Carpet's Hidden Benefits

• By Julie Sturgeon
• 01/01/06

The Carpet and Rug Institute (CRI) documents a rise in the use of carpet at colleges and universities in recent years — but the driving forces behind this popularity surprise most. Werner Braun, president of CRI in Dalton, Ga., credits carpet’s ergonomic comfort and noise reduction properties for the upsurge.

The numbers certainly back his claims. For instance, Alan Hedge, Ph.D., a professor in the Department of Design and Environmental Analysis at Cornell University, cites the fact that studies show the human heart’s beats per minute are higher after two hours of standing on a concrete floor versus carpet. His white papers also point out that standing on a hard surface increases shank swelling, lower leg electromyography (EMB) activity and muscle fatigue.

“How many trade shows have you been to where you walk around for hours on a hard surface? A little of that and my back is just screaming,” Braun says.“You need cushioning, otherwise you end up with all kinds of discomfort.”

It turns out that cushioning offers an additional layer of protection most administrators overlook as well. CRI’s data shows that people are seven times less likely to fall on a carpet than a hard surface and 10 times less likely to sustain a serious injury during those unlucky times when they do. The studies are significant enough to prompt some insurance carriers to offer reduced premiums to facilities with carpeting.“If universities haven’t inquired about that, they ought to,” Braun adds.

The statistics are just as impressive when you flip to the acoustics page. For example, carpet provides up to a 70 percent reduction in ambient noise in an office or school setting and absorbs 10 times more airborne noise than any other flooring choices. Researchers love to cite a study that reveals students catch only three out of four spoken words in the classroom when educators don’t specify good noise reduction factors. Braun assures colleges those findings extend beyond the K-12 world. “It applies to large rooms, especially auditoriums, as well. We just built a new church here in Dalton, and they didn’t have enough funds to put the carpeting down right away. When our pastor gave the Sunday sermon, you left scratching your head trying to figure out exactly what he was saying,” Braun adds, from firsthand experience.

Specification Tips

Fortunately, comfort and noise reductions aren’t mutually exclusive — administrators automatically get both when they spec carpet in a building’s plans. But it’s still important to understand the jargon and use the correct measurements in the bid process to ensure the best bang for the buck, says Braun. From the CRI’s guidelines:

Density: One of the most important, and often most misunderstood, factors in carpeting, this index describes how much yarn is packed into a given volume. The larger the density value, the more compact the pile and the firmer the walking surface. Contractors commonly use average pile yarn density (APYD) numbers — determined by pile weight (specified in finished ounces per square yard), pile thickness or tuft height. The higher the APYD, the better the carpet’s performance. Commercial carpet normally exceeds 4500. High-traffic areas typically require an APYD over 6000.

Sound Transmission: Experts measure sound transmission between two reverberation rooms for at least 16 standard frequency bands. The sound transmission class (STC) rating condenses sound transmission information into a single number and is fairly accurate for human speech. But, as the CRI literature reminds, transmission through walls, floors and other barriers is much greater for low frequency sounds, so motors, fans or even music with a strong bass will emit a greater perceived sound than the STC indicates.

Impact Noise Rating: INR is a single-figure rating of the sound insulation provided by floor-ceiling assembly from an impact noise. Here the data relates to a minimum standard of zero, so a minus INR would be unsatisfactory. Rooms that rate a plus INR are considered superior.

Some studies will cite their impact noise rating as an impact installation class (IIC) number. The test procedure is the same, but IIC rates its results only in positive numbers. The larger the number, the greater the sound insulation, officials at CRI tell users to add 51 to the INR number if they wish to compare apples to apples.

But beyond a working familiarity with these terms, Braun suggests colleges and universities avoid over-specifying their carpet requirements. For instance, he says a 20-oz. base fiber — consistent with commercial carpet definitions — provides plenty of cushioning underfoot and adequate noise reduction.

“There is no question there is a point of diminishing return,” he points out. “Take a carpet with a 30-oz. weight and compare it to one with a 70-oz. base weight — I’d be hard pressed to say you could tell much difference between those.” On the other hand, choose the trendy European models that offer just a few ounces of fiber and everyone is likely to notice the difference.

“Think in terms of penetration of sound waves into a porous surface like carpet, and you’re on the right path,” Braun adds.