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
@[B]Bookstar
Impact sound is also transmitted through a hard roofing layer.
Insulation between rafters only provides effective soundproofing up to 100mm (4 inches).
The critical factor here is the flexible, bending shells.
A roof frame is generally not decoupled.
An exposed roof structure excludes soundproofing in the rafter area.
In any case, airborne sound is less relevant here—unless you live near an airport—while impact sound is the main concern.
Impact sound is also transmitted through a hard roofing layer.
Insulation between rafters only provides effective soundproofing up to 100mm (4 inches).
The critical factor here is the flexible, bending shells.
A roof frame is generally not decoupled.
An exposed roof structure excludes soundproofing in the rafter area.
In any case, airborne sound is less relevant here—unless you live near an airport—while impact sound is the main concern.
parcus schrieb:
@Bookstar
Impact sound is also transmitted through a hard roof covering.
The insulation between rafters only provides effective soundproofing up to 100mm (4 inches).
The key factors here are the flexible shell structures.
A roof frame is not decoupled.
An exposed roof frame excludes soundproofing in the rafter area.
In any case, airborne noise is not the main issue here, unless you live near an airport; instead, impact sound is the relevant factor. This is incorrect. Airborne noise is the bigger problem, even without an airport nearby. You will hear every aircraft flying at 10km (6.2 miles) altitude, as well as every bird, rain, and wind noise.
Just look it up. The construction lacks both mass and resilience.
parcus schrieb:
@Bookstar
Both can only be on the rafter roof 🙂
Massive construction is just one building method, which is not relevant here anyway, since this is not a solid roof.I don’t understand that. Even a non-solid roof should have mass. And of course, the insulation is installed on the visible sheathing/rafters, where else?The first result when searching for visible roof truss and PUR is: “1989 Polystyrene insulation boards were gradually replaced by polyurethane roof insulation systems from x, y, t, etc. The advantage of PUR or PIR insulation panels is better thermal insulation at the same thickness. The weak points in sound insulation and wind tightness, however, remained.”
You should be able to Google that (-;
You should be able to Google that (-;
@Bookstar
Insulation beneath a hard surface like roof tiles primarily serves to reduce structure-borne noise. Alternatively, only the base battens can be insulated with rigid insulation boards on the rafters. This would act as decoupling. However, even this is usually not a requirement in a sound insulation certificate, since the attic is often the top living unit.
If someone wants to improve this themselves, they can apply concrete wood fiber boards on visible rafters or install concrete panels between the rafters. However, this still does not provide a mass of 1400 kg/m³ (87.3 lb/ft³). In principle, I would not consider airborne sound insulation a main goal in private residential construction, but rather heat protection, unless there are specific airborne noise emissions, such as near airports.
In practice (Rhine-Main Airport), I do not see the roof as the main issue, but rather the windows and other openings. The biggest problem is open windows for ventilation in summer when no mechanical ventilation system is installed.
@Snowy36
No standard insulation alone will effectively reduce low-frequency noise, even if thermal insulation is often combined with a sound insulation certificate. Different materials in the assembly usually address different frequency ranges. Whether applied on the rafters or between them is unlikely to make a significant difference. Without knowing the exact technical assessment.
Insulation beneath a hard surface like roof tiles primarily serves to reduce structure-borne noise. Alternatively, only the base battens can be insulated with rigid insulation boards on the rafters. This would act as decoupling. However, even this is usually not a requirement in a sound insulation certificate, since the attic is often the top living unit.
If someone wants to improve this themselves, they can apply concrete wood fiber boards on visible rafters or install concrete panels between the rafters. However, this still does not provide a mass of 1400 kg/m³ (87.3 lb/ft³). In principle, I would not consider airborne sound insulation a main goal in private residential construction, but rather heat protection, unless there are specific airborne noise emissions, such as near airports.
In practice (Rhine-Main Airport), I do not see the roof as the main issue, but rather the windows and other openings. The biggest problem is open windows for ventilation in summer when no mechanical ventilation system is installed.
@Snowy36
No standard insulation alone will effectively reduce low-frequency noise, even if thermal insulation is often combined with a sound insulation certificate. Different materials in the assembly usually address different frequency ranges. Whether applied on the rafters or between them is unlikely to make a significant difference. Without knowing the exact technical assessment.
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