ᐅ Heating systems, insulation, government energy efficiency programs, photovoltaic panels – are these components worthwhile?

Hello everyone,

We are planning to build next spring. The building site is south of Bremen in Lower Saxony.

We are going to build a single-family house of 135 m² (1450 ft²). We have received a very detailed quote, and we have a few questions regarding the topics mentioned above.

The house is offered with options such as additional insulation, construction supervision, thermal bridge calculation, under-slab insulation, and a ventilation system. These were described as not necessary or financially neutral. The existing insulation for the exterior walls is 14 cm (5.5 inches), and the roof insulation is 20 cm (8 inches), which is considered sufficient. The ventilation system is also said to be a matter of personal preference.

For heating, we were recommended the Vitocal 200-S (air-to-water heat pump) with 6 kW heating capacity and a 300 L (79 gallons) hot water storage tank. Underfloor heating with individual room control and electric thermostats is planned. Our alternatives were a gas boiler, mainly due to concerns about potential noise from the outdoor unit, and a geothermal heat pump, which was discouraged because our project is too small to justify the investment and the costs of drilling.

We also brought up another air source heat pump option. The builder is willing to install it but would first need to familiarize themselves with the system to confirm they can support it. Maintenance and repair concerns were also mentioned, as technicians might not be familiar with “foreign” systems.

The air source heat pump is now planned to run together with a photovoltaic system, rated at 6 kWp and ready for operation. Installation will be on the side of the roof sloping toward the street, including an inverter and FRE control unit. No battery storage will be installed. Space will be reserved in the utility room for a battery if desired later.

So far, we feel well supported and competently advised. How does this situation sound to more experienced forum users, homeowners, builders, and technicians compared to our perspective?

Thank you in advance and best regards!

The fact that a house needs some kind of heating system is technical detail that a home builder usually wants to handle quickly. Predictability of the solution is part of this. Having a preferred supplier simplifies both the technical side (knowing exactly which system fits each house model) and the commercial side (not least due to bulk purchase conditions).

There are, of course, comparison tests for heat pumps similar to those in car magazines, so customers sometimes want a different model than the standard one. That is not my area of expertise, so you have to decide for yourself how well-founded your choice of the other model really is – for the builder, it simply means more effort at first.

Regarding KfW funding levels, it is probably true that upgrading to something like a “twin-turbo” system does not really bring any “gain” for the homeowner.

If I understand correctly, you only want a different model for the heating system, but not a different concept. I think a different model is fine, but with a different concept I would say it’s best not to push the builder away from what they have routine with – experience can significantly help ensure quality results. That’s why I always advise against trying to “retrain” a builder from Poroton to Ytong or vice versa if you would be the “test case.”

It is better to use a brick that is, according to test results, only 99% optimal but that the builder knows inside out. I see the same logic for heating concepts. If it’s just a different pump manufacturer, I don’t see that as a source of complication.

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Hello,

we completed our house this year, also south of Bremen.

We purchased our own air-to-water heat pump (Panasonic, compact unit 5kW) and had it installed, but at our own risk. With the correct plans, we were able to convince the contractors, which was the biggest challenge. I would definitely choose this heating system again: low complexity – no specialist needed, low initial cost and replacement cost, and efficiency figures even better than expected.

Drilling is not worth it. A horizontal ground heat exchanger (trench collector) is still an option if you have the time and willingness to do some of the installation work yourself.

Careful planning of the underfloor heating is very important. We had it planned externally and paid for it and then presented the ready plans to the contractors. This worked better and avoided unnecessary discussions.

If you are looking for contractors in this region, I am happy to share our experiences via private message.

Skip photovoltaic panels; they are not worthwhile due to the very long payback period. An air-source heat pump is ideal for the size of the house. I would always choose the system that the heating company is familiar with. Experimenting is not recommended in this case.

Photovoltaic systems are economically worthwhile almost always, even when financed with loans.

boxandroof schrieb:
Photovoltaics are almost always economically viable, even with external financing.

Yes; if you climb onto the roof yourself. Otherwise, stocks are economically viable too.