ᐅ Ground-source heat pump with or without controlled mechanical ventilation

Hello everyone,
we have received a cost estimate from the architect for a KfW 70 house, including a mechanical ventilation system with heat recovery. When I asked about KfW 55, the architect said that if you go with a ventilation system without heat recovery and add about €8000 (approximately $8,700) extra, then you could have a geothermal heat pump (deep probe). That would probably make KfW 55 achievable. Walls and everything else are planned according to the KfW 55 standard. He said it doesn’t make sense to use heat recovery with geothermal energy because supposedly there are no savings from it. The ventilation would then be €6000 (about $6,500) cheaper. I have to say I’m confused and don’t understand what he means. Can someone explain what he means?

Hi,

I assume you are currently planning an air source heat pump combined with a mechanical ventilation system with heat recovery.

If you replace the air source heat pump with a ground source heat pump using a deep borehole, this system change leads to such a significant increase in heating efficiency that the heat recovery in the mechanical ventilation system is no longer necessary, or the investment in it will not pay off in a reasonable time.

If you can really get a ground heat probe for 8,000 and no longer need to invest 6,000 in heat recovery, you effectively pay 2,000 more and have a system that is 100 times better. That 2,000 will pay off very quickly! The advantages of the deep borehole don’t even need to be listed.

Originally, only gas underfloor heating and a mechanical ventilation system were planned. That’s why I don’t quite understand this. I have another appointment with the architect in January, and I will definitely get to the bottom of it then. I just didn’t want to appear completely uninformed and potentially be able to raise objections.

I actually wanted to know if I could achieve KfW 55 standard with solar thermal systems, and how much extra cost the solar thermal system would involve. He immediately suggested this ground source heat pump under the conditions mentioned above.

What happens to the ventilation when air at -5°C (23°F) is drawn in and blown into the rooms during winter? Besides the increased energy consumption, the comfort level might also need to be discussed.

Where are the comfort differences between the two ventilation systems?