I bought new door insulation pads that get glued to the plastic door panels. The new ones have a foil backing. Do I face the foil in (towards the plastic panel and truck interior) or out? They call it a vapor barrier, but with all the holes, I can't imagine it's doing much.

Thanks!

 

Probably wouldn't matter either way. Do yourself a favor and buy some sound deadener. Dynomat or Killmat. Cover all the door holes with the sheets except for where the plastic door panel clips to the door. Your stereo will sound much better and it significantly cuts down on road noise. The cheap insulation stuff doesn't do much of anything. Dynomat is expensive, the Killmat is much cheaper and does almost the same as the dynomat IMO.

 

Amazon has a nice product and it is sticky as sticky can get.

 

FWIW foil goes in, toward the cabin

 

Thanks, KingDeleted! Last night, I read on a hotrod forum that the foil will scratch the metal panel and lead to more rust - so your advice makes sense. I'll face it towards the cabin.

 

Thanks everyone. I put butyl deadener on the outer panel. Between the new weatherstripping and the deadener, the door sounds like a vault when you close it! I have some of the foam material you recommended, 77&79F250, but it might be too thick. I had considered putting that on top of the butyl mat, but now I'm wondering if the inner panel would make more sense - covering the holes at the same time - as Deadbuck suggested. I have this material left over from when I insulated the floor and firewall.

 

If you can find factory original clips they have a small foam pad that seals the door holes.

 

So if it can scratch the inner metal panel, what do you think it will do to your door glass if the glue gives way and the stuff falls towards the glass? Yes I know devils advocate.

FYI I would NOT seal the bottom of the door drain slits.

 

You are gonna put it between the plastic door panel and the inner door steel I hope, so then foil would go against the plastic door panel. I would not in any way, block door drains or glue material inside the doo against the outermost door skin metal. You'll never keep water or moisture out of the door interior but anything glued in there will just trap moisture against steel, often unpainted steel even.

Moisture barrier is intended to protect surfaces from moisture in heated air condensing in contact with cold surfaces. What we think is a moisture barrier behind the plastic of these old trucks is mostly there to prevent drafts. You'll never keep moisture or water out of those doors. Anti-rattle strips do not stop rain or wash water.

Why many vehicles just have a sheet of plastic or a type of cardboard stuff there, often only as a "draft barrier".

 

Well, darn! So maybe I should pull the deadener off the outer skin and put some on the interior side of the inner skin instead. But the massive holes in the inner skin will let a lot of sound in unless I seal them.

What you say about moisture getting trapped makes sense, but the same would be true for most dynamat applications like the floor, rear cab wall, hood, and ceiling.

The drains at the bottom of the doors are definitely staying open!

 

I don't use the dynamat for those reasons you cite. Those holes in the inner panel are needed for servicing. It's an old truck, it's no noisier now than it was when first bought. For sure, it's a little louder than my '07 inside, but the '07 does not have anything glued to the outer skins either, rather it has material between the exposed inner interior door panels and the inner door metal. The last layer before the inner door panel is a moisture barrier, like in the walls of many homes ..... and for the same reason. Moisture barrier is not there to fight rain off. It is there to stop moisture from living room air being trapped in the wall in the insulation itself and any wood in contact. People breath, they exhale moist air, warm heated air hitting cold surfaces condense moist lived in warmed air into water drops.

I've had other cars and trucks with AC that on a hot summer day, would build a frost cover area on the side glass near an air outlet from the AC that got the glass so cold that frost built up. Frost was from warm moist breathed air in the cabin hitting that cold glass, even on a 100 degree day. Those vehicles had Frigidaire AC systems. The "worst" of them was a '70 Chevrolet CST-10 or my '67 Chevelle, those things could get cold.

I made my inner door panels of largely wood to have easier access those several holes (and to look different) ... but it's sealed dried wood, and it is also covered on both sides with a vinyl to protect the same wood from water / moisture. My speakers have water proof foam like back shields. Inside my doors is paint, and at the bottom is seam sealer under the paint .... and some brushed in Iron Armor bed liner over the paint, and the drains are open. I don't need moisture barrier except to prevent moisture being absorbed by a porous insulation. Wood is a porous absorber .... as well as a building material. It can, depending on density, transmit impact sounds. I live in a log home, it's quiet, it's warm, it has no added insulation to absorb moisture. It has polyurethane inside, and a treatment outside. My ceilings use 3-1/2" styrofoam sandwiched between the interior wood and outside wood bonded surfaces, then black tar paper, shingles, white underlayment, and finally a steel roof. I can hear a bird or squirrel on the house, but barely hear the UPS driver in the drtiveway or trucks on the interstate climbing the grade 150 yards away. That row of pines helps.

That dynamat has a foil side .... right? It only works to protect the dynamat insulation from moist air that may condense in the insulation if the foil faces the warm moist air. I would not have it inside my doors .... but I know many use it.

I can imagine it now .... glue comes loose ... mat falls into glass or other mechanisms ... rain water or wash water comes in down past the glass anti rattle strips .... I find a mess in there.

If the goal is a quiet cab ... carpet it all over the inside.

 

Have a look at Second Skin Audio website, they have good info on how to properly sound deaden a vehicle. There stuff is not cheap but I think it's quality. A lot of these foil companies will tell you to cover everything but you only need about 50% coverage to deaden a panel, then you put the mass loaded vinyl over that to make it quiet. Before I knew this I did my cab with foil everywhere, I think it made road noise louder because there was no sound absorption. I've now put the MLV over the floor and the second skin foam stuff on the roof, just waiting to do a road test to see how it worked.

 

I'm still not convinced water would get under the mats and lead to rust. I've gone down the rabbit hole today, and it seems there are arguments both ways online. But I haven't seen a single post where a person attributed panel rust to dynamat. Sealing the drain holes is a different matter. The butyl should seal pretty well, assuming you use a roller, especially around the top and perimeter. My '78 has rust in lots of areas - but not the interior of my doors. It seems more likely I'll encounter rust issues with the frame, fasteners, wheel wells, etc. before I have a door panel rust out. I put butyl sheets in my 2009 toyota about 7 years ago and haven't had issues. And the toyota is parked outside.

Am I trying to avoid removing what I've already installed?: Yes
Could I be wrong?: Yes
Have I been wrong before?: Eh

 

Rust....





Yes this guy might eventually have some rust issues around his headliner area and A pillars. Probably his B pillars too. Moisture intrusion is a hard battle.

 

Sweet convertible!