ᐅ Sound Insulation: What Thickness for Cavity Wall Insulation on Interior Walls?
Created on: 9 Jul 2018 16:26
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Don_Mikele87D
Don_Mikele879 Jul 2018 16:26Hello everyone,
Today, I want to discuss sound insulation. We are currently building the walls for our single-family house in cooperation with a local carpenter. There are some differences of opinion between our architect and the craftsman regarding the insulation of the interior walls:
The wall structure is as follows (from left to right):
12.5 mm (0.5 inch) gypsum board
15 mm (0.6 inch) OSB
120 mm (4.7 inches) wooden studs including cavity insulation
15 mm (0.6 inch) OSB
12.5 mm (0.5 inch) gypsum board
Mineral wool is being used as insulation.
The issue:
The carpenter wants to fill the cavity completely with 120 mm (4.7 inches) thick insulation, meaning the full depth of the stud. According to the architect, however, for better soundproofing, it’s preferable to fill the cavity only partially, with 40-60 mm (1.6-2.4 inches) max.
As a layperson, I’m caught in the middle and trying to understand the situation. Searching online yields varying arguments:
1. In favor of 40-60 mm: insulation that doesn’t fully connect both walls, leaving an air gap, absorbs sound better from an acoustic standpoint.
2. In favor of 120 mm: more insulation means more mass; more mass absorbs sound better.
Are there any experts who can confirm or refute either position? Any personal experiences? This question is solely about the thickness of the cavity insulation, not about other soundproofing measures such as vibration-free suspensions, etc.
Thank you in advance!
Today, I want to discuss sound insulation. We are currently building the walls for our single-family house in cooperation with a local carpenter. There are some differences of opinion between our architect and the craftsman regarding the insulation of the interior walls:
The wall structure is as follows (from left to right):
12.5 mm (0.5 inch) gypsum board
15 mm (0.6 inch) OSB
120 mm (4.7 inches) wooden studs including cavity insulation
15 mm (0.6 inch) OSB
12.5 mm (0.5 inch) gypsum board
Mineral wool is being used as insulation.
The issue:
The carpenter wants to fill the cavity completely with 120 mm (4.7 inches) thick insulation, meaning the full depth of the stud. According to the architect, however, for better soundproofing, it’s preferable to fill the cavity only partially, with 40-60 mm (1.6-2.4 inches) max.
As a layperson, I’m caught in the middle and trying to understand the situation. Searching online yields varying arguments:
1. In favor of 40-60 mm: insulation that doesn’t fully connect both walls, leaving an air gap, absorbs sound better from an acoustic standpoint.
2. In favor of 120 mm: more insulation means more mass; more mass absorbs sound better.
Are there any experts who can confirm or refute either position? Any personal experiences? This question is solely about the thickness of the cavity insulation, not about other soundproofing measures such as vibration-free suspensions, etc.
Thank you in advance!
A carpenter installing mineral wool in walls? Our carpenter would never do that and would only install wood fiber insulation. The "STEICO Construction Manual Interior Wall" states that an 80% fill is recommended for soundproofing. However, I’m not sure if this also applies to mineral wool.
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Don_Mikele8710 Jul 2018 11:21Great, thanks for the feedback. Then I have another research lead 🙂
In the end, he installs whatever the client orders. And that, in turn, depends on the budget ;-) He probably would have preferred blown-in insulation as well...
world-e schrieb:
A carpenter installing mineral wool in walls? Our carpenter would never do that, only install wood fiber insulation.
In the end, he installs whatever the client orders. And that, in turn, depends on the budget ;-) He probably would have preferred blown-in insulation as well...
K
Knallkörper10 Jul 2018 11:56Don_Mikele87 schrieb:
1. For 40-60 mm (1.6-2.4 inches): Insulation does not connect both walls, air gap absorbs sound, etc. -> acoustically better
2. For 120 mm (4.7 inches): More insulation = more mass; -> More mass absorbs sound better.In my opinion, both statements are misleading.
1. The connection of the walls through the insulation is not relevant for sound transmission because the insulation is not rigid enough. If anything, the fact that the insulation is in contact might have a positive effect: then both wall layers are slightly damped, meaning they cannot vibrate freely. However, sound transmission from one wall to the other is mainly carried by the wooden structure.
2. More mass is a weak argument; it probably does not add more than 5 kilograms per square meter (1 pound per square foot).
Much more important is to ensure that the flanking elements are well decoupled, such as the screed (concrete floor layer), and that no sound bridges are introduced.
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Don_Mikele8710 Jul 2018 16:38Thank you very much, that already provides some reassurance.
Regarding sound bridges: Of course, the screed will be decoupled using joint tape. Additionally, we are constructing the interior walls with timber stud framing, with the ceiling joists resting on top. The cavities will also be appropriately insulated here, and the drywall sheathing on the wall will continue up to the top edge of the ceiling joists – essentially like a kind of barrier wall. Only then will the ceiling sheathing be installed and joined to the wall. I hope it’s clear what I’m trying to explain here in layman’s terms ^^
Is it necessary for the ceiling joists to rest on some kind of sealing tape to decouple them? How is this handled with the final ceiling sheathing, specifically at the points where the ceiling sheathing meets the wall as described above? Are there any major points I might have overlooked? (Possibly the use of sound-absorbing specialist boards, at least for the bedrooms and the utility room).
Regarding sound bridges: Of course, the screed will be decoupled using joint tape. Additionally, we are constructing the interior walls with timber stud framing, with the ceiling joists resting on top. The cavities will also be appropriately insulated here, and the drywall sheathing on the wall will continue up to the top edge of the ceiling joists – essentially like a kind of barrier wall. Only then will the ceiling sheathing be installed and joined to the wall. I hope it’s clear what I’m trying to explain here in layman’s terms ^^
Is it necessary for the ceiling joists to rest on some kind of sealing tape to decouple them? How is this handled with the final ceiling sheathing, specifically at the points where the ceiling sheathing meets the wall as described above? Are there any major points I might have overlooked? (Possibly the use of sound-absorbing specialist boards, at least for the bedrooms and the utility room).
What does the ceiling construction look like? There should definitely be decoupling between the wall and the ceiling. Partial insulation of the walls is more practical than full insulation. To improve soundproofing between two rooms, doubling the drywall can already help by increasing the mass. (And, for example, using gypsum fiberboards instead of gypsum plasterboards.)
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