best thermal insulation floor carpet of corolla: fiberglass batt or closed cell foam between double sided aluminum foil

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Good afternoon.


I have a fiberglass batt with a thickness of 17 mm and according to the internet 1 inch=25.4 mm of the fiberglass batt has an r value of 3.5. I also have available to me a closed cell polyethylene foam sandwiched between double sided aluminum foil thermal insulation with a thickness of 3 mm which according to the manufacturer when the thermal insulation finds itself in a system with a space of 1 inch of air has an r value of 12. I sent an email to the double sided aluminum foil manufacturer to ask what r value only the material has as they don't dislose that info on the technical specifications sheet. The double sided aluminum foil available to me resembles this: https://www.amazon.com/US-Energy-Products-Reflective-Insulation/dp/B07QX5LGBX I wonder what kind of r value this double sided aluminum foil has by itself and if an inch of this aluminum foil type insulation has an higher value than an inch of fiberglass batts.

Perhaps a better budget insulation option : aluminum foil paper on the floorpan and then the fiberglass bat?

thanks
 
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The foil facing is being a little sneaky with their R-value claim and it has been the bane of people within the building community.

R-value is an expression of the resistance of heat moving through a material.

Foil facing companies make their exaggerate claim because the air space allows for reflectivity of radiant heat which they lump in with the R-value of the foil/foam sheet. The key is the air space and companies have been sued for false advertising because they would omit the 1-inch air space in their advertising. The R-value of the sheeting itself is around 1.


I have to ask why are you considering using fiberglass insulation under the carpet of your vehicle and why do you think it'll work?
 
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I don't have an answer for you, but I'm curious as to why you're insulating the floor of your corolla?
 
The foil facing is being a little sneaky with their R-value claim and it has been the bane of people within the building community.

R-value is an expression of the resistance of heat moving through a material.

Foil facing companies make their exaggerate claim because the air space allows for reflectivity of radiant heat which they lump in with the R-value of the foil/foam sheet. The key is the air space and companies have been sued for false advertising because they would omit the 1-inch air space in their advertising. The R-value of the sheeting itself is around 1.


I have to ask why are you considering using fiberglass insulation under the carpet of your vehicle and why do you think it'll work?
to lower the cabin temperature for more efficient cooling with air conditioning like this:

and also for acustic insulation.
 
to lower the cabin temperature for more efficient cooling with air conditioning like this:

and also for acustic insulation.

If the concern is AC, I think I would look at tinting the windows (check with local laws on how much is allowable; varies by state).

Also consider "screens" that block sunlight. My SIL uses the fitted screens on the side/rear/front windows his Altima and he said it's amazingly cool even after sitting in the sun all day. His job is such that he can eat in the car at lunch, and even take a short snooze. I think he uses Weathertech but am not sure. They are specific to each window and may just attach with velcro.

I seriously doubt insulating the floor would help. Remember that cold settles, while heat rises.

And make sure the AC is functioning like it should ;o)

EDIT: I guess it always helps to watch the attached video ;o) I had not realized the heat coming through the floorpan like that. One caveat: a Corolla is front drive vs a large V8 in that wagon. Point is, while it can make a big difference like in the video, it may not in a Corolla. It would seem to matter if the heat you speak of is coming through the floor or from direct sun through the windows. I assumed the windows and still think it the most likely source.

Off topic, I've wondered about using insulation padding (foil with heavy media, like in the photo you provided) on the ceiling of a car. The silencing could be quite noticeable, and there would be some thermal benefits. Problem is removing/replacing the headliner is a real PITA on most cars.

HTH
 
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How long do you think this idea would last?

The other concern is fiberglass fibers floating around inside the car and thus you breathe them in.

This cannot be a serious idea.
 
I'd just go the car sound insulation way with CLD on first then CCF foam on top. It works pretty well and as a bonus, helps sound reproduction. I also noticed, in the focus, it kept it either colder or hotter compared to the outside temp, to help your cause.

But did you already tint the windows at least?

The other concern is fiberglass fibers floating around inside the car and thus you breathe them in.

I would think so too, but I have no knowledge of insulation.
 
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Sounds like radiant barrier … you have to keep at least one surface clean to function as that - double sided/sandwiched does
 
How long do you think this idea would last?

The other concern is fiberglass fibers floating around inside the car and thus you breathe them in.

This cannot be a serious idea.
I googled fiberglass batt and I didnt find a picture of anything that looks like the insulation I have. It looks blue with fibers of different colors; it actually looks like a recycled denim fabric batt which has basically similar thermal and acoustic insulation as fiberglass sans the toxicity.

I will also do the headliner with same materials as the floorpan with recycled denim fabric batt and aluminum foil window shades. Probably layer up double on the aluminum foil window shades on the roof as it gets hotter than the floorpan.

I have pretty dark non reflective black tints on though I guess some 3m quantum mirror reflective tint would provide better cooling perhaps.
 
If you want to keep out the heat, insulate your exhaust system with thermal wrap. The exhaust system is the single largest heat emitter under the car.

Start at the exhaust manifolds and go back.

No point in doing the interior is you can do it on the outside and keep the heat from getting onto the floorboards to begin with.
 
to lower the cabin temperature for more efficient cooling with air conditioning like this:

and also for acustic insulation.

Radiant barriers reflect heat back into the air space. It no longer functions as such for the foil face which is in contact with other materials. Once the material is sandwiched between two other materials the amount of heat transfer is based on the foil and the thickness/type of insulation between the two-layers of foil. What the guys in your video should've done is attach the foil to engine side of the firewall and underside of the transmission tunnel. Could've done it with a whole lot less material.

There's automotive insulation which you can buy that will reduce some noise however there will be areas which you cannot reach such as the inside of the A-pillar and design constraints (ie. side mirrors) so it won't be perfect. Fiberglass insulation would never work and it's the incorrect material for the application.
 
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The biggest heat load comes from the windows having a green house effect on the inside. That insulation will do nothing except add a weight. Also, for insulation to be effective, it needs to be air tight and cover close to 100% of the external walls. A car is not a house and cannot be insulated as one.
 
year/make/model/issues and location might help get better responses. Why on every auto forum is 'info' left out for the psychics only.

I also vote for a good sound deadener application. It provides some insulation too.
Some mats and CCF:

Regardless of what you use, unless you cover the firewall, doors, headliner/ceiling, and address what your issue is(cold/hot)... and have the A/C serviced if heat is an issue.

Quality ceramic/nano fancy tint will also block heat. Doesn't need to be dark. Dark(dye/metallic) tint does not block heat. So, learn your state laws and find a tint shop with IR lamps so that you can compare tints. Most of the cheap dye/metallic tint will turn your car into an oven. Needs to be IR blocking. Even the overly clear 3m "90" does wonders when the windshield is illegally tinted with it and is really not noticeable. Sticker shields/ezoff... are available for parking/trash/park/beach/HOA permits and vehicle state inspection permits too.
https://www.3m.com/3M/en_US/p/d/b00016683/

Live in a hot climate now and avoid darker cars.... white, pearl white, and maybe silver are my only new car color choices... all those black, dark blue/reds/browns are ovens down here. Same clowns with black painted cars complain about A/C performance too. Get car wrapped in white vinyl.

And, don't forget the good ol' classic rubberized/asphalt rust proofing. Spraying the undercarriage with it will provide some noise and heat insulation besides the weather protection.

And park with a sunscreen:

Use visors and leave windows 1/4" open on sunny days:

My favorite pet peeve... went to Toyota dealer to look at new Camry. They had one in white... problem is... &^%$&(* automaker does some *&^% two-tone black roof BS. Why the hades would I want a white car with black roof when its sunny and 105F outside? Did they not notice all the orange/yellow school buses with white painted roofs, or those toasty brownie delivery trucks with white roofs? Toyota needs to fire their rocket scientist paint color marketing clowns.
 
In practical applications, closed cell foam always outperforms any insulation that has internal airflow.

This is why camping in cold weather often requires a closed cell foam pad between the sleeping bag and the ground. Not only does it maintain it's insulation distance of about 1/2 inch under compression, but it does not have any airflow when a sleeping person moves around.

Same goes for cars, closed cell foam will be more effective, thermally, thickness for thickness. However, a nomex insulating blanket, topped with a closed cell foam layer, will reduce noise considerably more.
 
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