Does fiberglass insulation lose its effectiveness from compression?
Question:I am thinking about insulating the hood of my car with fiberglass insulation sheets -- yes the same kind that most people use in their walls. To make it fit in the engine bay, I will need to compress it, and keep it in a compressed state. I have no worries about overheating, as I will have MANY gauges to check temps with.
I am just concerned with the effectiveness of fiberglass insulation, in its compressed state. Any R-value changes would be really appreciated!
Answers:
If you compress fibreglas insulation, it loses its effectiveness, because it depends upon the air trapped in the spaces among the fibers. I would estimate that if you compress it to half its thickness, it would lose half its insulating power, at least. For the person who stated that fibreglas insulation is unsafe to be around, this is untrue. It is asbestos that is unsafe to be around. The only "danger" from fibreglas insulation is if you handle it without wearing protective clothing, especially gloves - the thin fibers of glass will irritate the skin. Fibreglas will not burn; it is not a fire danger. Styrofoam insulation would be dangerous to use in a situation involving high heat as it gives off a poisonous gas if subjected to flame.
Id be surprised if you could still buy figerglass. It is not safe to be around, I havent even thought of the heating it up aspect.
Call your dealer, find out what he wants to use, then go to Pep Boys and see what they have that will cost a whole lot less.
You have to install it loosely. It loses it's R-Value if you compress it. The trapped air between the fibers is what gives it good R-value..
...oh crap, I didn't read the entire question. for you car? are you nuts? It will catch fire! lol No way dude. I thought you meant for a house.
Uhh . . . Yes compression will destroy it's ability to hold warmth. It's the air spaces that hold the heat. But it will burn up and cause a engine fire you wacko! Wrong product! Wrong use!
Regardless as to what I think about your application, the answer is, YES, it will lose its effectiveness from compression. For instance, insulation with an R-11 value is 3 1/2" thick, to fit in a wall cavity with 2x4 construction. In this application, if you want a greater R-value, you would use an R-13, also 3 1/2" thick. You would not put an R-19 (designed for use with 2x6's, so it is 5 1/2" thick) into that 2x4 space and compress it, it is the open air space in the insulation that makes it effective.
Fiberglass does lose it's R-value when compressed. I disagree though, with those who say it is flammable, but only because it isn't. Of course if there were paper backing on the fiberglass, that would burn.
that's ridiculous Ive worked with fiberglass insulation for many years and a lot of times you have to compress it it will the exact same way there will be no difference, why would you want to insulate your hood anyway?
Bad idea. Compression kills it.
They're right, if compressed it will lose it's insulating value.
However, the original headliner was made from compressed fiberglass insulation with some type of upholstery glued to it. I can tell you this for a fact because I use to make such headliners at a factory that specialized in acoustical sound deadening parts for cars. We put a 6" sheet of fiberglass insulation treated with a polymer resin into a press with a heated mold. It came out of the press 1/8" thick and in the shape required for that make and model of vehicle.
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