HushMat Cabin Heat and Noise Reduction

[Charles W.]

During the summer, I installed the HushMat product under the front carpet in my '72 convertible. I'm really pleased with the cabin heat reduction and the sound dampening qualities. I'm now planning to install under the rear carpet and perhaps in the doors. I've read on this forum where others have installed in the doors. Am I correct to presume that the material is actually installed on the back side of the door panel? Does this alter the door panel fitment?

Thanks

[Ed S.]

Re: HushMat Cabin Heat and Noise Reduction

Charles,
I applied "Dynamat" in the doors of my '64 convertible. Even though your car is a 72, for this application I don't think your results would be any different than what I experienced. I applied the Dynamat to the back side of the exterior wall of both doors - top to bottom. This stuff is only about 1/8 of an inch thick but it is really - really - sticky. I suppose you could put it on the interior surface and it probably would not interfere with the fit of the door panel or other components. But.... If you ever had to get into the door to fix something you would have a real mess on your hands - this stuff does not come off easy. As for noise mitigation - it a convertible - zero. There is no noticeable difference. What does sound a lot different is the sound of the door closing - it sounds a lot better, very solid - it just sounds good if you know what I mean. I had my door windows out for repairs - that is when I installed the Dynamat - I suppose you could do it without removing the glass. As far as applying the material to the back side of the door panel - not sure that would do much except perhaps provide some thermal insulation for when the car is all buttoned up but again - its a leaky convertible - how much heat do you lose through the doors?

[Mark E.]

Re: HushMat Cabin Heat and Noise Reduction

Dynamat (a competing product) claims that installing it on the backside of outer the door skin will provide a more solid sound when closing, as Ed shared. They also say it can be applied to the door structure just behind the door panel to replace or supplement the original plastic moisture barrier. I presume installing it in either location in the door should help reduce noise a bit from the outside, but that's apparently not Ed's experience.

HushMat may be a similar product(?), but before using it as a moisture barrier, make sure it's designed for that purpose and doesn't absorb moisture.

I'm currently installing Dynamat and Dynaliner on the floors and firewall in an attempt to reduce radiant heat. Sound deadening is a side benefit, but noise isn't an issue for me (it's a Corvette after all!). Until I'm finished, the jury is still out if this stuff makes a difference or not. Radiant heat coming through the doors isn't a problem so I'm undecided about installing it there, although I do like the idea of the door sounding solid when closing. If I did install it as a moisture barrier, I plan to cover the entire door structure, similar to the coverage of the original plastic barrier. If access to something inside the door is needed later, Dynamat can be easily cut to uncover the access holes or bolts in the door frame.

As an aside, Al Knoch told me that since their reproduction door panels use a plastic, ABS type of backing, a moisture barrier is not necessary. (The originals are made from some sort of fiber board material that absorbs moisture.)

[Ed S.]

Re: HushMat Cabin Heat and Noise Reduction

If you do decide to apply Dynamat to the interior of the door be careful not to cover up the drain holes at the bottom of the door. There are 4 to 6 drain holes, long, narrow "slots" at the very bottom of the door. Also, installing this stuff inside the door is not that easy - it instantly sticks to anything it comes in contact with. Installing large pieces is difficult. I found cutting it into smaller pieces, the largest about 12 in by 18 in works. This stuff overlaps nicely and does not have to be one continuous piece to do its thing.

[Mark E.]

Re: HushMat Cabin Heat and Noise Reduction

That's a good tip. I was wondering how to apply it to the door skin with the window still installed. To achieve a more solid sound, Dynamat says only partial surface coverage is needed (I think 30%?). How much did you cover?

[Ed S.]

Re: HushMat Cabin Heat and Noise Reduction

Mark, I covered probably 95% of the outer door surface. I never saw the product literature that stated just partial coverage is needed - 30% seems low to me. I bought a package of "Dynamat Extreme" that contained 4 pieces, each 12 inches by 36 inches. I had about 1 square foot left over. Don't expect miracles - door closing definitely sounds a good bit more solid but it's not going to sound like a new Mercedes Benz sedan if yo know what I mean. Am I happy with it, yes - was it worth it, I think so.

[Mark E.]

Re: HushMat Cabin Heat and Noise Reduction

Apparently only partial coverage is needed to reduce panel vibration and achieve a solid sounding door. I believe most or all of the panel should be covered if you want to achieve noise or heat abatement.

[Charles W.]

Re: HushMat Cabin Heat and Noise Reduction

Ed, thanks for your input. If you had it to do over, would you still install in the doors of your convertible?

[Charles W.]

Re: HushMat Cabin Heat and Noise Reduction

Thanks to all of you for the responses and all the good information. I will probably just install under the rear carpet and skip the doors. My primary goal was to reduce radiant heat. The sound dampening was just a side benefit.

Chuck

[Mark E.]

Re: HushMat Cabin Heat and Noise Reduction

That's what I'm leaning towards also.

[Ed S.]

Re: HushMat Cabin Heat and Noise Reduction

One thing that I did not mention and might be important to some is that if you put it in the doors and then look down in the door cavity when the window is rolled down you can see the Dynamat applied to the outer door skin. I haven't had my car judged, and probably won't, but I suspect that the presence of any after market material inside the doors would result in a point deduction. Even if a judge didn't actually look for it, I also suspect any judge worth his bow-tie would notice something different the first time he (or she) shut a door. The sound difference is very noticeable.

[Bruce B.]

Re: HushMat Cabin Heat and Noise Reduction

With Dynamat about 60 % to80% coverage on the inner side of the door skin is sufficient.
No need to cover the bottom inside of the door so drain holes are not a issue.
On my 65 coupe I also installed on the inside surface of the roof. It made a major difference in resonance.
As with the doors if you tap on the outside surface you get a thud, not a tinny sound after installation.
I have Dynamat installed in my 65 coupe, my 62 Hardtop car and my 57 convertible.
Great reduction in noise and heat.
Dynamat also comes in Black and it is MADE IN THE USA.

[Mark E.]

Re: HushMat Cabin Heat and Noise Reduction

One thing that I did not mention and might be important to some is that if you put it in the doors and then look down in the door cavity when the window is rolled down you can see the Dynamat applied to the outer door skin. I haven't had my car judged, and probably won't, but I suspect that the presence of any after market material inside the doors would result in a point deduction. Even if a judge didn't actually look for it, I also suspect any judge worth his bow-tie would notice something different the first time he (or she) shut a door. The sound difference is very noticeable.

Good point. It may also be detected if the ashtray is removed or around the carpet slits for the seat bracket.