Written by: Joe Pasma, PE, Premier SIPS Technical Manager
Other than the fact that I’m getting older and my hearing isn’t what it once was, our SIP house is very quiet. Noise from the neighborhood, wind, car traffic and kids playing outside are very hard to hear from inside our SIP house. With this being the case shouldn’t we be using SIPs in all cases where acoustical concerns are an issue? Well, not really.
My last couple of blog postings talked about how tight the building is when SIPs are used as the exterior envelope. This tight envelope also plays an important role in how quiet the building is. Without getting really technical, sound can be transmitted in two ways. These two ways are through the air, airborne, and impact, like the pounding of a drum or rain on a roof.
SIPs, because of the tightness of the building envelope, do a good job of reducing the airborne sounds. Less air leakage in the building envelope leads to a quieter building inside. The challenge with SIPs is that the materials that make them up are relatively light weight and these light materials don’t do well to stop the impact sounds or lower frequency vibrations like the kids bass on the passing car stereo.
To reduce these low frequency vibrations, heavy materials need to be used, like concrete, masonry or multiple layers of gypsum drywall. Heavier materials are sound absorbing. A measure of an assembly’s ability to “be quiet” is the STC rating. STC stands for Sound Transmission Class. Typically, STC ratings of near 50 are considered more sound proof or better able to reduce sound transmissions. Premier SIPs Technical Bulletin #25 gives STC ratings for various Premier SIP assemblies.
The takeaway from Technical Bulletin #25 is that SIPs themselves, don’t have a real high STC rating and the effort, i.e. expense, involved in creating an assembly that is sound proof, has an STC near 50, is relatively high. So, SIP buildings do a good job of reducing ambient noise but don’t do so well with the low frequency sounds. Designers should keep this in mind when acoustical performance is a big design consideration.
Remember though, if you are ever in our yard yelling for me, be sure to speak up because I won’t be able to hear you to well and it’s not really my hearing that is at fault. We just have a tight SIP house.