The effort to meet new carbon emission goals includes reducing thermal losses from buildings. Retrofit effort to improve thermal insulation is a perfect opportunity, with the help of an acoustical engineer, to also improve soundproofing for acoustically sensitive spaces, with very little additional cost.
UN climate change Summit (COP 21) in Paris was completed on 7-8 December 2015. 196 countries had gathered to decide whether or not to commit to a low carbon future in a legally binding way.
Thermal insulation materials, when applied properly in a wall assembly designed to reduce thermal loss, can also provide increased sound transmission loss through the wall assembly.
Types of thermal insulation improvements
Heat loss of a building is reduced by improving thermal insulation of the building envelope, including exterior walls, windows doors and roof. Read below how these thermal improvements can also improve soundproofing of the building against exterior sounds (traffic noise, noise from night clubs, aircraft overflights, etc.).
Windows and doors
Windows and doors are typically the weakest point of soundproofing. Even if windows and doors are not being replaced, improvements for both thermal loss and noise penetration can be achieved simply by caulking any gaps and replacing worn out weather seals.
If windows and doors are being replaced, attention should be paid not only to thermal specifications, but also to acoustical specifications of the new windows and doors. Many reputable manufacturers provide information about STC value for their products.
Generally, contrary to insulation manufactures claims, there is little difference among fiberglass and rock wool insulation products with respect to their sound attenuation capabilities. When exterior walls are being upgraded to improve thermal insulation, attention should be paid to any cavities and voids in the walls. All voids should be filled with insulation; this will improve sound transmission loss of the walls.
If the energy loss retrofit plan calls for removal and replacement of interior skin of the exeterior walls, the skin should be replaced with products and assemblies that reduce sound transmission.
Simply adding a layer of suitable thermal insulation in the attic will also improve sound transmission loss of the ceiling. Fiberglass bats add about 2 dB sound transmission loss per inch of the bat thickness [Ref. 1]. For example, if thermal insulation in the attic is increased from R-20 (6.5 inches of insulation) to R-50 by adding 9.5” of fiberglass insulation, the sound transmission loss of the ceiling assembly will be increased from about 13 dB to 32 dB.
Soundproofing as part of thermal insulation improvement
Any owner who is doing building improvements to reduce heat losses, perhaps taking advantage of available government subsidies, should consider soundproofing improvements as added benefit of the project. Engaging the help of a soundproofing consultant or and acoustical engineer at the planning stages of the project will ensure that maximum soundproofing benefit is achieved at the lowest possible cost.
[Reference 1:: Master Handbook of Acoustics, Sixth Edition (2015) by Everest & Pohlmann (McGraw Hill Education), page 303.
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