Installing Heat and Sound Insulation By Jim Clark (The Hot Rod MD)

by Q2Digital Q2Digital

The exhaust on my roadster is routed close to the floorboards creating a potential heat problem. This is not that big a deal in an open car but a lot of heat against the underside is still undesirable. Padding under the carpet would cut down on this, but a better solution is the application of a thermal-insulating heat barrier like HushMat.

In the past I had a bad experience with exhaust heat against the floorboard of a 1970 Ford van that demonstrates the need for this type of installation. Tom McMullen and I were traveling from L.A. to Peoria, IL to cover the opening of a new AEE Choppers dealership and chopper gathering for "Street Chopper” magazine. We loaded two choppers in the back of a van along with our clothes and camera gear. The muffler on the van was located close to the floor on the right side next to the slider-door creating a hot spot on the bare metal floorboard. We placed our luggage, consisting of two brown paper grocery bags containing our change of clothes, right over the spot. At the time we were not aware of the fact that Tom's wife Rose had left frozen chicken necks in the bottom of the bag when she packed his clothes in them.

The frozen chicken necks were for feeding Tom's pet cougars and she had forgotten to remove them from the bag after returning from shopping. We placed them in the van right above the hot spot where they began slowly thawing out. At first we thought some kind of dead critter was stuck up against the exhaust or hot engine creating a foul odor. We checked underneath the van but found nothing. Finally, as we were driving through the night in the middle of Kansas, we couldn’t take the smell anymore and decided to pull over. We searched the van until we found the source of the awful stench. When Tom lifted the bag the wet bottom of the bag tore loose dropping the chicken necks on the ground. They had thawed and started decomposing over the hot spot. Once we removed them we were able to continue on our trip.

I don't anticipate any long high-speed runs like that in the roadster, but expect the Magna-Flows mounted close to the floorboard will give off a fair amount of heat. To combat this I installed the sound deadening and thermal insulation material HushMat Ultra on the firewall, floorboards and interior surfaces of the body. It's an adhesive-backed foil that sticks tenaciously to most any surface reducing thermal transfer by over 400 percent. One layer can reduce firewall heat by over 40 percent. It forms well around irregular surfaces and changes the hollow sound of sheetmetal to a solid "thunk". The sound attenuating features are not as noticeable in an open car but the harmonic drivetrain noises are not as readily transferred to the occupants.

On the firewall I applied Silencer Megabond over the HushMat Ultra, to absorb engine noise instead of Jute padding that was commonly used for this purpose. It has an adhesive backing that sticks to any surface and forms well around irregular shapes. It can also be used on the floor under carpet, on door panels and under headliners. My upholsterer will add padding beneath the carpet before he installs it. Before he does that I will secure the wires that run to the rear of the vehicle along the floor inside the body with Quiet Tape. It sticks to nearly any surface and will prevent the wires from moving around or being damaged beneath the carpet.

There are a number of similar products available that are either peel-and-stick or mixed and sprayed on but I chose HushMat because it is the one used most by the OEM carmakers and fares the best in the independent tests that I have seen. The accompanying photos show my own installation process. It was not difficult but required some careful planning and measuring before cutting the material. In most cases I made patterns using the backing material from the HushMat. Large flat areas where full sheets were used did not need this, but for small irregular areas this was necessary.

This installation may seem like overkill in a roadster but the benefits far outweigh the cost and small amount of time needed to complete the job. My 80 year-old hot rod will not provide the quiet ride of modern-day Detroit iron, though I expect it to be much quieter and cooler than the other old cars like this that and I have owned.

HushMat Ultra Sound Deadening & Thermal Insulation material is a butyl rubber constrained layer (foil backed) damping material that’s just below 1/8" thick & 0.47 pounds per square foot.  It forms & contours easily to uneven surfaces with no surface preparation or cleaning required other than vacuuming any dirt and wiping with a damp rag.  It reduces thermal transfer by over 400% and is rated to perform up to 400 degrees Fahrenheit.

Silencer Megabond Sound absorbing & thermal insulating foam is 100% EPDM foam rubber with an aggressive butyl-based pressure sensitive adhesive.  It can be applied over HushMat Ultra or directly to the floor under carpet, door panels and headliner.  It absorbs airborne and wind noise.   It is designed to allow less than 0.5% water absorption and is rated to perform up to 300 degrees Fahrenheit.

Silencer Megabond foam is available in three thicknesses.  The thickest, 1/2-inch, is for areas like the firewall and the others for places not needing as much sound-deadening effect.

Quiet Tape is a soft, pliable foam tape for universal application and works well at holding wires in place behind the dash or beneath carpeting where it routes to the rear of the vehicle.

Ultra H2O damping and seam sealing water-based paste is used as a sound-deadening material injected between panels like the decklid or doors where access to applying HushMat Ultra is not practical.  A standard silicone application tool is used for the dispensing of Ultra H2O.  You apply a bead of Ultra H-2-O between the trunklid frame and the outer skin – ensure that you have good contact on both surfaces with the H-2-O.

These basic tools should be all that is needed for the installation.  Wood chisel (second from left) has a tapered end that made it possible to smooth the edges of the HushMat Ultra in areas where the roller or my fingers could not reach.  You will also need a tape measure and marking pen or pencil to mark the cutting lines.

Cardboard can be used to make patterns.  A permanent marker is good for tracing the outline of the pattern on the HushMat Ultra.

After you have applied a few sheets of the HushMat Ultra you will have some backing paper to use for patterns.  The backing paper is flexible so that it can be formed around irregular shapes and stiff enough to hold a crease providing cutting lines.

A razor knife can be used to cut the material but I found that it was easier to do with scissors. Don’t remove the backing paper before cutting, as this will make it stick to everything, including the scissors when you begin cutting.

My firewall has a recess that measures exactly the width of one standard sheet (12-inches across including the angled sides) so I marked the center and peeled back the backing paper a bit and stuck it to the top of the recess.  I then continued peeling back the paper and smoothing out the HushMat Ultra to the face of the firewall recess.  Then folded it around the sides and trimmed away the excess length and overlap at the corners.

A pattern was made for the right side using a piece of backing paper cut to fit.

The HushMat Ultra sticks tenaciously to just about anything that it touches, including the backing paper, so I found it easier to remove the backing paper and reapply it loosely.  Cutting it into smaller strips made it easier to expose a small area and smooth it in place before exposing another segment.

The pattern was flipped over to mark the sheet for the other side of the firewall.  Gap in the center was filled with the excess left after trimming the first sheet used for the center projection.  Small relief was cut to clear the throttle pedal linkage when the center covering was folded over.

Patterns were made from backing paper to fill the areas behind both kick panels.  It was done in two pieces to span the support running through the area.

Underside of the cowl was covered using two sheets trimmed to follow the irregular contours. First patterns were made because the area is so irregular in shape and contour.

Here is the completed installation of HushMat Ultra to the cowl and firewall area.

Next I applied HushMat Ultra in full sheets to the front inside of the quarter panels on both the right and left side.  Then cut a full sheet to follow the contours of the body above the wheelwells.

Use a full sheet wherever possible to maximize the process with the minimal amount of waste when trimming to fit.

Because of the irregular contours of this area making patterns is necessary.  There is no square corner so I lined up the longest straight edge, then scored and cut the pattern to fit.

The pattern was transferred to the sheet and cut out with scissors.  It looks like there is a lot of clearance behind that upright but the large sheet will stick to anything it contacts so removing the backing and reapplying it loosely will make it easier to apply with minimal wrinkles.

The rest of the wheelwell area had to be covered with pieces cut to fit after making patterns.  I chose to cover the area completely but you could leave a little gap around the edges the way that OEM automakers do.  There are a number of seams between the pieces but they are not a problem as the HushMat Ultra sticks tenaciously.

Flat areas like this and the rear floorboards are pretty easy to cover.  I removed the taillights to place the HushMat Ultra sheet, and then cut away the material covering the opening before reinstalling them.

The body panel behind the seat has a hinge bracket that is almost touching the panel.  Feeding the sheet under the hinge bracket and removing the backing paper was very difficult because it would stick and not slide beneath it.

The piece on the left shows how I removed the backing paper, cut it in strips and folded it creating a hinge to feed it behind a close obstruction without it sticking where I didn’t want it to. The piece on the right is how I cut the piece in half and moved the backing paper in so the edges could be placed, then the sheet smoothed toward the center just leaving a small seam where they met.

I left the flat floor area until last because it can be done with full sheets and minimal trimming. Small stiffening recesses in the floorboard can be pressed in using a finger because the sheet has flexibility to mold around contours.  The deep V-shaped channel crossing the floor had to be filled by smoothing the sheet down on one side and up the other because the HushMat Ultra backing will stretch quite far but the foil will tear if you try to stretch it into something this deep.

If you are careful when placing a sheet there will not be a lot of wrinkles or air bubbles beneath them.  If you leave any, the bubbles can be punctured with a knife tip and then rolled out with a roller like this one made for smoothing seams on wallpaper.

Here is the finished installation of the HushMat Ultra.  Any holes that need to be opened can be pressed down with a fingertip and cut out with a razor knife.

Silencer Megabond foam (1/2-inch) was the next item to install. The sheets are the same size as the HushMat Ultra so I was able to cover the firewall repeating the same procedures. The only difference in the installation on the recess was in not having to cut the top corners because the flexibility of the foam allowed it to be formed around them.

The old pattern used to apply the HushMat Ultra worked well with just a small amount of trimming to allow for the extra thickness of the Silencer Megabond.

The foam is easier to mark by tracing the outline of the pattern onto the backing paper because the foam doesn’t mark very easily.

I had the best results cutting the foam with scissors.  A razor knife will work but leave a more ragged edge.

Foam is applied the same way as the HushMat Ultra and sticks very well.

The combination of HushMat Ultra and Silencer Megabond should cut down the transmission of heat and engine noise through the firewall.  Carpeting will be applied over the foam completing the installation.

Hushmat Installation By Rick Webster

by Q2Digital Q2Digital

Project Buckshot, our 1975 Ford Bronco that is undergoing a complete frame-off restoration / transformation, is coming along nicely. The folks at Midlife Classics have completed the body work and applied paint to the body. They also coated the interior, fender wells and underbelly with POR-15 (an incredibly tough, rust stopping paint material). With reassembly of the rig right around the corner, we needed to make a tough decision for the interior finish. Do we use spray-in bed liner, or go with carpet?

Buckshot will be a daily driver for the owner, seeing a lot of highway miles and traffic time on surface streets, in addition to time on the trail. Since the owner wants a relatively comfortable ride to be able to drive it across country to his favorite wheelin’ spots, we decided to up the comfort levels and go with carpet. Instead of installing carpet directly onto the painted metal body, we decided to install a heat / sound dampening mat first – this way the owner could hear Boy George and Backstreet Boys piped through the speakers more clearly. Project Buckshot will also have its original engine transplanted with a 400+ horsepower monster mill and an automatic transmission that will surely create more heat than the stock 302 that came out of it.

We needed material that would not only deaden sound, but also reduce heat in the interior too, since it will be wheeled in New Mexico, Arizona and other scorching climates. After looking at several manufacturers of sound deadening / heat reducing mat material, we landed on Hushmat for a variety of reasons. Hushmat outperforms other competitors in a few key areas such as; ease of installation, better heat reduction, no special surface prep needed, it passed the stringent approval process for several OEM manufacturers, and it’s made in the USA. Here are a few other key features of Hushmat:

Eliminates road noise and vibration.

Reduces heat up to 40%.

Automotive OEM specified and approved!

HushMat Ultra requires no pre-cleaning of the application surface.

No more acetone or alcohol surface preparation.

HushMat Ultra requires no heat guns or messy glue to apply.

One-Step application with HushMat Ultra—simply Peel and Stick!

Apply to door skin, door frame and door trim panel.

Apply to trunk floor and trunk lid.

Apply to floor from firewall to rear deck.

Apply to Inside of roof skin (yes, you can install it upside down and its guaranteed to stick).

Proven to perform from -30° F to 400° F.

Hushmat Installation

Time to install: 5 hours

Tools Needed: Scissors and/or razor blade knife (a roller wheel is optional and nice to have, but not needed)

Difficulty: ½ wrench

We began our installation by wiping out the interior of the Bronco. A layer of dust had accumulated from the color sanding that was done. However, Hushmat states that no cleaning or preparation of the area is needed. In fact, it can be installed (and continue to stick to) metal that is covered in oil and grease. Nonetheless, we cleaned the interior with a bit of water and a rag then let dry.

Installation of Hushmat couldn’t be easier. Simply peel the non-stick paper off of the back and press into place. We started at the rear of the truck where things are relatively flat and square, and worked our way forward. We found it easiest to peel back just a portion of the non-stick paper and apply it like a sticker transfer sticker.

As we worked towards the cab of the Bronco, we installed the Hushmat by cutting pieces with a pair of regular scissors (it cuts very easily) to for the shapes of the transmission tunnel more easily. When we covered a bolt hole in the Bronco that needed to remain, we simply pushed a Phillips screwdriver through it, or cut it out with a razor blade knife.

We continued to cover the rest of the interior, including areas such as the fender well humps and the vertical portions of the fender too.

The Verdict

Obviously, Buckshot isn’t in a drivable condition yet, but we noticed an immediate difference after installation, just by knocking on the body of the truck. What used to be a resonating clang sound is now replaced with a soft, muffled, quiet thud sound.

Installation of Hushmat was incredibly easy – far easier than we anticipated it to be. It’s sticky enough to hold it firmly in place (even upside down on a headliner), but not so sticky that you can’t peel it off if you start to install it and decide to change position. It’s very flexible and will tuck nicely into corners and mold around curves just as easily too. It’s also very easy to cut even with cheap scissors or a razor blade knife and it will not leave a nasty residue on your tools or your vehicle.

We found that when pushing it into very tight corners, the aluminum-like skin would tear slightly. We would prefer a slightly thicker, more durable aluminum skin on Hushmat, but we know that it will not affect performance in any way.

Overall, the Hushmat sound deadening, heat reflection system seems to work incredibly well and installation was so easy a caveman could do it. It does a great job of deadening sound vibrations, and we will follow up on this article after Buckshot is on the road and we can report on how well it reduces road and engine noise.


15032 W. 117th Street

Olathe, Kansas 66062

Phone (913) 599-2600

Fax (913) 599-2607

Web: www.hushmat.com

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