ᐅ Is the T8 Poroton brick only significantly better than the T12 in terms of 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. The difference of 6 kWh over 240 m2 (2,583 ft2) amounts to 1,440 kWh per year, which, at 7 cents per kWh thermal energy, corresponds to a difference of 100.80 EUR. An air-source heat pump with a 20-cent heat pump tariff and a seasonal performance factor of 3.5 has a cost of 5.71 cents per kWh; with a standard tariff of 25 cents and the same performance factor of 3.5, the cost is 7.14 cents per kWh.

In general, most heat is lost through windows, thermal bridges, and ventilation – so I would not consider the exterior wall as the most critical factor.

For comparison, a window with a U-value of 0.9 (very good!) has a heat loss of 66 kWh per m2 (20,000 BTU per ft2). With 50 m2 (540 ft2) of window area, that amounts to 3,300 kWh. Exterior walls of 240 m2 (2,583 ft2) with a U-value of 0.19 result in about 3,360 kWh. Ventilation losses in a 160 m2 (1,722 ft2) living area with the minimum hygienic air exchange rate without mechanical ventilation with heat recovery are approximately 5,357 kWh.

All figures are related to my climate zone, as I do not know where you are building. Theoretical values may vary slightly; practical values will differ anyway.

BeHaElJa schrieb:
Yes, that’s quite possible. Assume a heat loss of 20% through the masonry. This gives you 0.2 (20%) * 0.3 (30% poorer insulation) = 0.06 → 6% energy savings. €930 * 0.94 → €874
7 cents per kWh of heating energy is okay – that’s the gas price. A seasonal performance factor of 3 for the air-to-water heat pump means 0.238 / 3 = 8 cents per kWh of heat… so that fits as well.

I told you so :P

Do you mean 240 m² (2583 sq ft) floor area or exterior wall area? At 240 m² (2583 sq ft) floor area, 13 kWh per m² is ambitious… but not impossible.
Please post your energy saving regulation documents, that would clarify a lot.

According to the energy saving regulation coming into effect next year, the consumption should be around that level (maybe somewhat less), otherwise it would be too high for a building permit / planning permission. I understand that the application will be submitted only next year?

Oops, I just read that the 240m2 (2583 ft²) is supposed to be the "building area"? Well, the crucial factor is, of course, the masonry surface area...

And I need to add to my post: it should of course say "the calculated consumption"... what is actually consumed will become clear later.

Hello everyone,

First of all, thank you for your quick responses!

At first glance, it seems that this is apparently correct. The 240 m² (2583 sq ft) referred to the floor area. But the wall area of about 260 m² (2799 sq ft) makes more sense. We have also planned a controlled ventilation system with heat recovery. A fireplace as well, but mainly for aesthetic reasons.

My concern is that the heating costs with an air heat pump could end up being quite high by the end of the year. Hence the idea to improve the insulation. The additional cost from T12 to T8 for our shell builder is about 6000 euros.

Attached are the thermal insulation certificate and the heating costs. I had to remove some parts so the file would not be too large. Hopefully, there is still enough information.

Thanks again for your effort and best regards,
Tobias

At a glance: There really is a mistake here... I am not aware of heat pump electricity costing as low as 7 cents.
You should rather expect heating costs of around €1600 (approximately $1700) per year.
The energy saving regulation also refers to a heating demand of 19,000 kWh.