Construction costs kfw70 vs. kfw55 vs. kfw40

Hello,

I am currently also in the planning phase, but with a timber frame house with a granny flat, meaning 2 residential units. Standard was offered as KFW55 (air-water heat pump), additional costs for KFW40 €6200 according to the offer with an additional subsidy of €10,000, so I don't need to calculate any further. I will probably even go through with KfW 40 +

... Additional costs KFW40 €6200 according to the offer with an additional funding of €10,000, so I don't need to calculate any further.

Can you provide a few more details on how the €6,200 is composed? Thanks.

As already mentioned, the house is designed as KFW55, anything else no longer makes sense to me. According to my planner, gas would not have made sense here anyway, so it’s air-water heat pump right away (with photovoltaics as KFW40+ in the background, everything somehow fits together). Of course, the question then arose what it takes to go from KFW55 to 40 and also to 40+, according to the offer it is now 3200 for the insulation of the walls and ceiling (flat roof) + 3000 for insulation under the basement floor slab. I should also mention that the final calculation is still missing, but according to the estimate by the energy consultant, it should work out.

I am currently also waiting for the calculation. However, monolithic (brick)

We only have one residential unit, but would still receive 4500€+8000€ through the 10,000 houses program.

Can one actually say that at least a certain brick is needed to achieve KFW55 (e.g. T8)?

For us, a 36.5 cm brick with WDZ 0.08 is needed. With that, we achieve a U-value of 0.21 W/m²K. The critical point for us was the basement wall, which we cannot insulate as thickly as we want because of the required bearing area for the 36.5 cm brick (or because we did not want an overhanging edge of insulating material at the ground floor base). Therefore, 12 cm of Styrodur was the maximum here, resulting in a U-value of 0.32 W/m²K. However, we will probably add another 4 cm in the ground, i.e., in a later invisible area, because the basement will be partially occupied and it certainly doesn’t hurt.

So, we are not doing it now. The thicker wall construction would eat up too much living space, and since the start of construction is already quite close, getting the approval would be too stressful. Otherwise, we would end up with a four-digit amount, from KfW 55 to 40+.