ᐅ Prefabricated House: Gas Condensing Boiler vs. Air-to-Water Heat Pump – Which Is More Energy Efficient, and What About Consultation?

Hello forum members,

I have been following this forum with great interest and have already learned a lot. Thank you very much!

We are currently planning to build a house and have been going around in circles with our architect for weeks.

It will be a prefabricated house without a basement. The west gable is supposed to have large windows, but energy efficiency is also important to us. Our architect is pushing us towards an air-to-water heat pump but cannot provide a solid justification for it.

She says the following is possible:

KfW 70

• with gas condensing boiler + solar + cross heat exchanger or air-to-water heat pump with heat recovery ventilation and large windows, without slab insulation;

KfW 55

• only with air-to-water heat pump with heat recovery ventilation, partial reduction of window areas, and slab insulation.

So far, I only have the standard offers for the respective technologies, the standard building description, and the building volume.

Now the heating engineer, who is an expert, has called me. Isn’t his interest mainly to steer me towards a high investment?

What documents do I need to hire an independent consultant, and what should I look for when searching for this consultant?

I have heard enough sales pitches in the discussions by now. I would like to base this whole process on data and facts.

Thank you very much for your help!
BS

Hello,

BS_1975 schrieb:
.... Our architect is pushing us toward an air-to-water heat pump but cannot provide solid reasons for it...

She probably isn’t trained for that. It’s surprising that she is taking such a strong stance. If you have an opinion or position, it should be supported with concrete facts and figures => preliminary assessment.

BS_1975 schrieb:
....She says the following are possible:

KfW 70

• with gas condensing boiler + solar + cross heat exchanger or air-to-water heat pump with heat exchanger and large windows without floor slab insulation;

KfW 55

• only with air-to-water heat pump with heat exchanger, partial reduction of window area, and floor slab insulation.

• This should definitely be questioned ;-)

BS_1975 schrieb:
....Now the heating engineer, as an expert, called me. His interest is probably only to push me toward a high investment, right?

Not only that, it also matters how experienced he is with modern technology. However, you can’t simply accuse him of mainly looking out for his own financial interest. He lives in our economic system. With precise planning and dimensioning, you can guide his "scope for design" in the right direction ;-).

BS_1975 schrieb:
....What documents do I need to hire an independent consultant ...

The measured floor plans and sections of all floors as *.pdf files. Also helpful are existing energy saving regulation / KfW certificates as *.pdf or the definition of the proposed building components.

BS_1975 schrieb:
....and what should I look for when searching for this consultant?

Look for independence from sales interests, meaning objectivity. Clarify costs before commissioning.

BS_1975 schrieb:
...I have heard plenty of flowery sales phrases during conversations; I would now like to back everything up with data and facts.

When working freely with an architect, you are not restricted by the conditions of a general contractor (GC) project. Almost all options remain open to find an economically optimal solution.

Best regards

Hello,

When it comes to heating, it is really important to consult an additional specialist alongside the architect. This could be, as you mentioned, a heating engineer or a building services engineer who can provide you with independent advice. If you choose to get advice from a heating engineer, you should definitely obtain several different quotes.

Regarding achieving the energy efficiency classes, you should receive a more detailed explanation than what you have currently been given. Especially if your architect cannot provide solid reasons, you should ask her again about her technical background in building services or whether it might be better to involve a specialist planner for this area.

Providing a statement about your options for achieving the energy efficiency classes without knowing the exact plans and the system is not possible as a remote diagnosis. You really should bring in a specialist if your architect cannot give you clear information.

About the heating engineer: Naturally, they will always keep business considerations in mind, but they will also care about your satisfaction and making sure they get the contract. Therefore, comparing different heating engineers can certainly give you a good overview of the market.

For a building services specialist planner, you will need the plans, and if your architect has already done some calculations related to energy efficiency or energy consumption, you should have those documents as well.

When selecting a specialist planner, you should apply the same criteria you used when choosing your architect. Important factors are definitely their expertise, which you can assess based on references, the costs, the scope of advice and planning offered, and, of course, your overall impression and feeling during your discussions with the specialist planner.

Best regards