ᐅ Exterior Wall for KfW 40 (+) Standard: With or Without External Thermal Insulation Composite System (ETICS)?
Created on: 18 Feb 2021 11:23
F
Franke86
Hi everyone,
I need some advice. I’m currently planning my detached single-family house. The developer’s standard offering includes 24 hollow bricks plus 14 cm (5.5 inches) external wall insulation (EWI).
Since I want to build to KfW 40 (Plus) standard, they told me I would need 24 hollow bricks plus 18 cm (7 inches) EWI, which would cost an additional €1800.
What would you recommend? Is using EWI still considered "up-to-date," or is it becoming less common?
One advantage mentioned to me is that this creates a cavity wall construction, which offers better insulation and should also help prevent mold.
I also wanted to get some pricing for purely monolithic walls, and I received the following offer (standard is 24 hollow bricks + 14 cm (5.5 inches) EWI):
Which option would you choose, and are these additional costs typical or too high?
Brief details about the house: It’s a detached single-family home with a flat roof, approximately 160 sqm (1722 sq ft) living area, a ventilation system with heat recovery, and district heating for the heating.
Best regards,
Franke86
I need some advice. I’m currently planning my detached single-family house. The developer’s standard offering includes 24 hollow bricks plus 14 cm (5.5 inches) external wall insulation (EWI).
Since I want to build to KfW 40 (Plus) standard, they told me I would need 24 hollow bricks plus 18 cm (7 inches) EWI, which would cost an additional €1800.
What would you recommend? Is using EWI still considered "up-to-date," or is it becoming less common?
One advantage mentioned to me is that this creates a cavity wall construction, which offers better insulation and should also help prevent mold.
I also wanted to get some pricing for purely monolithic walls, and I received the following offer (standard is 24 hollow bricks + 14 cm (5.5 inches) EWI):
- T9 brick, thickness = 36.5 cm (14.4 inches) + €900
- 0.09 aerated concrete block, thickness = 36.5 cm (14.4 inches) + €900
- Hollow brick + 18 cm (7 inches) EWI = KfW 40+ compliant => + €1800
- T9 brick, thickness = 42.5 cm (16.7 inches) = ? KfW 40+ compliant => + €7000
- 0.09 aerated concrete block, thickness = 42.5 cm (16.7 inches) = ? KfW 40+ compliant => + €7000
Which option would you choose, and are these additional costs typical or too high?
Brief details about the house: It’s a detached single-family home with a flat roof, approximately 160 sqm (1722 sq ft) living area, a ventilation system with heat recovery, and district heating for the heating.
Best regards,
Franke86
Baranej schrieb:
The question was specifically about 24cm (9.5 inches) perforated bricks plus external thermal insulation composite system (ETICS) with 14cm (5.5 inches), and their sound insulation values, since this combination was offered by the building contractor (see first post). This was not intended as a recommendation. You’re right, I wasn’t fully aware of that.
Baranej schrieb:
Even a 17.5cm (7 inch) perforated brick has quite decent sound insulation values (~48 dB), just as a side note. Compared to what? How much is enough or too little?
Calcium silicate brick 175mm (7 inches) with a density class (RDK) of 1.8 achieves 54.2 dB, and with RDK 2.0 it reaches 55.7 dB. The additional cost is minimal.
And 55 dB versus 48 dB is definitely not "15% better," as we all know. That can make the difference between "understanding spoken words" and "hearing nothing."
In multi-family residential buildings, there are clear requirements—walls for staircases and separating walls between units need at least 53 dB. Yes, we’re not talking about a multi-family house here, but just to give a sense of what is considered "good" or "not so good." And these are minimum standards.
guckuck2 schrieb:
Did you avoid using plastic mainly INSIDE, hmm?What’s your problem? I have my opinion. You asked! And I try to avoid plastic as much as possible, yes. Seven years ago, when I built, I didn’t have the time or patience to inspect every single building component. Back then, I probably would have still used external wall insulation (ETICS). But I have lived here for 7 years, and in hindsight, I could have afforded a bit more “house” financially, so I say again: not again!
guckuck2 schrieb:
What kind of nails are you planning to use on the facade?
Nails are outdated, you use screws. There are great dowels for ETICS with plastic. At least for plastic-based ETICS, I can say they hold everything perfectly, from lamps to mailboxes. Heavy items are fixed with masonry anchors or prepared during the construction phase with a box.
I have a sunshade here that stays open up to wind force 8 and is fastened through the ETICS with two base plates and masonry anchors (thermally insulated) into the intermediate ceiling. Works well. I also think it’s great that you tell me how to attach my things to my facade. The stuff is already hanging. guckuck2 schrieb:
Don’t get me wrong, I find monolithic construction quite appealing too, I find it more appealing... my next house will be monolithic. Then I’ll also have nice thick window sills inside. That’s another disadvantage.guckuck2 schrieb:
Compared to what? How much is enough or too little?
Sand-lime brick 175mm (7 inches) with a thermal conductivity of 1.8 has a value of 54.2, and with 2.0 it is 55.7. The additional cost is insignificant. Compared to the other offers from the builder (unfilled Poroton plan brick, aerated concrete).
Sand-lime brick is naturally the frontrunner, no doubt. However, I believe it has not yet been confirmed whether this option is actually available from the builder.
Ok, let me ask differently... At the moment, this is the offer I have
Exterior wall:
Plaster 1.5 cm (0.6 inches), thermal conductivity 0.7
Hollow brick masonry thickness 24 cm (9.5 inches), thermal conductivity 0.42
External thermal insulation composite system (ETICS) thickness 18 cm (7 inches), thermal conductivity 0.035
Silicate plaster
To upgrade from the standard 14 cm (5.5 inches) ETICS to 18 cm (7 inches) ETICS, I pay an additional 1800.
Now I also have the option to go for 42.5 cm (17 inches) aerated concrete with thermal conductivity 0.09 or Poroton T9 bricks for an extra 7000 compared to the standard...
I would need to inquire about sand-lime bricks...
What would you prefer here?
Regarding the roof and sound insulation...
It is a solid flat roof that will receive additional insulation and be greened afterwards... so I think it should provide good sound insulation.
Exterior wall:
Plaster 1.5 cm (0.6 inches), thermal conductivity 0.7
Hollow brick masonry thickness 24 cm (9.5 inches), thermal conductivity 0.42
External thermal insulation composite system (ETICS) thickness 18 cm (7 inches), thermal conductivity 0.035
Silicate plaster
To upgrade from the standard 14 cm (5.5 inches) ETICS to 18 cm (7 inches) ETICS, I pay an additional 1800.
Now I also have the option to go for 42.5 cm (17 inches) aerated concrete with thermal conductivity 0.09 or Poroton T9 bricks for an extra 7000 compared to the standard...
I would need to inquire about sand-lime bricks...
What would you prefer here?
Regarding the roof and sound insulation...
It is a solid flat roof that will receive additional insulation and be greened afterwards... so I think it should provide good sound insulation.
Regarding stone replacement, I already mentioned: only if the installer has equivalent experience. What exactly is your main concern: "efficiency" in Kelvin or decibels per thousand extra cost?
Furthermore, I advise: don’t forget Pareto!
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
Furthermore, I advise: don’t forget Pareto!
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
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