ᐅ Wall U-value 0.26 – Is that acceptable?

jumi1 schrieb:
I think the calculation is a bit too simplified and not accurate. You’re going to worsen the U-value by almost 20%! I consider a U-value of 0.26 for a new building to be very poor.

Simplified? Of course. I didn’t perform a daily heat loss calculation, and the impact on the north side or in windy conditions is certainly greater than on the south side, but on average, depending on the region and location, you’ll end up around 60-80 kWh per U-value change of 1 W/m²K if the material is the same, just thicker or thinner.

The 20% sounds more dramatic than it really is. Heat transfer through the walls accounts for about one-fifth of the total demand – so that’s only around a 4% increase in energy consumption. That can be offset by better windows or roof insulation, or by proper detailing of thermal bridges and maintaining high airtightness without shortcuts.

However, I don’t see much benefit in higher sound insulation here either. Again, connections and windows remain the weak points.

Bauherr&-Frau schrieb:

Hello everyone,

We have now been offered the PP4 0.5 (also 36.5 cm (14.4 inches)) instead of the Ytong PP2 0.35 (36.5 cm (14.4 inches)) for better sound insulation. The PP2 has a thermal conductivity (λ) of 0.08 (U-value 0.21), and the PP4 has a λ of 0.10 (U-value 0.26). We are attracted by the improved soundproofing, but is the increase in heat loss too high? The windows have a Ug of 0.6. The 2016 energy saving regulation allows a U-value of 0.28. The building will be heated with an air-to-water heat pump plus a fireplace, and possibly decentralized ventilation with heat recovery.

What do you think? I couldn’t find anything online or here. :-(

May I ask how much extra the PP4 blocks cost?