Thermal insulation, Energy Saving Ordinance, KFW 70 / 55 / 40 - Your experiences

Hello everyone, as we would say around here

since I am now somewhat hooked on the forum and more and more topics interest me, the question regarding the right and "best" insulation currently arises for me (still purely out of interest, but certainly also practical at some point). I have deliberately put the word best in quotation marks, as there are always different tastes and areas of application.

I am well aware that a house built to a standard 0815 level does not require insulation below U=0.14 W/(m²K). Therefore, I tried to look up the following values regarding the Energy Saving Ordinance requirement and the KfW houses 70 / 55 / 40.

I came to the following values for the heat transfer 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 values mentioned above, it already becomes clear what needs to be done in terms of house insulation to meet certain standards. As written above, other factors also come into play like roof, upper floor and ground floor windows, possibly ceiling on upper floor, exterior wall including roller shutter box, exterior door, exterior wall and floor slab. But somehow one has to start

As a layman, I would now be interested in the comparison from KfW 70 standard to KfW 55 with regard to the exterior wall. Since this point is, for me at these values, the only difference regarding the points above. But feel free to also share your info and experience concerning, for example, windows.

To achieve a value of the exterior wall of U 0.18 W/(m²K), there seem to be different possibilities, as I have also read in other threads:

[*]monolithic wall construction
[*]functional exterior wall
[*]double-shelled exterior wall

For me personally, only the monolithic wall construction comes into consideration. Of course, one must keep in mind that ultimately for certain values, e.g. a 40 cm thick wall is required.

Windows are often spoken of as loopholes in the sense that there is probably so much material around them. How have you decided, or how would you possibly evaluate this from your experience?

Which stones have you possibly had good or also bad experiences with?
For example:

[*]Lightweight concrete plan block NeoStone U-value of 0.17 W/(m²K)
[*]Lightweight concrete plan block “SK08” U-value up to 0.18 W/(m²K)
[*]ThermoPlan MZ8 (mineral wool) – 42.5 cm 0.18 W/(m²K)
[*]Poroton T9 – 36.5 cm 0.23 W/(m²K) – Therefore only suitable for KFW 70
[*]Poroton T8 – 42.5 cm 0.18 W/(m²K)
[*]Poroton T8 – 49 cm 0.15 W/(m²K)
[*]Poroton T7 – 42.5 cm 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 0.18 W/(m²K)
[*]Ytong aerated concrete 0.08 – 42.5 cm 0.18 W/(m²K)
[*]Ytong aerated concrete 0.09 – 48 cm 0.18 W/(m²K)

So, start typing

You are going about it the wrong way - the wall structure is only ONE factor in the calculation - even the choice of heating type gives you points for KFW calculations.

Why only monolithic?

In any case, this approach gets you nowhere, you have to look at the overall package... and that is what a planner does.

You are approaching the matter incorrectly – the wall construction is only ONE factor in the calculation – even the choice of heating system earns you points for KFW calculations.

Why only monolithic?

In any case, your approach won’t get you anywhere, you have to look at the overall package... and that’s what a planner does then .

Good morning Lexmaul79,

Yes, I understand that ultimately the overall concept has to be right or fit and that, as mentioned above, there are many influencing factors. As you already say, heating, windows, etc. also play a role. Nevertheless, I think the facade or exterior wall (the wall construction) and insulation are still a major part, aren’t they? My primary concern here is whether one of the bricks for the monolithic construction should be preferred or whether there are bricks filled with, for example, perlite that one should rather avoid and instead go for variants with mineral wool.

The reason I ultimately decided on monolithic construction is primarily that I do not want external insulation. Possibly this is a personal preference so far, but maybe also a cost issue. I attended a lecture last week about energy-efficient building. They also introduced “prefabricated walls,” i.e., ready-made elements made of wood and other materials. They explained the advantage that the basic framework of the house can stand within 3-4 days and that the wall thickness is about half that of the brick-on-brick construction with the same U-value. Nevertheless, I still tend to favor monolithic construction.

There are different manufacturers, bricks, and above all variants. I would be very interested in your experiences, if any. Also regarding the topic of thick walls and the possibly loophole-like appearance.

On the topic of loophole optics, I would like to add my two cents. We have a wall thickness of 43.5 cm on the ground floor (plus interior plaster, brick facade) and 35.5 cm on the upper floor (plus interior plaster, ETICS). In both floors, the feeling at the window openings is the same; loopholes are not visible from outside or inside. I think this "problem" can only occur with very small windows, e.g. with small strips of light - but I have no experience with that. However, we have never dealt so intensively with the building materials. The wish was brick at the bottom, plaster above ==> Auftrag an den Planer, ein mind. KfW 70 Haus mit diesen Vorgaben zu entwerfen, wie ist egal, da alles eine Glaubensfrage ist

Hello,

For me, it is primarily about whether one of the stones should be preferred for the monolithic construction, or if there are stones, for example filled with perlite, that one should rather avoid and opt for the variants with mineral wool

There is no single "one and only" wall construction; there are so many different preferences of individuals, all of which can be accommodated

What you - despite all your need for information - forget: for example, if your property is located in an earthquake zone, it can very well happen that you have to say goodbye to your "desired" stone. It may also be that you decide on a building partner whose preferred material is clinker brick, but beforehand you had fixed on aerated concrete. And then?

Also on the topic of thick walls and the possibly loophole-like appearance.

You find "loopholes" in true passive houses and only then if the money for windows suitable for passive houses is lacking (usually twice as expensive as "normal" windows)

Regards from the Rhineland

On the topic of loophole optics, I would like to add my two cents. We have a wall thickness of 43.5 cm on the ground floor (plus interior plaster, brick facade) and 35.5 cm on the upper floor (plus interior plaster, ETICS). In both floors, the feeling at the window openings is identical; loopholes can neither be seen from outside nor inside. I think this "problem" can only occur with very small windows, e.g., small bands of light – however, I have no experience with that. We have never really dealt intensively with the building materials, though. The wish was brickwork at the bottom, plaster on top ==> order to the planner to design at least a KfW 70 house with these specifications, how is irrelevant, as everything is a matter of belief

Thanks already for your feedback regarding the loopholes. Is there a particular reason why you chose a brick facade with wide stones at the bottom and a smaller one including ETICS at the top? So two different variants? Of course, probably ultimately to achieve the U-value for KfW 70, but why different?