Keeping Your Interior Cooler And Quieter With Design Engineering Inc


At 118 degrees, the interior of the Cheyenne was a bit toasty. Hopefully, the DEI materials can help with that issue.

Have you ever really considered or thought about a downside to attending a car show? I know what you’re thinking, “is there really a downside to consider?” If you’re like me and live in Florida, there really is. For instance; after the awards are given out and you climb back into your car or truck to drive home, how high is the temperature of the vehicle’s interior that is now a pressure cooker?

The old carpeting - if you want to call it that. It seemed more like a fuzzy, felt-type material, and shredded as I tried to pull it out.

Let’s face it, you just parked your car on a slab of asphalt for several hours and let the sun do its best to try and melt the sheetmetal surrounding your interior. Even if your car has air conditioning, how long does it take to cool the inside of your ride? After experiencing this unpleasant scenario several times, I decided to do something about it. So, I reached out to the folks at Design Engineering Inc. (DEI) to see what my options were.


Boom Mat is a simple and effective way to eliminate low-frequency vibration noise. Simply trim to desired size, peel backer, and apply to a clean surface. The adhesive backing is unaffected by extreme hot and cold temperatures, and can be applied to horizontal, vertical, and inverted areas on metal, plastic, fiberglass, and most other automotive surfaces.

While heat is a big concern, the air conditioning will eventually lower the interior temperatures to less than steam-worthy. But, like many classic car owners, interior noise is something that I would also like to reduce in the Cheyenne. Let’s face it, having a conversation with my wife, while driving around town should not require her to yell at me – most times. So, the challenge before me was to not only reduce interior temperatures, but also, a lot of ambient noise created either outside, or by the truck itself that invariably resonate into the cab. Sounds easy enough.

You will not need to cover every square inch of the area. Typically, we recommend 25 to 50 percent coverage. – Tom Miller, DEI

Why Do This

According to the National Highway Traffic Safety Administration, when a car is left in the sun all day, it can result in dangerously hot interior temperatures. For instance, they say that if the outside temperature is around 80 degrees or above, the inside of a car can reach upwards of 172 degrees. I’m certain that is measured on a new, late-model car with a lot of sound deadening materials and insulation – while parked in the desert.

But, what happens inside a classic car without a lot of insulation? I actually put a thermometer in the cab of my truck while it was parked in the driveway before I installed any DEI product, and at mid-afternoon (2:00), it was screaming 118.5 degrees.

As far as noise, we’ve all heard the saying, “they don’t make ‘em like they used to,” and that true statement directly correlates to our classic rides. Let’s just take a look at the roof of any car or truck. That’s a big, smooth piece of sheetmetal. When you drive your car, that slab of solid sun blocker develops a resonance – or sound.


To replace the stuff that someone thought would make a good floor covering, I ordered a replacement cut-pile carpeting from Classic Industries. The Jute backing, heel pad, and dimmer switch grommet, assure factory style was reinstalled in the truck.

Sound, is a vibration that your ear converts to noise. If you happen to have various, metal-created resonances, the interior of your ride can get noisy while driving.  In the C10, while idling at a red light, the decibel meter was reading a healthy 82.4 dB. At 60 mph, with the cruise on, the reading was 90.1. To put that into perspective, a normal conversation is roughly 60dB.


We installed the Under Carpet Light – of all places – under the new carpeting, in areas where the factory-style Jute backing was not present.

The human ear has the distinct ability to interpret an enormous range of sound levels. But, we as humans need a way to correlate that range into something we understand – numbers. The way we identify sound levels, is by something we call a decibel. The decibel scale uses numbers to identify a certain sound level, but instead of a linear scale, a logarithmic scale is used. Most units of measurement are understood in a linear fashion. For example, everyone knows that 2 inches is twice as long as 1-inch, and 4 inches is twice as long as 2 inches. Position these numbers on a graph, and they would form a straight line.

When installing the carpet, a small awl or even a Phillips head screwdriver makes a good punch for making holes for things like seat belt bolts, and the start of the hole for the dimmer switch grommet.

But that’s not how decibel measurement works. Decibels are identified using a Logarithmic unit of measurement that increases in powers of 10. If you don’t remember logarithms from back in high school physics, here’s the gist of it: With logarithmic numbers, each additional unit multiplies the true value of the number exponentially. For example, +3dB = 2 times the power, +10dB = 10 times the power, and +60dB = 1,000,000 times the power.

With a logarithmic scale, a change between the two values is perceived on the basis of the ratio of the two values. In other words, a change from 1 to 2 (ratio of 1:2) would be perceived as the same amount of increase as a change from 4 to 8 (also a ratio of 1:2). But, what is a decibel? Zero decibels (0 dB) is the quietest sound audible to a healthy human ear. From there, every increase of 3 dB represents a doubling of sound intensity, or acoustic power.


The Cheyenne’s outer door skin – like most vehicles – is an expanse of metal. By adding Boom Mat to the inner side, the vibrations created while driving are significantly reduced. I folded the mat pieces in half to slide them through the small-ish opening from the inside of the door.

Now that we have the lesson out of the way, let’s get back to the situation we need to overcome. It doesn’t matter how good your stereo system, it must still overcome the ambient noise resonating into the interior. Have you ever noticed that the tunes get louder when you stop at a traffic light? That’s because, when you stop, the road noise created by movement drowns out some of the music’s natural frequencies. When you stop, so does some of the resonance. But, if you can reduce the intrusion of those unwanted vibrations, the desired sounds – like your stereo or chatty passenger – become more clear.


Once the Boom Mat is positioned, simply apply pressure to secure it. DEI has a convenient roller you can get, which makes it easy.

Keeping Your Cool… And Quiet

The folks at DEI have figured out that the best way to cut down interior noise is to cover expanses of metal surfaces with a product that will increase the metal’s density to lessen vibrations, or absorb sound waves altogether.

The first recommendation I received was to install Boom Mat to areas of the cab. This acoustic-dampening product works by absorbing the unwanted noise and sound waves. It filters the distortion caused by audio waves from both low and high decibel frequencies, vibrations, road rattle, and engine noise. “You will not need to cover every square inch of the area,” said Tom Miller of DEI. “Typically, we recommend 25 to 50 percent coverage.”

Once the sound issue was handled, it was on to the initiating reason for this upgrade, interior heat. DEI’s Under Carpet Lite is a 1/3-inch thick multi-layer, high tech composite material designed to be extremely flexible and easy to install. It delivers thermal insulation in a lightweight padding that lessens heat transfer. What we found, was the company’s Thermal and Acoustic Interior kit.


The roof of the C10 is already a double-wall construction, but I am not sure what insulation – if any – is between the two pieces of metal. By the way, that is not rust on the roof, the previous owner painted everything inside the cab black, and that is paint that came off the backside of the headliner.

This universal kit includes both Boom Mat, and the Under Carpet Lite material so you can cover the needed areas of your ride. The Boom Mat came in two different sizes, so it really is universal. You do not need to completely cover all metal areas with Boom Mat. The material is designed to add density to the metal, so adding it to the middle of flat areas is sufficient. In fact, DEI recommends 50-percent metal coverage. The Under Carpet Lite, however, the more area you can cover, the better.

Sticking To The Plan

First, before applying any of the DEI products, it is imperative that the floors and surfaces be as clean as possible, so the Boom Mat will properly adhere. This stuff sticks like there is no tomorrow, but a layer of dirt and heavy grit can stop adhesion. With a suitably clean surface it is time to begin placing the Boom Mat in the car.

DEI, interior

I ordered part number 050500 Thermal & Acoustic kit to use in the truck. This was just enough material for the C10. But, if you’re working on a vehicle with a larger interior – think Chevelle, Camaro, Nova, or Impala – kit number 050499 would give you more material.

I first covered a large portion of the floor. If you remember correctly, complete coverage is not necessary. I also installed Boom Mat to the inside of the doors, and the roof. After the Boom Mat was installed, Under Carpet Lite was then placed over that. I will say that during removal of the old carpet, things did not go quietly into that dark night. The carpet – if you want to call it that – was not an actual carpet. A previous owner had glued a thick, felt-like material to the floor, and it came out in shredded pieces. That prompted a visit to the Classic Industries website to find an actual carpet set for the truck. The Cheyenne’s factory carpet should have been a cut-pile, and the replacement from Classic Industries was just that. It looks correct for the truck, and was a damn sight better than the “material” that was previously glued to the floor.

When it came time to insulate above the headliner, DEI had just introduced a new material that we wanted to try – D-Mat. According to Mike Buca of DEI, “the Under Carpet Lite is a more dense and durable material that is less flexible, making it perfect for under carpets. The D-Mat is very lightweight, flexible, and can also be compressed. This makes it a much better choice for under headliners, inside doors and package trays. The performance is similar, but the UC lite does hold a small advantage over the D-Mat in performance.”

Was It Worth The Effort?

In a word, yes! Once the interior was put back together, I first parked the truck in the same location and measured the interior temperature at around the same time of day – 2:00 p.m. After the install, our interior temperatures dropped significantly to 97 degrees. I know what you’re thinking, 97 is still hot, but it’s nowhere near the 118 we experienced before the install. What, you were expecting Yeti-cooler like results? Unless you completely cover the interior structure – and that includes the glass – the sun is going to warm the inside of your car or truck. And, if you don’t think 21 degrees is much of a difference, go swimming in water that is 80 degrees, and then jump in a pool with water that is 59 degrees. I guarantee you’ll notice the difference. When it comes to the truck, I’ll take the 21-degree decrease in temperature. But, what about the noise levels?

DEI, interior

The Under Carpet Light (right), is more dense than the new D-Mat (left). But, both have their place when reducing heat and noise levels.

As previously mentioned, the before-install dB readings were 82.4 dB at idle, and at 60 mph with the cruise on, the reading was 90.1. After the install of the DEI materials, those numbers dropped to 80 and 85 respectively. That is significant, and it was immediately noticeable, as I did not need the radio volume as loud as before.

S0, the DEI materials did improve the interior of the Cheyenne, and I am certain it can also help your car or truck. Just contact Design Engineering Inc. and find out what it will take for you to improve your interior comfort.

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About the author

Randy Bolig

Randy Bolig has been working on cars, and involved in the hobby ever since he bought his first car when he was only 14 years old. His passion got him noticed by many locals, and he began to help them with their own vehicles.
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