Prefabricated house heating: Gas / Air heat pump / Underfloor heating

Hi!

We are currently planning a prefabricated house and are torn between Bien-Zenker and Weberhaus. Both strongly promote the air-to-air heat pump from Proxon. However, this is no longer an option for us. The more you inform yourself about it, the less it speaks in favor.

The consideration is now moving towards an air-to-water heat pump (via underfloor heating) with an additional ventilation system or a gas condensing boiler (via underfloor heating), also with an additional ventilation system. For both variants, preparation for a photovoltaic system should be taken into account, which can be purchased later. A geothermal heat pump or a pellet heating system is unfortunately not an option because the investment costs are too high for us.

The structural thermal protection in prefabricated houses is quite good/high. With Bien-Zenker we would build according to KfW70, with Weberhaus even KfW55.

We are now unsure whether we want to invest the additional costs for an air-to-water heat pump (e.g. LWZ 304 from Stiebel Eltron or THZ 304 from Tecalor), or whether a long-established and thus very mature and proven gas condensing boiler could also be a good solution. But how about the ongoing costs for maintenance and upkeep?

The house will be built in Dortmund, has no basement, and will have a living area of 130 to 140 m².

At Weberhaus, an LWZ 304 (with underfloor heating) from Stiebel Eltron currently costs 8,555 EUR as a "jubilee offer" (including ventilation). An offer for a gas condensing boiler is not yet available, unfortunately only the air-to-air heat pump from Proxon, which is not an option anyway. I am somewhat "concerned" about electricity costs in winter and the possible noise of the air-to-water heat pump. Certainly, the gas price as well as the electricity price are rising... however, modern gas condensing units already operate very efficiently and in a well-insulated prefabricated house, heating with gas can also be an affordable solution.

What would you recommend? What else should be considered? How important are maintenance costs in this comparison?

I would be very happy about tips / suggestions and opinions.

Kind regards & thanks!
Gatho

The LWZ is relatively low-maintenance - meaning replace ventilation mats 2-3 times a year and that's it. You can opt for professional maintenance (we currently pay €200 per year) - but it is not mandatory. Many people do it themselves. We run our system with about €65 electricity per month (averaged) for a similar house size. Meaning hot water / heating / ventilation. The LWZ has a relatively small tank - for us the water gets colder for the last person taking a shower (4 people). With a gas heating system, warm water can be supplied on the fly.

We are facing exactly the same problem, the price from Weberhaus is already very good. With Fingerhaus there is the Energy Plus promotion (which already includes underfloor heating, hence the higher price), whereas the Viessmann with outdoor unit is 6,000 € cheaper, which definitely makes you think. Although we would prefer one without an outdoor unit.

Geothermal energy is expensive, but first, there is a €4,500 BAFA bonus, and second, you save on consumption later, even if the insulation is only standard. With an air-to-water heat pump, I would insulate very well because otherwise the heating consumes large amounts of expensive electricity. The benefit of a photovoltaic system, as far as I know, strongly depends on whether the roof has a nice south orientation. If so, it is definitely worth it. A website on the topic of "Heizungsvergleich" by energy consultant Alois Zimmermann, where various heating systems are calculated based on an example house, is recommended. That is my layman’s assessment.

A gas boiler itself should be significantly cheaper than an air-to-water heat pump. But you have to keep in mind: - The gas connection also costs - The chimney also costs - You may have to install solar panels on the roof (hot water or photovoltaics) to meet the primary energy consumption

In the end, this can result in additional costs – or not.

To compare the running costs, you need to look up the gas price and electricity price in your area. Also, the cost for the chimney sweep. Don’t forget the basic fee for the meters!

Furthermore, a gas boiler also requires some electricity and the "annual performance factor" is not quite 1 but 0,... because there are also losses. I would estimate the annual performance factor of the heat pump at around 3 to 3.5, depending on how much you want to invest in the technology.

Have fun calculating.

oh yes: I would always go for underfloor heating or another surface heating. ALWAYS!

Ask DocSchnagels. If I remember correctly, he has had the Tecalor in his Weberhaus in operation for half a year and can definitely say something about it.

Sylvia