This article was originally published in the July/August 1998 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.


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Home Energy Magazine Online July/August 1998


Loud Planes Put Insulators to Work

Noiseproofing can cut noise levels in half and eliminate comfort problems. It's also an opportunity to find and cure indoor air quality problems.
As part of a $25 million per year federally and locally funded program, approximately 9,000 homes in the immediate area of the Minneapolis-St. Paul Airport, are being fitted with soundproofing measures. These include insulation, air sealing, and window replacements. At the same time, indoor air quality (IAQ) tests done prior to and after soundproofing (and subsequent homeowner-financed repair of the problems found) have had the effect of improving the air quality in the project homes. The data collected will be useful nationwide.

The Federal Aviation Administration Regulation Part 150 Airport Noise and Land Use Compatibility Planning program was formulated in the early 1980s to reduce noise--and thereby better the quality of life--in homes near airports. The Minneapolis-St. Paul portion of the project began in 1992. Today, the program soundproofs about 80 homes per month. Thus far, 3,600 homes have been soundproofed, and another 5,400 remain to be done.

Familiar Techniques The techniques and materials used to soundproof a house are quite similar--in some cases identical--to those used to make it more energy-efficient. Jim Fitzgerald, senior building analyst at Minneapolis' Center for Energy and Environment (CEE), says, Sound travels through air, and anywhere air can get into a house, noise can also. So air sealing is a big part of the soundproofing package, primarily through the use of caulks and sealants in the attics of the homes. Adding sound-dampening materials and mass to the homes also helps to lower the levels of noise infiltrating the inner living space.

To add mass and sound absorption, contractors in the program add heavy, well sealed storm windows and install heavy storm doors on exterior doors. In addition, contractors add air conditioning in homes that do not already have cooling, so owners can keep their windows closed during the summer. If needed, they also dense-pack the sidewalls and add as much as 14 inches of insulation to attics. Sound-deflecting dampers are also added to attic vents and chimney caps to help stop noise from traveling into the house from those holes in the building envelope.

Fitzgerald says, Most homes in Minnesota are well insulated to begin with. Still, Dave Bohac of CEE says reductions in the air infiltration rate could increase energy efficiency. According to our test results, at first we were seeing air leakage rates reduced by about 15% as a result of all the air sealing and insulation we added to the homes. As we got further along--as the contractors became more knowledgeable and improved the quality of the work--we began seeing air leakage reduced by 25%.

Mary Raasch, manager of Homeowner and Community Affairs at CEE, says the soundproofing measures have been very effective. Average noise readings have fallen by 5 to 7 decibels, and in a survey of homeowners who have had the noise reduction features in their homes completed, 93% said the modifications were effective in reducing aircraft noise levels in their homes. Ninety-one percent also said it is much easier to engage in such normal indoor activities as talking on the phone, conversing, and watching TV.

IAQ Concerns The 40- to 50-year-old ranch, Cape Cod, and one-and-a-half story homes in the neighborhoods around the airport are generally about 1,300 ft2 in size. Most use natural gas for space heating and domestic hot water. Bathroom vent fans are present in 25% of the homes; between 10% and 20% have kitchen vent fans; and almost all have a clothes dryer that vents to the outside. Program administrators were concerned that soundproofing houses like these could cause indoor air quality problems ranging from indoor moisture accumulation to backdrafting.

Before soundproofing, the Minneapolis-St. Paul Metropolitan Airports Commission and CEE check for backdrafting conditions by using blower doors to simulate worst-case depressurization scenarios. They also monitor combustion gas spillage at atmospheric vent hoods on combustion appliances and test for carbon monoxide (CO) production by gas kitchen ranges.

The owners of homes that fail IAQ tests are given several options to have the problems corrected before the soundproofing work begins. No federal money is available for remedial work on preexisting conditions; fixing the problems is the homeowner's responsibility. All appliances have to produce less than 100 PPM CO, flues must be clear, correctly sized, and drafting normally, and appliances have to vent properly even under worst-case depressurization. Once homeowners have brought their homes up to these standards, soundproofing can begin.

So far, the test procedures have unveiled a surprising number and variety of indoor air quality problems--88% of the homes tested were found to have IAQ problems. According to CEE's Bohac, The IAQ evaluations have produced the most comprehensive residential database ever to be recorded for appliance venting performance and CO production.

For the 100 CO evaluations tabulated through 1997, the findings are surprising. Of the natural gas ranges, 52% produced more than 100 ppm CO, as did 5% of the water heaters and 11% of the furnaces. Investigators attributed these failures to appliances that were out of tune or in need of cleaning and to burners that were overfiring from excessive gas pressure. Often, CO was only present under backdraft conditions. There was also spillage caused by flues that were blocked or too small for the ratings of the appliances they were to vent; inadequate supplies of combustion air; and backdrafting due to cold exterior chimneys, atmospheric conditions, and other drafting problems.

According to Bohac, the results may have implications nationwide. This work could be used to refine the national vent system design recommendations, vent performance test methods, vent draft pressure standards, and house depressurization limits, he says.

Once the sound retrofit is done, the contractors repeat the worst-case depressurization test and check house tightness. If spillage seems likely, the house is provided with a variety of vent system improvements.

--Zolton Cohen

Zolton Cohen is a home inspector and journalist in Kalamazoo, Michigan. He also hosts an on-line forum for home questions at


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