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Heat barrier for roof
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Kevikev94596
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PostPosted: Mon Sep 29, 2014 9:39 am    Post subject: Heat barrier for roof Reply with quote

I do not want to pay for dynamat, but need a product that I can use under the headliner to act as a heat barrier. I do not want something that is going to make my bug smell like tar. Any suggestions? I am going to use fatmat under the carpet and on the door panels for sound barrier. Will this also work as a heat barrier on the roof?
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raygreenwood
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PostPosted: Mon Sep 29, 2014 10:15 am    Post subject: Reply with quote

You need to think about what is going on here first. I deal with heat transfer issues in my line of work every day...so what I am going to say may sound stupid but I am reducing it to not get into a long technical discussion.

1. The roof gets hot from absorbing a wide range of sunlight spectra....from IR in the slow end (infrared) to UV in the fast end of the spectrum. The roof metal conducts that heat and its radiated to the inside.

2. So knowing those two mechanisms you can choose which to attack first to stop the heat .

You cannot fully stop conduction. Even a closed cell foam applied as a blocker to prevent the metal from radiating that absorbed heat at you.... will eventually absorb enough heat to saturate and then that block/sheet of foam itself becomes a large mass that will keep radiating heat from itself long after the sun goes down. i have been there and done that in many situations.

3. The first line of defense is to deflect as much heat away from the roof as possible. VW already knew this...which is why you have two toned paint jobs with virtually all of them having a white or light colored roof. The lighter the better. A white roof will not absorb nearly as much heat as ANY other color even a light beige or yellow.
Also...added to this....a very high gloss roof will reflect away upwards to another 25-30% of light spectrum...most especially UV and Infrared.

So...start out with cooler roof.

4. Use reflective materials on the inside to reflect as much radiant heat as possible back to the roof and out of the interior.

However, do not attach a reflective foil directly to the metal...because then it just becomes part of the metal mass. It needs to have a gap.

Usually foil attached to a THIN closed cell foam makes a good combination product. Yes....eventually the closed cell foam will saturate, but the reflective foil laminated to it will keep it from easily radiating inward.

Look for products that are ONLY designed for heat blocking...not for sound blocking. Its a difference in what gas is used to make the foam and what the plastic base is. Many products that are superb for absorbing sound transmission are not good for blocking heat transmission.

Just some thoughts. Ray
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Kevikev94596
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PostPosted: Mon Sep 29, 2014 10:53 am    Post subject: Reply with quote

Very insightful! Thanks Ray! I just painted the car white, so step one is complete. Now I just need to find the right product a you described
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eyetzr Premium Member
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PostPosted: Mon Sep 29, 2014 12:57 pm    Post subject: Reply with quote

there was a post from 67bagged (Ithink) & he used something on his roof. Tinfoil like product (sounds like something Ray was describing.
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marklaken
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PostPosted: Mon Sep 29, 2014 1:39 pm    Post subject: Reply with quote

graft in a sunroof Smile

I used secondskin (a competitor to dynamat - it's a tad cheaper and seems really high quality. Still not as cool as a sunroof, though Smile
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theKbStockpiler
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PostPosted: Mon Sep 29, 2014 7:51 pm    Post subject: Reply with quote

I was considering some way to keep a vdub cool without A/C. My first idea was to use a roof rack with a panel on it so it would work like an umbrella. This kills the look of the car but I still want to do it. This thread got me thinking that maybe bubble wrap or construction foam might be able to be affixed to the ceiling under the headliner. This might also be a fire hazard. Shocked
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abritinthebay
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PostPosted: Wed Oct 08, 2014 1:14 pm    Post subject: Reply with quote

Second Skin sells a bunch of this stuff.

Honestly? If you want it to actually work and not be crap you'll be paying decent money for it. Dynamat is kinda old school and overpriced though... so agreed on skipping that.

Second Skin has their Heat Wave Pro which is exactly the kind of product you want for this. Bonus - it also helps filter out some sound too. It's a double foil layered insulation product. Really nice.

Now ideally you'd add this over some kind of noise barrier (which a usually some kind of butyl rubber if they are any good, not tar crap that doesn't work) as those also have a solid thermal property. Their Damplifier or Damplifier Pro is excellent for this.

In fact I'd go as far as to say get the Damplifier FIRST because it'll work well as a thermal insulator (which is what you want) and will ALSO work as a great CLD noise solution.

Then, when you have the budget for it, go and get the Heat Wave Pro to add to it (spray glue is all you need) and you'll have an even better roof done right.
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Kafer_Mike
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PostPosted: Wed Oct 08, 2014 1:56 pm    Post subject: Reply with quote

I installed B-Quiet (http://www.b-quiet.com/ultimate.html) Ultimate on my Beetle ~6 years ago. Much cheaper than Dynamat. A 50' roll did the floors, doors, roof (under the headliner) and parcel tray. It's butyl-based so I didn't have an issue with "tar smell" and haven't had any issues with it lifting or dropping.
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