How thick should exterior walls be?

Hello, we have just received quotes from house construction companies. The exterior walls are specified as 17.5 cm there. That seems a bit thin to me? Who can help me with their knowledge or experience? We are building a bungalow style with a heat pump (if that is relevant...).

For an energy-saving construction method, a U-value of the exterior wall and roof covering below 0.17 W/m²K for the entire component (...not just over the insulation area...) should be aimed for.

In a bungalow construction method, the AV-ratio (ratio of the exterior surface area to the volume of the building) is rather less optimal, so a low U-value of the building envelope should be targeted for energy-efficient construction.

Heat pump! - With a well-insulated building envelope, the heating load decreases, these are optimal conditions (low temperature difference) for particularly energy-saving operation and better annual performance factors of a heat pump. If the building is less well insulated and the heat pump used is an investment-friendly compromise (e.g., an air/water heat pump), frequent use of the electric heating element may occur and the consumption can be higher than that of a condensing gas boiler.

Regards T.H.

....If the building is less well insulated and the heat pump used is a cost-effective compromise (e.g., an air/water heat pump), then the frequent use of the electric heating element may occur and consumption can even be higher than that of a condensing gas boiler.

This is not correct! The energy consumption with a heat pump, regardless of the type, is always lower compared to a heat generator based on the combustion principle, e.g., condensing gas boiler, provided that environmental energy components have been utilized! However, consumption costs can be higher with insufficiently or poorly planned systems. Energy is measured in kWh, not €! Furthermore, air heat pumps are generally not a compromise, because the somewhat lower annual performance factor compared to, for example, brine systems, often does not justify the additional costs for the source development. However, air heat pumps only make sense if all boundary and framework parameters are suitable and an exact dimensioning and design of the entire system has taken place. Unfortunately, one repeatedly finds general contractors/builders on construction projects where air heat pump combination units have been installed quasi ad libitum without sufficient dimensioning. In such cases, consumption costs can become unpleasantly high due to the resulting low annual performance factor.

Hi,

I think the question about the right wall thickness has already been discussed 936 times here. And somehow, you always come to the conclusion that this question cannot be answered generally. It depends on your requirements.
The material plays a big role --> [Kalksandstein], [Porenbeton], [Poroton], wood. All these materials meet different requirements in various ways. Keyword sound insulation, thermal insulation, statics.

Then your building must be considered as a whole. The interaction between the building construction and the plant engineering must fit perfectly together.

As a general rule, one can only say that it makes sense to design the building envelope so that not much energy needs to be generated to keep your place warm.

Cheers