ᐅ Is it worth investing in insulation beyond the standard requirements for new construction?

Concepts like these from the prefab house provider Kampa initially sound quite good, and there are many people in forums who believe that nowadays you shouldn’t build a house with a U-value above 0.15.

On the other hand, when you calculate the raw numbers, I struggle to understand how insulation beyond what is necessary can actually be cost-effective.

Let’s take a 140-150 sqm (1500-1600 sq ft) house with 1.5 stories as an example. This would have an exterior wall surface area of about 170 sqm (1830 sq ft) (excluding roof, top floor ceiling, foundation slab, and windows, with a relatively high knee wall as we plan).

The local provider, in a standard case, offers a U-value of 0.21, while Kampa advertises 0.11. According to a U-value calculator, the local provider’s wall consumes 16 kWh/m² per year, and the 0.11 U-value leads to 7 kWh/m² per year. Calculated over the surface area, that’s 2,720 kWh versus 1,190 kWh. With an air-to-water heat pump with an annual performance factor of 4.1 (yes, these are available for about 4,000 EUR – greetings to the purple forum), this equates to 663 kWh_el versus 290 kWh_el. So, you save about 373 kWh just from the exterior wall construction. Variant A: standard solid construction and Variant B: passive house wall. In strict monetary terms, that’s about 93.25 EUR per year or 7.77 EUR monthly installments.

Over 20 years, the difference adds up to 1,865 EUR. In 20 years!!!

Of course, additional savings come from insulating the foundation slab, roof, and better windows in a passive house, but those also require separate higher investments.

On the other hand, a photovoltaic self-consumption system can save a lot, especially during transitional seasons (self-generated electricity costs less than half compared to grid electricity). This is particularly true for an energy-saving standard house, which benefits significantly from PV power during these periods, unlike a KFW40-level house where heating is mostly needed only in the coldest winter months.

The question in the end is: is it even worth it, or is the current energy-saving regulation standard already so strict that the economic feasibility has long been exceeded?

There’s also a bit of a question between timber frame prefab houses versus solid construction. Only with a timber frame prefab house can you achieve a high insulation value for the exterior facade with a reasonably manageable wall thickness (in cm). In my opinion, this is the only advantage of a timber frame prefab house compared to solid construction.

We keep having these discussions. My position is that for a solid construction house, a KfW 70 standard makes sense. It is difficult to compare this with a timber frame house. Or how did you want to quantify the additional costs for the Kampa exterior wall compared to the standard solid construction wall?

You already pointed it out yourself: insulating no longer pays off financially after a relatively early point. The energy regulations are quite strict, which is why house prices have also increased significantly in recent years. Insulation is more about environmental benefits than saving money. However, this is not necessarily true if you own your own wind turbine and use it to operate an air-to-water heat pump (which is conceivable, for example, in rural areas).

Energy cost increases and resale value should perhaps be taken into consideration. In my opinion, a higher quality standard should also be reflected in a potential resale.

And even if the costs triple - you can see from Grim’s numbers that it hardly makes a difference over a year.

There’s a reason why I didn’t go along with the insulation craze to that extent.

Sure, the price increase is a relatively weak argument. However, the lifespan of the building is ideally not just 20 years, and personally, I would rather spend the money with a local tradesperson than give it to the energy supplier.

“Insulation craze” is the right term. In our lifetime, we won’t recover the additional costs of higher insulation. For the above reason, I chose to go with somewhat better insulation, which was purely an ideological decision.