How can the utility room in the basement be effectively integrated into the thermal envelope?

Hello everyone,

we are currently in the planning phase.

It is supposed to be a single-family house with a basement. The ground floor and upper floor are to be built using timber frame construction, the basement either with solid masonry or precast concrete construction (half underground due to sloping site).

The ground floor and upper floor basically meet the KFW 40 standard. Accordingly, a (partial) integration of the basement would probably make sense. Depending on the decision regarding the 52 GW cap, it might also become a 40+ house (ventilation system will be installed in any case).

In the basement, a utility/technical room is planned, the rest of the basement is to be used as a garage. According to the current plan, the heating system will be located in the utility room, so this room must be included in the thermal building envelope.

At present, I see 5 different options to implement this (1-3 could also be built "slimmed down" for KFW 55):

1) Only include the utility room in the thermal envelope

2) Include the entire basement in the thermal envelope (garage door?!)

3) Create a separate, as small as possible room in the basement for the heating system and leave the rest outside the thermal envelope

4) Do without any measures and not use the KFW loan + subsidy

5) Extend the ground floor by a technical room exclusively for the heating system (electricity, ventilation, etc. remain in the basement)

All options naturally differ in costs but also allow for higher subsidies.

We were currently offered a 20cm thick slab in C20/25, the basement level in masonry or concrete, an external wall insulation of the basement with 120mm as well as a screed with 50mm insulation in the utility room. With the note that probably additional insulation measures are necessary (perimeter insulation).

Which route would you take or what is sensible? Is there a better solution that we have overlooked?

Thank you very much and best regards
Noel

The heating system is planned to be placed in the utility room, accordingly the

Are you sure? Our heating system is installed in the unheated basement, which is outside the thermal envelope.

For the plant engineering, one of the six following plant concepts must be implemented. The installation location of the heat generator or the heat transfer station must be within the thermal building envelope and a central domestic hot water preparation must be present. A domestic hot water circulation is permissible.

Interesting. We are "only" renovating and that is not a problem (at least the energy consultant has no objections). I wouldn't have thought that there is a difference compared to new construction, since in the end it's essentially the same (e.g. KfW55).

I am not 100% sure about that either, we have not yet consulted an energy advisor on this.

I only understood it that way from the linked document.

Can someone here confirm or refute this?

I have done some more research. Apparently, "heat generator in thermal envelope" is only required if you want to achieve KFW55 according to reference values (i.e., without exact calculation).

So I am extending my question:

Is it possible to achieve KFW40 without an appropriately insulated basement where the heat generator is located? Or can the prescribed limits be met with such a concept? Has anyone perhaps implemented this themselves?