ᐅ Waste Heat Heat Pump vs. Ground Source Heat Pump

Dear forum members,

As part of our search for the right builder, we are concerned, among other things, about choosing the "right" or most suitable energy concept for our KfW55 / KfW40 house.

Our top choices are a ground source heat pump and an exhaust air heat pump. We generally lean towards a ground source heat pump due to the well-known advantages frequently mentioned online. Since houses are increasingly well insulated and almost "airtight," we are also considering installing a central ventilation system with heat recovery.

Now the second option comes into play: the exhaust air heat pump. I have already read quite a bit about this online, but it has not necessarily convinced me. To put it simply:
- I am concerned that the system is so sensitive that when windows are opened (e.g., for a short airing), the system will need to draw significantly more energy from the electric heater.
- The same applies on cold days, which could lead to unpleasant drafts caused by cold air flowing in.
- I have also read that a cycle can occur if the system has to provide energy to heat the hot water tank by taking heat from the ambient air. Fresh air must then automatically flow in, which again needs to be heated to the desired room temperature. I’m not an energy expert, but there seems to be a catch here.
- What about summer and opening the patio doors? How does the system behave in that case?

As I said, I am just a layperson and find the topic of exhaust air heat pumps challenging. Do you have any experience with them? Which system (ground source vs. exhaust air heat pump) would you recommend from your perspective?

Thank you—we appreciate any advice.

Good luck
Olgus

I would choose a ground source heat pump. It is a reliable technology. The problem lies with domestic hot water for air source heat pumps, especially when dealing with exhaust heat. A lot of cooling needs to be removed or heat supplied. Especially above 40°C (104°F), the pump also loses efficiency and then a large volume of air is needed to compensate.

Olgus2016 schrieb:

The geothermal heat pump and an exhaust air heat pump are the top options.

I’m with you on the exhaust air heat pump, but why are you interested in a ground source heat pump when building a simple single-family house? Any advantages?

Regards, Bauexperte

In the end, it comes down to the price and the choice of the general planner / general contractor – what will the brine-to-water heat pump plus central controlled ventilation system cost you compared to the exhaust air heat pump? What does your preferred general planner / general contractor offer? What are they capable of?

You won’t resort to supplementary heating with either option – especially if you are aiming for KfW40 standard.

What about a third alternative: an air-to-water heat pump?

Hello everyone, and thank you for the feedback at this late hour. Yes, indeed, an air-to-water heat pump is also an option, but I tend to be discouraged by the following aspects:

- lower efficiency compared to a ground-source (geothermal) heat pump, although I have read that they are now roughly equal
- durability compared to the ground-source heat pump
- maintenance requirements
- noise disturbance

The apparent disadvantages are actually advantages of the ground-source heat pump ... at least according to my layman’s understanding ... plus there is the BAFA subsidy on top. Why wouldn’t a ground-source heat pump be considered for a single-family home? Have I overlooked something important?

Thank you all

It’s just expensive to purchase – even after deducting the 4,500 € (4,500 euros) ;-) You should also check whether drilling is allowed – alternatively, trench collectors can be used; however, these naturally require a lot of space.