Radiant Barrier soft top insulation

Myself and 3 friends started a Radiant Barrier installation company in Austin a few years ago. The whole Idea behind radiant barrier is the use of reflective materials to reflect heat from a source instead of dampening it. To operate correctly, a radiant barrier has to meet a few guidelines.

I had noticed that the titanium shift knob in my NA got very very hot when I closed the car up, with windows rolled up. However, with the top down and the same shift knob in direct sunlight, it did not get anywhere near as warm. This indicated that the source of heat inside the car was radiant heat, instead of direct heat.

Also, obviously, if I held my hand near the fabric top, I could feel heat coming off of it for at least 2 inches. Theres no way an A/C unit can operate optimally with that happening.

Normal radiant barrier, i.e. the metallic foil with polyproylene mesh inside works wonderfully in attics, but if placed directly against a heat source, it acts as metal does, and simply transfers heat from one side to the other. When using radiant barrier in a location where it is necessary to have it touching the heat source, you have to have a space between the external and internal reflective foil to stop that heat transfer.

There is a very inexpensive water heater wrap available at home depot that is made of two layers of radiant, reflecive, material, separated by about 1/8 inch of plastic bubble wrap. We used this material against garage doors because, even though the inside touches the door directly, there will always be 1/8" of space between the inner and outer layers. In our tests, this reduced garage heat by a measurable average of 30%.

This is exactly what I did to my soft top and it is working awesomely! I can now hold my hand up towards my roof and feel no heat at all coming in through it!

I have no measurements, but I feel that my A/C is working better, cooling faster. And when I leave the car and go into a store, its not nearly as hot when I get back in!

The hardest part of this was finding an adhesive that would let me hold the barrier against the soft tops fabric, yet not be permanent. I found "outside" mounting tape to be perfect for this.

It is 100% not visible from outside, and does not look anywhere as ugly as id thought it would!

All told this mod cost $15.
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Plus they can't read your brainwaves now. Autocrossers have used that stuff to make covers to retain tire heat.

Interesting idea....can you easily drop the top with it in place?

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Originally Posted by sammm

Interesting idea....can you easily drop the top with it in place?

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Not as is. But Ive been thinking that a better way of installing it would be to use fabric adhesive to stick velcro pieces on the soft top frame bars, then cut a single sheet of barrier to fit the interior. you cold then stick it up there, and take it down very easily and store it in your trunk.

How does it fare when driving with the windows down?

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Originally Posted by OZMDD

How does it fare when driving with the windows down?

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everything stayed where it was supposed to stay. Mine is not firmly attached to my roof yet. Im just using the outdoor tape, and not much of it. Im sure that velcro would be much more secure, I just havent committed to sticking it on the roof yet.

There is space in a few places to slide the material between the support bars and roof so that you dont need any tape at all.

Another idea I had was to cut aluminum beams and use them to support the material by sliding each end between a bar and the roof. I just havent figured out how to do this without the ends causing soft top damage.