When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I am in the middle of replacing the carpet in my 78. I've searched the threads but haven't found an answer to a puzzle i'm trying to solve. I already put dynamat extreme and reflectix down. Now I have a pre cut carpet underlayment (front only) set that I purchased from CA. It came with 4 pieces. 2 clearly are for the front floor area. But there are 2 additional pieces. One cut out with a stair like pattern and thick insulation. The other rectangle with dense insulation between 2 foil sheets. Where do these other 2 pieces go? My underlayment didn't have instructions and I haven't been able to find anything about them. Any info would be extremely helpful.
I've also read on this forum and from Willcox that the underlayment is supposed to be installed with the foil side down. The pre cut pieces don't seem to fit this way. They only appear to be cut to fit with the foil side up. Is it acceptable to install it that way considering I have the dynamat and reflectix already down below? Or should I return this product for something different?
Thanks.
Stock photo below. I should have taken pics before I left town this morning. But this does show the stair cut piece with the thick yellow insulation. And below it is the double foil sided rectangle. I can submit regular pics when I’m back in the garage Tuesday.
Last edited by Bingo844u2; Mar 6, 2020 at 03:59 PM.
Reason: Stock photo added
With regards to the "foil side up vs. foil side down" question it's hard to say if the foil even matters in such an application let alone which way is better. That said since you have reflectix at a lower level there is utterly no difference.
Don't forget that soft factory insulation materials are there for sound reduction--not temperature control!
If you want to maintain a temperature inside a space where the exterior temperature varies greatly the best--BY FAR--place for the insulation is exterior to the space with controlled temperature! This is why durable radiant--typically aluminum--heat shields are installed between very high temperature things like exhaust pipes and the cabin.
On ANY insulation product, the foil side faces the source of the heat. Foil is meant to reflect radiant heat (one portion of the heat components). It is BEST to reflect radiant heat FIRST, then let the rest of the heat 'fight' its way through the fiberglass mat.
On ANY insulation product, the foil side faces the source of the heat. Foil is meant to reflect radiant heat (one portion of the heat components). It is BEST to reflect radiant heat FIRST, then let the rest of the heat 'fight' its way through the fiberglass mat.
You're correct but as this applies to the underneath of a car the foil should be exterior to the floor pan which for obvious reasons is utterly impractical. That's why the only truly hot things (exhaust pipes) under there have rigid heat shields (radiant barriers) installed just above them. Those shields stay reasonably reflective and effective because they are themselves mostly shielded from dirt, oil, etc with the side facing the exhaust getting hot enough to essentially burn off most things like in a self-cleaning oven. Provided that effective heat shielding is used the interior surface temperature of the floor pan in most places won't be particularly high and the effectiveness of a radiant barrier in a multi-layered system (floor pan, carpet backing/insulation, carpet) becomes negligible compared to the radiant heat being delivered from the inside surface of the windshield and other windows. BTW, while visible light passes through glass, infrared "light" e.g. "heat" does not. A sunny south [single pane] window on a frigid day doesn't emit heat because the energy from the sun is passing through--it does so because the sun has very efficiently heated the thin glass.
Thanks Interpon for the pictures. After manipulating the Underlayment, it does seem to fit with the foil side down. However, like you have it installed, it seems to fit more naturally with the foil side up.
Foil will reflect radiant heat, wherever it is installed. The fact that the foil faces the floor is BENEFICIAL; the heat is re-directed OUT of the passenger compartment.
Last edited by 7T1vette; Mar 12, 2020 at 09:51 PM.
Thanks Interpon for the pictures. After manipulating the Underlayment, it does seem to fit with the foil side down. However, like you have it installed, it seems to fit more naturally with the foil side up.
i am 99 percent sure the carpet i took out was original..even the painted rivets and backing from factory tape sealing the vents..i noted the sloppiness when i removed..also where the cat burned the floor was like peeling tape
Matched to backing of factory foam in the heating ducys..ripped out from leaking heater core
Last edited by interpon; Mar 13, 2020 at 07:24 AM.
Thanks Interpon for the pictures. After manipulating the Underlayment, it does seem to fit with the foil side down. However, like you have it installed, it seems to fit more naturally with the foil side up.
forgot to say..i had rattle as well where cat is..now is a great time to add some heat and sound insulation..dont need to cover it all just certain areas..dont put behind pedals...really quieted down.. Amazon..not too pricey..worked great only used on passenger side as i was redoing heater core
Carpet underlayment puzzle
