What is Spray Foam Insulation?

As many of us know, insulation provides a huge opportunity for energy savings in your home. The Department of Energy suggests that the best way to cost-effectively make your home more comfortable year-round is to add insulation to your attic (including the trap or access door)1. What some of you may not know is that spray foam insulation can offer a significant sound barrier. To test this theory, ARiES Solar completed a sound test at The Oliver Hotel in downtown Knoxville.

Spray foam insulation is insulation with expanding properties that fill gaps that traditional fiberglass insulation often fails to fill. There are two types of spray foam insulation: open and closed cell structured insulation. Both create air barriers as well as sound barriers. Closed cell spray foam is generally used on exterior walls and attic spaces because the compact cell structure creates a great moisture barrier and higher R-value. Open cell is generally used on interior walls because a less compact cell structure does not create a good moisture barrier and has a lower R-value. Traditional insulation products can sag and settle, resulting in a reduction in thermal efficiency. Due to the expansive properties of spray foam, the spray foam does not sag or lose its thermal efficiency and adds to the structural integrity of the structure where it is located such as the wall or roof.

Working with David Ball, President of Emps, Inc., we conducted a sound test to the ASTM E336-11 Standards that contained a pink noise that tests a full range of frequencies and decibels (dB). The results of our sound test (shown below) proved that all frequency and noise had been reduced by 10 dB, resulting in the sound intensity of the insulated walls compared to the uninsulated walls being cut in half. All sensitive noises within the voice and telephone range (300 to 3000 Hz) had been reduced by 20 dB, meaning the sound intensity of the insulated walls had been cut to a quarter of the sound intensity of the uninsulated walls.

We have provided a few of our test results of the spray foam insulation below.  To put into perspective where common sounds fall on this graph, Household telephone falls within 2000 to 3000 Hz and Voices fall within 300 to 3000 Hz. Sound test results:



All Sounds Graph

During the sound test, we also tested a brick wall to measure its noise barrier characteristics. Our results found that the decibel vs. frequency graphs for an insulated wall and brick wall followed a similar line (shown below).

Brick Wall Graph

Insulated Graph

While conducting the sound study to determine the effectiveness of the spray foam insulation on noise reduction, we had the opportunity to see where else sound was permeating from room to room. Although there was some leakage of sound over the walls, the doors were found to have the largest noise leak. If you add up the air gap around the edge of a door, the total opening can add up to a “2×5-size (“mail slot-size”) opening for sound to pass through. As we observed, David Ball emphasizes that sealing around doors is just as important as adding spray foam.


Calculating the payback of additional insulation – DOE – http://energy.gov/energysaver/articles/estimating-payback-period-additional-insulation


Human Ear – Hearing Range