Sound Deadening

**manic** · 29th April 2013, 08:27 PM

Originally Posted by Dougal

The thermal conductivity of materials is measured as a K value. Watts x metre. Which is actually w per metre squared per metre thickness.
Lower values are better insulators.
From there, to account for insulating thickness, you divide the K value by the thickness and that gives you watts per square metre (u) of material per degree of heat difference. The often referenced R value is 1/U. Lower U (hence higher R) are better insulators.

K value for bitumen, 0.17. Thermal Conductivity of some common Materials and Gases
K value for EVA foam, 0.033 Polyethylene and EVA Foams

So for equal thickness, EVA foam is ~5 times better.
But we aren't talking equal thickness, we're comparing 1mm of bitumen to at least 6mm of EVA foam.
Bitumen: 0.17/0.001 = 170 watts per degree of heat difference per m^2.
EVA Foam: 0.033/0.006 = 5.5 watts per degree of heat difference per m^2.

As a thermal insulator, 6mm of EVA foam is (170/5.5 =) 31 times better than 1mm of bitumen.

With EVA foam you'd have saved heaps, had a quieter vehicle and a far cooler one.

BTW, you don't want to bond your insulating materials as that greatly reduces the thermal and acoustic properties. Every air gap is worth an R value (1/u value) of ~0.2 for thermal insulation.

I thought the reflective nature of the aluminum skin made the difference

. If you mange to line a bulkhead with camping mat - well done.

With bitumen backed reflective foil on the outside of the floor/seat.b/firewall it DOES keep the heat out very well.

If you got yourself two upturned boxes and placed them near a fire with a thermometer under each - one covered in foil faced bitumen (say dynamat) and the other with just equal thickness foam - which box is going to heat up quicker?

**granno** · 29th April 2013, 08:44 PM

Originally Posted by manic

I thought the reflective nature of the aluminum skin made the difference

. If you mange to line a bulkhead with camping mat - well done.

With bitumen backed reflective foil on the outside of the floor/seat.b/firewall it DOES keep the heat out very well.

If you got yourself two upturned boxes and placed them near a fire with a thermometer under each - one covered in foil faced bitumen (say dynamat) and the other with just equal thickness foam - which box is going to heat up quicker?

I think that dynamat should be installed on the outside of the panels for that exact same reason. Installing it on the inside actually absorbs heat. It will stop the resonating of the material whatever side it is on. If installed on the outside it would aide in reflecting for sure but the air gap is the secret for heat.

**Dougal** · 30th April 2013, 08:06 AM

Originally Posted by manic

I thought the reflective nature of the aluminum skin made the difference

. If you mange to line a bulkhead with camping mat - well done.

With bitumen backed reflective foil on the outside of the floor/seat.b/firewall it DOES keep the heat out very well.

If you got yourself two upturned boxes and placed them near a fire with a thermometer under each - one covered in foil faced bitumen (say dynamat) and the other with just equal thickness foam - which box is going to heat up quicker?

For the shiney side to work, it has to face a radiant heat-source (the sun, hot exhaust etc).
So on the top of your roof it'll be nice. On the inside it'll make no difference.

**Loubrey** · 30th April 2013, 12:00 PM

Looking at what that stuff costs you might as well go for the bespoke Exmoor Trim rubber matting I installed... (see my post on rubber matting system).

I get just about no heat transfer from the floor, seat box and tunnel (especially on the hand brake lever) and iPhone Db tests shows a 5 Db drop in the Puma's cabin noise since installing it.

Reading what some guys spend on this sound deadening and heat proofing exercises makes the $700 odd delivered price from the UK look like an absolute bargain.

The bitumen backed foil stuff on the doors and roof does sound like an option though...

Cheers,

Lou

**manic** · 30th April 2013, 12:38 PM

Originally Posted by Dougal

For the shiney side to work, it has to face a radiant heat-source (the sun, hot exhaust etc).
So on the top of your roof it'll be nice. On the inside it'll make no difference.

Sorry Dougal but this may be a case of a theory disproved in practice. Compared to a bare aluminuim roof panel it does make a significant difference even when inside of roof covered - as stated before. Burnt fingers to touch warm.

I now have a fiberglass headliner with foam clamped between it and the bitumen foil lined roof. Perhaps I would have good results with just foam stuffed under the headliner but at the time I had no headliner just the roofs thin sheet of aluminum above my head.

I got a cheap batch of bitumen/foil and it was well worth covering the entire inside of the roof with the stuff. It took very little time and effort to put up and it reduced heat radiation coming off the roof panels - significantly!

I would do it again, the second road trip to same region at same time of year was much improved with a cool/warm foiled roof compared to the exposed red hot radiator roof I had the year before.

**Dougal** · 30th April 2013, 01:31 PM

Originally Posted by manic

Sorry Dougal but this may be a case of a theory disproved in practice. Compared to a bare aluminuim roof panel it does make a significant difference even when inside of roof covered - as stated before. Burnt fingers to touch warm.

I have already shown what the insulation value of bitumen is. The insulation value of the foil backing is damn near zero.
Shiney foil is only good for reflecting heat from a radiant source. To do that it has to face the sun or a hot exhaust.

Foil inside does nothing.

The best result would be to copy landrovers safari roof. Put another layer on top with a vented air-gap.

The people who think they disproved theory in practice, normally don't understand the theory.

**Bush65** · 30th April 2013, 01:39 PM

Originally Posted by manic

Sorry Dougal but this may be a case of a theory disproved in practice. Compared to a bare aluminuim roof panel it does make a significant difference even when inside of roof covered - as stated before. Burnt fingers to touch warm.

...

I'm sorry, you are talking of one experiment about heat conduction to a finger in contact with the under surface of your roof.

You have failed to repeat the same experiment with the other material.

Conduction to your finger at the contact point has little to do with heat radiated from the same under surface into the cabin interior.

So you can't say in any shape or form that you have remotely disproven the theory.

Go and write 100 times on the blackboard, I shall not .......

**manic** · 30th April 2013, 01:56 PM

Originally Posted by Dougal

I have already shown what the insulation value of bitumen is. The insulation value of the foil backing is damn near zero.
Shiney foil is only good for reflecting heat from a radiant source. To do that it has to face the sun or a hot exhaust.

Foil inside does nothing.

The best result would be to copy landrovers safari roof. Put another layer on top with a vented air-gap.

The people who think they disproved theory in practice, normally don't understand the theory.

I am not disputing the figures on the material or the proven theory/facts on best practices for insulation which you are aware of. I am not saying all you need is some bitumen or that it is the best option for heat insulation.

The thing is though, a bit/alu lined roof is cooler than a bare roof so I cannot agree that lining the inside of the roof with foiled bitumen does 'nothing' to stop heat transfer. That is simply not true. The bitumen has some insulation value as does the reflective nature of the foil even in its least effective orientation.

You may refuse to believe that full coverage of a land rover roof with this stuff makes a difference but I know it does because I have sat for long hours with my head a few inches from exposed roof with and without the lining.

**manic** · 30th April 2013, 01:58 PM

Originally Posted by Bush65

So you can't say in any shape or form that you have remotely disproven the theory.

I'm talking about his theory about my roof not being any cooler after I lined it!

**Dougal** · 30th April 2013, 02:05 PM

Originally Posted by manic

The thing is though, a bit/alu lined roof is cooler than a bare roof

****, really?

Originally Posted by manic

so I cannot agree that lining the inside of the roof with foiled bitumen does 'nothing' to stop heat transfer. That is simply not true. The bitumen has some insulation value as does the reflective nature of the foil even in its least effective orientation.

The bit in bold above, No-one said that, You made it up.

The insulation value of a layer of foil in full contact is so small it can be completely ignored.

Originally Posted by manic

You may refuse to believe that full coverage of a land rover roof with this stuff makes a difference but I know it does because I have sat for long hours with my head a few inches from exposed roof with and without the lining.

Again, you're making stuff up. I have never claimed or believed it won't make a difference. I have said it is a terrible choice (both cost and effectiveness) for such an application.

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