ᐅ Insulating a New Build with 36.5 cm Aerated Concrete Blocks?

bygoran schrieb:
We are building without KfW funding but want to insulate as well as possible.

According to the U-value calculator, I need to use 200mm insulation.

Good grief, be glad you didn’t agree to the deal of “sticking hazardous materials on your exterior wall in exchange for subsidies.” You can also glue half a meter of foam boards onto the wall – structurally it’s possible since that stuff doesn’t weigh much. In my opinion, that’s foolish thinking, believing that heat can just be trapped like that. The theoretical calculations work perfectly well – but those theories also ignore the fact that normal outdoor air always contains some moisture. If you ask me, that’s government-subsidized mold growth. In ten years, houses like that won’t get fire insurance anymore, and by then, enough of them will have burned down.

Nordlys schrieb:
But I think these things are a scam. When it’s really cold, you end up heating with electricity anyway. How eco-friendly is that?

It doesn’t have to be that way, since these overly optimistic calculations are only about “theoretical” savings anyway. Reality just gets in the way and measurements shatter illusions. It’s a scam, yes, but sometimes it’s a “political decision.”

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@Iktinos: You say I might seem simple-minded from your perspective, but so far, the pragmatic approach of "never be the first" and "keep it simple" has served me well. It’s winter now, and the electricity meter is spinning quickly in my daughter’s new build, where she bought a pump from Junkers due to the small KfW subsidy. We haven’t even had a severe winter here in the north, just a steady temperature around 0°C (32°F) since New Year’s. And the electricity keeps flowing...

Nordlys schrieb:
@Iktinos :
We are in winter, the electricity meter is running quite fast in the new build ...

Same here... Refrigerator and other appliances do require electricity after all.

Ickes schrieb:
The exterior wall is aerated concrete (AAC) block PPL 2, thickness 24cm (9.5 inches), with an external thermal insulation composite system (ETICS) of 14cm (5.5 inches). He suggested that you could save quite a bit of money while maintaining the same insulation value by using a 36.5cm (14.4 inches) thick AAC block instead of the 24cm (9.5 inches) one. The mason doesn’t earn more per hour for the extra work, and generally prefers—and is faster—installing the larger block (apparently using a crane).

Normally, standard AAC blocks are not installed using a crane, as far as I know. Only large prefabricated elements or the significantly heavier sand-lime bricks are handled that way.

The thermal insulation value (U-value) of a 24cm (9.5 inches) PPL 2 block plus 14cm (5.5 inches) ETICS is about 0.15, while a 36.5cm (14.4 inches) PPL 2 block alone is around 0.23.

In practice, however, this difference hardly makes a noticeable impact since ventilation losses and heat loss through window areas have a much greater effect.

According to common opinion, the solution without additional external insulation is significantly more cost-effective in the long term, even if heating costs are slightly higher. The maintenance and refurbishment efforts over the building’s lifetime are clearly reduced.

We will also be building monolithically.

Grym schrieb:
Regular aerated concrete blocks are usually not installed using a crane, as far as I know. Only large precast elements or the significantly heavier sand-lime bricks are handled that way.

I believe the distinction for aerated concrete lies between blocks that are 50cm (20 inches) and 62.5cm (25 inches) long, determining whether they can still be considered "two-person blocks" or if a small lifting device is used.

So this seems to be related to the human arm span, not just the absolute weight. Something that is harder to grasp feels effectively heavier.

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The heating element is, of course, not primarily designed to defrost the outdoor unit.

However, combining a heat pump with solar thermal is a rather unusual approach. Heat pumps generally don’t perform well with high hot water temperatures, so using a buffer tank is not ideal. On the other hand, solar thermal systems require a large buffer tank. This means two systems are being combined that don’t really work well together. It would be better to install photovoltaic panels on the roof and use the electricity generated for self-consumption to power the heat pump. That works well. In that case, a buffer tank is not necessary.