ᐅ New Gas Heating System for a New Build – Is Solar Thermal Needed for Domestic Hot Water?

Marchonisch schrieb:
Good evening.

Does a new building with a gas heating system really have to include solar thermal (ST) for both domestic hot water and heating support, or is hot water alone sufficient?

We plan to build with solid construction without external wall insulation.

Additionally, we are considering a photovoltaic system. It should be more efficient than solar thermal for heating support, right?

Thank you

The house is being designed by someone—an architect or a construction company. They know that the energy calculation must be submitted with the building permit/planning permission application. They also roughly know: if the house is such and such, the heating system needs to be like this and that; otherwise, it won’t comply.

In our case, when the floor plan was finalized, the general contractor’s manager said: This house requires this type of heating system to meet the energy saving regulations; for KfW 55 standard it would need to be like this and that. You choose, Mr. Client. (Nobody even asked the heating engineer.)

Karsten

Nordlys schrieb:

This was the case here: When our house floor plan was finalized, the head of the general contractor said: This house requires this heating system to meet the energy saving ordinance, and for KfW 55 standards it would need to be like this and that. The choice is yours, Mr. Client.
Karsten

We received an offer and design drawings from our general contractor.
In the first offer, the heating system and central ventilation system were described only in general terms without any specific details.
In the second offer, after my insistence, he at least included the central controlled residential ventilation system with heat recovery (Helios). When I asked why the heating system was still not specified in detail, he said that the calculation and design would only be done with the building permit / planning permission application. We are planning a solid (masonry) single-family house according to the energy saving ordinance.

Overall, we are satisfied with him, although he is not the cheapest (+ about 130€/m² (approx. $140 per square yard) for the same floor plan and comparable scope of work).

Is this kind of approach normal?
At least I would like to know what is planned before signing any contract.

I think he knows more than he admits and wants to keep his options open. Whether Buderus, Junkers, or Brötje? It doesn’t matter if it’s Brötje or someone else. But whether gas or heat pump, he definitely needs to specify that first. Whether underfloor heating or radiators, that also needs clarification.

I think he wants to leave some "flexibility." I specified a gas condensing boiler and underfloor heating throughout the house. For the gas system manufacturer, I prefer Viessmann or Junkers. However, the performance and features of the system are not detailed in the offer, nor is the size of the hot water tank.

However, the energy calculator determined all of this for us first: how many square meters of solar panels, how much water storage capacity, and what heating output. The only fixed components were the solar system, gas condensing boiler, Junkers unit, and underfloor heating. Karsten

When was this decided on your end? It sounds like it happened after signing the contract for work.
It’s possible that the general contractor calculated at the lowest limit. I can’t estimate how high the additional costs might be later for, for example, a better gas system/equipment or a larger hot water tank and, for instance, one made of stainless steel. In my view, solar thermal systems are not planned.