ᐅ Thermal Insulation, Energy Saving Regulations, KFW 70 / 55 / 40 – Your Experiences

Hello everyone, as we would say here,

since I have now become quite engaged with this forum and am interested in more and more topics, the question of the right and “best” insulation has come up for me recently (still purely out of interest for now, but surely also practical at some point). I deliberately put the word best in quotation marks because there will always be different preferences and use cases.

I am fully aware that a standard house usually does not require insulation below U=0.14 W/(m²K). Therefore, I tried to look up the following values regarding the energy-saving regulations and the KfW houses 70 / 55 / 40.

I came up with the following values for the thermal transmittance coefficient:

Reference building according to Energy Saving Ordinance 2014
U-value | Roof 0.20 W/(m²K), Windows 1.30 W/(m²K), Exterior wall 0.28 W/(m²K), Basement wall 0.35 W/(m²K), Floor slab 0.35 W/(m²K)

KfW Efficiency House 70
U-value | Roof 0.17 W/(m²K), Windows 0.90 W/(m²K), Exterior wall 0.23 W/(m²K), Basement wall 0.25 W/(m²K), Floor slab 0.25 W/(m²K)

KfW Efficiency House 55
U-value | Roof 0.17 W/(m²K), Windows 0.90 W/(m²K), Exterior wall 0.18 W/(m²K), Basement wall 0.25 W/(m²K), Floor slab 0.25 W/(m²K)

KfW Efficiency House 40
U-value | Roof 0.15 W/(m²K), Windows 0.80 W/(m²K), Exterior wall 0.14 W/(m²K), Basement wall 0.20 W/(m²K), Floor slab 0.20 W/(m²K)

With the above values, it becomes clear what needs to be done regarding home insulation to meet certain standards. As mentioned above, other factors also play a role, such as roof, upper and ground floor windows, possibly the ceiling in the upper floor, exterior wall including roller shutter box, exterior door, exterior wall, and floor slab. But you have to start somewhere.

What I am curious about as a layperson is the comparison between the KfW 70 standard and the KfW 55 regarding the exterior wall. For me, this point represents basically the only difference related to the values mentioned above. Of course, you are also welcome to share your information and experience regarding windows, for example.

To achieve an exterior wall U-value of about 0.18 W/(m²K), there seem to be different options, as I have read in other threads, such as:

• Monolithic wall construction
• Functional exterior wall
• Double-shell exterior wall

For me personally, only the monolithic wall construction is really an option. Of course, you have to consider that you end up with, for example, a 40cm (16 inches) thick wall to achieve certain values. Often, the windows are then described as “loophole-like” because there is so much material around them. How did you decide, or how would you evaluate this from your experience?

What types of blocks or bricks have you had good or bad experiences with? For example,

• Aerated concrete plan block NeoStone U-value 0.17 W/(m²K)
• Aerated concrete plan block “SK08” U-value up to 0.18 W/(m²K)
• ThermoPlan MZ8 (mineral wool) – 42.5 cm (17 inches) 0.18 W/(m²K)
• Poroton T9 – 36.5 cm (14 inches) 0.23 W/(m²K) – therefore only suitable for KfW 70
• Poroton T8 – 42.5 cm (17 inches) 0.18 W/(m²K)
• Poroton T8 – 49 cm (19 inches) 0.15 W/(m²K)
• Poroton T7 – 42.5 cm (17 inches) 0.15 W/(m²K)
• UNIPOR W09 - Approval Z-17.1.-1042 | 0.20 W/(m²K) – therefore only suitable for KfW 70
• UNIPOR WS07 CORISO | Approval Z-17.1.-1074 0.18 W/(m²K)
• Ytong aerated concrete 0.07 – 36.5 cm (14 inches) 0.18 W/(m²K)
• Ytong aerated concrete 0.08 – 42.5 cm (17 inches) 0.18 W/(m²K)
• Ytong aerated concrete 0.09 – 48 cm (19 inches) 0.18 W/(m²K)

Now, go ahead and type away!