Insulation installation

[MikeW]

I've been busy POR15'ing my floorpans and the work has progressed nicely. I've added some Dynamat and I'm ready to install some heat insulation that I picked up at Pep Boys called "thermo shield". I think it's similar to the stuff that places like MSA sell but this was only $20 for a 4'x6' roll. It's an insulation material bonded to aluminum on one side.

My question ... which side goes down? I'm assuming that the foil side goes down but the installation instructions only say to put in in place with adhesive.

[drunkenmaster]

Logically the foil side will face the heat source to reflect the radiant heat, but this means putting it underneath the car, not inside. You would also have to be confident in the adhesive you use will not melt and let the insulation come loose.

Alternatively you can put it in the inside foil side up, it may stop some of the heat reacing the cabine but the floor pan itself will get just as hot.

Locally we often buy "flastac" or home roof flashing from hardware stores to use as a sound deadener. It also has a foil side as well, then bitumen with an adhesive backing. Very easy to use as the adhesive is already there.

[MikeW]

Originally posted by drunkenmaster

Locally we often buy "flastac" or home roof flashing from hardware stores to use as a sound deadener. It also has a foil side as well, then bitumen with an adhesive backing. Very easy to use as the adhesive is already there.

As you can see in the picture I already have a layer of Dynamat installed which is a commercial sound deadener. I think the "thermo shield" layer that I'm going to put on top will be more useful as padding than a heat reflector but should still provide addtional thermal insulation.

[beandip]

don't put that stuff under the car ! I am using b-quiet , Brown bread on my floors and doors . I bought some simular foil backed stuff from Whitneys and its going on the firewall and tranny tunnel as well as the floors . Foil side up. The brown bread has foil on the up side as will. Did you use the dyno mat on the inside of the doors ? If you want to stick the stuff down , you can use some spray adheasive.

[MikeW]

Originally posted by beandip

don't put that stuff under the car !

Don't worry, I wasn't planning on that ...

Did you use the dyno mat on the inside of the doors ? If you want to stick the stuff down , you can use some spray adheasive.

I've only done the driver side floorpan so far but it only took 8 sqaures (12"x12") and I bought 5 boxes of 5. I should therefore have 9 squares left over for the doors and any other place that makes sense.

The Dynamat has an adhesive layer so I'm not sure I understand the spray adhesive part. I do plan on using spray adhesive to hold the other insulation down.

[drunkenmaster]

Well, it is a thermal insulator. I would have used the OEM style rubber backed matting for padding, like in the 300zx etc. Personally after spending so much time removing the factory adhesive matting, I am not keen on glueing anything unnessary down to the car again.

Just to elaborate I attached a photo of the roof flashing I was talking about. For all intents and purposes it appears to be identical to most big names such as some models of dynamat and brown bread.

[MikeW]

Originally posted by drunkenmaster

Personally after spending so much time removing the factory adhesive matting, I am not keen on glueing anything unnessary down to the car again.

Understood. However, after removing the factory tar mat, removing the residue with Xylene, cleaning with Marine Clean, prepping with Metal Ready, and putting down two coats of POR15, I don't plan on ever removing anything from the floorpans again once I'm done with this little project.

How thick is the 300ZX style insulation? I'm worried about building up too many layers and having the carpet not fit properly.

[beandip]

the spray was for the other stuff not the dynomax

[drunkenmaster]

it will definately be thicker than your insulating material you have bought, it is a sheet of rubber bonded to what looks like a mismatch of off cut material, lots of different colours and the overall effect is a purple colour. You will know the one when you see it. Its about 1cm or ~0.5" from memory, so maybe it will cause the probelms you are trying to avoid.

What I ended up doing in my car is using epoxy primer over the sandblasted metal, followed by a sprayed coat of bitumen stone guard topped off with body colour. This way I hope not dirt/water can get trapped between layers and lead to rust and the effect is quite similar to just colour over metal.

In the factory deadening I found this to have happened, where the exposed metal was in top shape but some recessed areas under the deadening where the water can get trapped were signs of rust.

Anyhow, I'm sure you know what you are doing. It took me a long time to make my decision on what to do, that is why I have such an opinion on it. I was also keen to put some heat reflecting material under the transmission tunnel but was worried about the adheisve so never go around to it.