Many clients called me explaining that they have hired a contractor to soundproof their bedroom or basement apartment. The contractor added insulation. However, the result of the renovation was not satisfactory. The noise was almost as bad as before the renovation.
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Unfortunately, many contractors consider adding insulation (either bats or blown-in) into walls and ceilings as soundproofing. The origin of this misconception is probably the promotion of insulation as a soundproofing product.
How much soundproofing do homeowners need?
This question is answered in my other blog article.
Wood-frame wall without insulation has noise resistance of STC 32 [reference 1]. And, if insulation is added by bats or blowing it in, the STC value is unchanged, STC 32 [2].
A typical hollow floor/ceiling assembly without insulation between joists has STC 26 [3]. If insulation is added by bats or blowing it in, the STC value is increased to STC 29 [4]. A slight, hardly noticeable improvement.
In other words, adding insulation to an existing wall or floor/ceiling assembly is not a good use of effort and money. It does not noticeably improve the soundproofing of the assembly.
How to recognize a bad soundproofing contractor.
The first telltale sign is when a contractor gives you a wide range of STC values. Here is an example taken verbatim from a Toronto contractor quote to an unsuspecting client:
"The STC varies from 30 to 75 based on the thickness and the other material that are existing or will be installed"
Based on the above statement, you can expect (but not guaranteed) the low end of the range.
The second telltale sign is promising an unreasonably high STC value. Here is an example taken verbatim from the same Toronto contractor:
"It called decoupling and we layer multiple type of soundproofing material for an STC of 100 starting at 13$ per sqft."
STC 100 is impossible in any standard residential construction. A concrete wall 64 inches thick provides only STC 88.
How to soundproof properly with insulation?
The soundproofing needs to be improved by at least STC 10 and possibly more to make a noticeable difference. An improvement of 10 reduces the noise transmitted through the partition by 50%.
Therefore, the only way of obtaining this improvement is to rebuild the partition with a proper soundproofing assembly that includes insulation. Adding insulation alone will not improve soundproofing.
Please let us know about your unsuccessful soundproofing job. Use the form below.
If you would like to request a visit from a soundproofing consultant to advice on your soundproofing situation, click below.
References:
[1] Ontario Building Code 2012; MMAH Supplementary Standard SB-3, Wall No. W1e
[2] Ontario Building Code 2012; MMAH Supplementary Standard SB-3, Wall No. W1c
[3] Ontario Building Code 2012; MMAH Supplementary Standard SB-3, Wall No. F3c
[4] Ontario Building Code 2012; MMAH Supplementary Standard SB-3, Wall No. F3d
