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

Created on: 17 Feb 2015 17:09

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!

Sebastian7918 Feb 2015 12:57

Brick increases the wall thickness – > ventilated cavity plus the brick itself

Häuslebau3r18 Feb 2015 13:01

Bauexperte schrieb:
Hello,

There is no single “best” wall construction method; different people have different preferences, and all can be accommodated.

What you forget – despite all your need for information – is this: if your plot, for example, is located in an earthquake zone, you might have to give up your “preferred” type of brick. It’s also possible that you choose a building partner whose favored material is hollow bricks, but you were previously fixed on aerated concrete. Then what?

“Loopholes” appear in true passive houses, and also only when the budget doesn’t allow for windows suitable for passive houses (which usually cost twice as much as “normal” windows).

Regards, Bauexperte

Hello @Bauexperte, regarding the plot, there are definitely no issues related to earthquake zones; I know that for sure. As for the building partner, I have to admit that I hadn’t considered that before. But in other cases, one usually contacts various building partners and requests quotes with the idea of using a certain type of brick, which the builder might also recommend.

About the loopholes, I was only told about that so far; I wasn’t aware of it personally and therefore didn’t consider it. But, for example, with Ytong, there are different bricks with varying thicknesses and values, yet they have the same U-value.

Sorry, I didn’t mean for this to turn into a debate.

Häuslebau3r18 Feb 2015 13:14