ᐅ Same Price: KfW 55 with Poroton solid masonry OR KfW 40 with Poroton insulated exterior wall system (ETICS)?

Hello everyone,

The recent shock with one house provider has settled, and we have started over again. We have made good progress, and one provider has now drawn our house and created several offers with different masonry options based on our request. We compared the financing and calculated it down (KfW 40 with 100,000 euros for 1.54% interest rate target).

Assumptions: The houses vary in price, but the more expensive one qualifies for KfW financing, so the costs balance out. The question now is:

Exactly the same house,

a) KfW 55 with Poroton (brick - 36.5 cm (14 inches) thickness / Thermo Plan S-8 or T-8), 36.5 cm (14 inches) monolithic construction

OR

b) KfW 40 with Poroton (brick - 24.0 cm (9.5 inches) thickness / Thermoplan T-14) plus 18 cm (7 inches) Styrodur insulation

For the KfW 40 house, the remaining debt after 10 years is 4,000 euros higher; however, assuming an annual heating cost saving of 200 euros compared to the KfW 55, this difference would be recovered within 20 years. Therefore, I would say the overall cost or remaining debt after 10 years is basically the same.

What would you choose and why? Can it be said that a KfW 40 house has a higher resale value?

Thanks and best regards!

Ari_tau schrieb:

What would you choose and why? Can it be said that a KfW 40 house has a higher resale value?

In the end, this is a matter of personal belief.

I would choose the KfW 40 house. Why? Better efficiency (at least on paper) and, in my opinion, slight advantages when reselling (I’m not someone who lives in just one property for their entire life).

However, these are completely different construction methods. You could say "KfW 40 is simply better," but you could also argue "KfW 40 with ETICS (external thermal insulation composite system) uses problematic materials and the facade gets dirty quickly." Or the sound insulation varies. There are several differences, some of which are only perceived.

Hello,
if you ask me: this is a completely wrong way to look at it. Whether the house still has 4,000 euros more outstanding debt in 10 years, or how big the heating cost difference is over 10 years, or whether a sack of rice falls in China – it’s all about equally important.

Much more important, in my opinion, is sound insulation. And with the T14’s 18 cm (7 inches) insulation, it’s already borderline. We have exactly that combination. It’s just about acceptable, but you can definitely hear the party next door through the wall.

A T8 has about the sound insulation of a tent, which for me would be a complete no-go.

Best regards,

Andreas

andimann schrieb:

In my opinion, sound insulation is much more important. With the T14 and 18 cm (7 inches) of insulation, you’re really pushing the limits. We have exactly that setup. It’s barely acceptable; you can definitely hear the party in the neighbor’s garden through the wall.

A T8 provides sound insulation more like a tent, which would be a complete no-go for me.

Good point, I was assuming similar values regarding sound insulation.

Do I understand your statement correctly that the T8 (here in monolithic construction) offers less sound insulation than the T14 with external thermal insulation composite system (ETICS)?

Hi,

Ari_tau schrieb:

Do I understand your statement correctly that the T8 (in monolithic construction here) has less sound insulation than the T14 with external thermal insulation composite system (ETICS)?

Correct. And significantly less. Unless you mean the T8 filled with mineral wool. Check the websites of the potential brick manufacturers. There you can find datasheets that also include the sound insulation values.

Best regards,

Andreas

andimann schrieb:

Hi,

Correct. And significantly so. Unless you are talking about the T8 filled with mineral wool. Check the pages of the potential brick manufacturer. There you can find datasheets that also include the sound insulation rating.

Best regards,

Andreas

Already done in the meantime 😉 I’m not sure how much of a difference 5 dB makes, but the difference is there. On the left is the T8, on the right the T14. Also noticeable from the bulk density of 0.6 and 0.7 respectively.