Energy saving through better stones

Hello everyone,

I had not found any calculation whether better insulated bricks are really worthwhile, so I calculated it myself at Ubakus:

House data: floor area 10m x 9.5m; room height 2.5m; location Munich (cold region), wall area: 221 m²

Energy loss of the wall with the following U-values:
U=0.23 = 4135 W/a
U=0.21 = 3809 W/a
U=0.18 = 3320 W/a
U=0.17 = 3163 W/a

Assuming a heat pump with an annual performance factor = 4, electricity price = €0.27, the following energy cost differences result compared to the worst bricks (0.23):

0.23 = -
0.21 = €22 /a; €880 / 40 years
0.18 = €55 /a; €2200 / 40 years
0.17 = €65 /a; €2620 / 40 years

Example bricks: Poroton Wienerberger List prices36.5
Required bricks: 3500 pieces

0.23 = €5.6 per piece
0.21 = €6 per piece; total surcharge: €2100
0.18 = €6.3 per piece; total surcharge: €2450
0.17 = €6.7 per piece; total surcharge: €3850

So somehow I don’t see a significant advantage in using better bricks. Especially if you live in a warmer region.

yes, not at all worth it. It's pure money burning

Requirement: electricity prices do not rise faster than the interest you pay on the additional costs. Then, depending on the case, the breakeven point will come.

And: If you only break through the KFW-55 threshold with another brick, money will rain down

I don't believe that outweighs the additional cost, but a possible advantage could be that smaller heat pumps are feasible, lower supply temperatures are possible (better annual performance factor), and thereby possibly qualify for BAFA funding. I think it's a very individual matter. Simply saying that better insulation brings the savings currently won't be worthwhile.

Requirement: electricity prices do not rise faster than the interest you pay on the additional costs. Then, depending on the situation, the breakeven point will come.

And: If you only break through the KfW-55 threshold with a different brick, money will rain

Since 24.01.2020 this is true

I don’t really believe it offsets the surcharge, but a possible advantage could be a smaller heat pump, lower supply temperatures possible (better annual performance factor) and thus possibly achieving BAFA funding. I think it’s a very individual matter. Just saying better insulation brings the savings will currently not pay off.

The problem is that there are hardly any heat pumps with such low capacity.
For my house, 4-5 kW with 0.21 bricks are already enough.
Unfortunately, heat pumps are often oversized out of ignorance.

But I also agree with you that it always has to be considered individually, but the trend is towards being unprofitable.

And: If you manage to break the KfW-55 threshold with just another stone, money will rain down

You mean the repayment from KfW for the 100,000 loan, right?