson. I was told that this unit including installation is €3,000-4,000 cheaper (offers for both systems will be available in 10 days).

I should also add that a gas boiler is planned and that the property is located in a quiet cul-de-sac (quiet corner...).

Although I have read quite a bit about this online beforehand, the topic is still quite new to me... What do you think about this?

Especially since two rooms in the basement are also to be ventilated...
Thanks in advance – Julius

JGaismayer schrieb:
...For our KfW70 new build, we had the first meeting with a heating and ventilation installer together with the architect. For me, it was already clear that I want a mechanical ventilation system with heat recovery.

That is understandable and reasonable!

JGaismayer schrieb:
...In that first meeting, as with all the craftsmen before, I asked: What would you do in my place? The answer was: No ventilation system, but an exhaust air heat pump.

At this point, I would immediately end all contact with that provider!!!

Best regards

Hi €uro,
do you still have a line for me, and if so, why?

Thanks - J

Hello,

JGaismayer schrieb:
Hi €uro,
do you have one more reason for me, why?

It's quite simple: with a KfW 70 standard, an air-to-water heat pump will almost certainly become a money pit (high operating costs). With a passive house, it would look completely different.

Best regards

Understood – thank you for the explanation!!

€uro schrieb:
Hello,

Relatively simple, because with a KfW 70 standard, an air-water heat pump (AWP) will almost certainly turn into a money pit (high operating costs). It would look quite different with a Passive House, though.

Best regards.

We are planning something similar. Controlled ventilation is decided, but our house will probably be closer to KfW 55 standard.
An initial estimate suggests 40 kWh/m²a (13,000 Btu/ft² per year) and a 5 kW (17,600 BTU/h) heating load for 150 m² (1,615 ft²).
Does an air-water heat pump make sense in this case? Maybe with a pellet heating system, since where else would you get hot water in summer? However, pellet heaters are said to be among the most expensive heating systems.
Our domestic hot water consumption is relatively low, about 20 liters (5 gallons) per day for two people. With a separate apartment, it might be roughly double.
We would prefer to avoid gas, especially since that would require an expensive solar panel installation, which probably wouldn’t be cost-effective for us (see above). Space for a geothermal collector is limited and a borehole will likely not be approved. What about an air-source heat pump?