Is T8 Poroton only significantly better than T12 in heating costs?

According to the U-value calculator and for MY climate zone, a U-value of 0.27 results in a loss of 20 kWh per year and a U-value of 0.19 results in a loss of 14 kWh per year. A difference of 6 kWh over 240m2 amounts to 1,440 kWh per year or, at 7 cents per kWh calculated thermally, it is a difference of 100.80 EUR. An air heat pump with a 20 cent heat pump tariff and an annual performance factor of 3.5 amounts to 5.71 cents per kWh, with the standard tariff of 25 cents and an annual performance factor of 3.5 it is 7.14 cents per kWh.

As a rule, most heat is lost through windows, thermal bridges, and ventilation – I would by no means consider the exterior wall as the decisive factor.

Just for comparison, a window with a U-value of 0.9 (very good!) has a heat loss of 66 kWh per sqm. With 50 m2 of window area, that alone amounts to 3,300 kWh. 240 m2 of masonry with 0.19 come to 3,360 kWh. Ventilation losses with 160 sqm living space and the hygienic minimum air change without controlled residential ventilation with heat recovery are about 5,357 kWh.

All figures are based on my climate zone, as I do not know where you are building. Theoretical values may vary slightly, practical values even more so.

Yes, that's very possible. Assume a heat loss of 20% through the masonry. That gives you 0.2 (20%) * 0.3 (30 worse insulation) = 0.06 --> 6% energy savings. 930 € * 0.94 -> 874 €
7 cents per kWh heating energy is okay - that's the gas price. An annual performance factor of 3 for the air-water heat pump means 0.238 / 3 = 8 cents per kWh heat... so that fits as well.

I told you so :P

Do you mean 240 m² floor area or exterior wall area? At 240 m² floor area, 13 kWh is ambitious... but not impossible either.
Post your energy saving ordinance documents, then many things would be clearer

According to the energy saving ordinance valid next year, the consumption should be around that (maybe a bit less), otherwise it would be too much for approval. I read that it will only be applied for next year?

Oops, just read that the 240m2 are supposed to be the "building area"?? Well, of course, the crucial thing is the masonry area...

And I have to add to my contribution "the calculated consumption" should of course be the term... what is actually consumed then becomes apparent...

Hello everyone,

first of all, thanks for the quick responses from you!

At first glance, it reads as if that is apparently correct. The 240 m² was the floor area. But the indication of the wall area of approx. 260 m² makes more sense. We have also planned a controlled residential ventilation system with heat recovery. A fireplace as well. But rather for the look.

My concern is that the heating costs with an air heat pump could be very high at the end of the year. Hence the idea to insulate a bit better. The additional costs from T12 to T8 are about 6000 euros with our shell builder.

Attached are the thermal insulation certificate and also the heating costs. Had to remove some things so the file wouldn’t be too large. Hope there is still enough information.

Thanks already for your effort and regards,
Tobias

When skimming through: There really was a mistake in there... Heat pump electricity for 7 cents is not known to me at all. Rather calculate with 1600 € heating costs per year. The Energy Saving Ordinance also speaks of 19000 kWh heating energy demand.