kfw 115 or not - what do you think?

Dear forum,
since 2014 we have been the owners of our semi-detached house from 1962. There is considerable need for renovation; we are now ready to get started. The following measures are planned:
- window replacement, door replacement
- heating system change from central oil-fired stove to gas central heating (condensing boiler including solar thermal)
- roof insulation, re-roofing
- plus renovation of the existing bathroom + installation of a new bathroom in the then converted attic
A lot of work. Overall, this will cost around €180,000. We want to finance it with €25,000 equity, KFW individual measure funding €50,000, bank loan €105,000. That is the plan without external insulation.

For [kfw-Einzelmaßnahmen] we need a certified energy consultant from the expert list. He now recommends the [kfw 115-Haus]: here external insulation (mineral wool) would be added, as well as different windows with a lower U-value. Overall, this means additional costs of about €28,800, according to a quote from a renovation company. Only two of the three walls need to be insulated; the south side is clad with lime panels on the outside, which gives the house a nice 1960s appearance. We would want to keep that anyway; in the [kfw115] variant, lime silicate panels would be applied on the inside here.

Actually, we are in favor of the variant without insulation. I don’t really see the advantages; anyway, I think that if we run into problems with the uninsulated variant after the window replacement, in the worst case we can make adjustments with lime silicate panels. What do you think? Tomorrow the first thing is going to the bank; an [Interhyp] appointment for comparison is also planned. Oh yes: we live in it, since we were tenants before.

Best regards and many thanks for your ideas,
Stefan

Has the energy consultant ever made a calculation of exactly what needs to be done to meet the requirements? It will be difficult to achieve the KfW 115 standard with a gas heating system. I would first have it calculated precisely whether it "pays off," as there is a bit more to fulfill than with the individual measures. If you have worse values in one area, you have to compensate more elsewhere. This will also include insulation against the ground, and if there is an exterior facade cladding that is to remain, should 16 cm of insulation be applied to the wall on the inside? 2-3 cm will not be enough there. We bought an already well-insulated house built in 1976, and everywhere on the ground floor 16 cm had to be added, on the facade upstairs 6 cm (actually 10, but that was simply no longer possible, no roof overhang), floor insulation 10 cm, attic 20 cm, completely new windows and front door, new heating system, etc. And with that, we just barely met the requirements. I would really have the energy consultant run the calculation once in his program.

Hello Elina,

the energy consultant has of course calculated it. He assumes a reduction in primary energy demand from approximately 340 kwh/m2 to 78 kwh/m2. I also did a somewhat rough calculation myself here with the BMWi Sanierungskonfigurator, and that could roughly be correct. The fact is, we have to do something; the 'small' solutions we thought of last year are all not feasible, because if I do something in one place (e.g., heating), I have to start somewhere else as well (in that case, electrical work). Adding insulation would then only be an additional step; according to my calculations, the interest savings through the higher repayment grant possible with [kfw 115] wouldn't be that great anyway. But here I still have to wait for the bank appointment.

The repayment grant has already grown extremely. At that time, we still renovated according to the old guidelines and received 3000 euros, now it would have been 10,500 *cry But the effort to comply with all requirements was considerable. Advantage of the efficiency house compared to individual measures is that personal contribution is allowed.

How big is the house actually and how much did it cost? After all, for 180 k€ you can almost get a small semi-detached house (without land etc.).

Hello,

with attic conversion approximately 140m2 living space, plus 400m2 land. In the location (Greater Stuttgart area, 5 min to the S-Bahn) you would have to find such a property...