Insulation QUESTION
Safety Car
Joined: Mar 2001
Posts: 4,359
Likes: 116
From: AUSTIN Tx
George,
The bubble product has a R value, but they just are not willing to publish it. Every product in the world has an R value, and the greater the R value, the greater the resistance to heat flow, period. It may just take several inches of one product to equal much less of another product. Insulating properties come from trapped air spaces between the insulating material, and not the material itself. This is why loose fiberglass and foam are such great insulators!
That being said, there are several types of heat, radiant, conduction, and convection.
One of the largest sources of heat gain to the cockpit of the car is through radiant gain. It comes from the heat radiating from the exhaust pipes and mufflers. You can block this heat gain it two different ways, by wrapping the exhaust to keep the heat in, or installing a radiant barrier to reflect the heat away from a surface. Original C2 cars had radiant barriers installed on the pipes under the cockpit, and almost all new cars have some radiant barriers. At the least, most have one over the cat's as they run very hot. Any heat not reflected away by a radiant barrier, will hit the floor of the car and will be turned into conductive and convective heat.
For a radiant barrier to function best, it needs an air space between the hot exhaust and another air gap between the floor of the car. You see a lot of insulation that is intended to go under the carpet. that is foil faced and they try to convince you that the foil is reflecting the heat, but it just ain't so! once you put the foil in direct contact with either the floor and the carpet, almost all of it's radiant barrier properties go away. A foil face on insulation under the car will reflect a lot of radiant heat, and this is how the trans tunnels were originally insulated. A shiny foil surface turned to the inside and covered with foil, is just about useless.
Insulation is very effective against conducted gain and convective gain. Once again, R value is king, the larger the R value, the less heat gain. There is so much Snake Oil being sold out there that it is very hard to figure out what is really effective. Most manufacturers do not publish R or U value numbers for their product, and they do so for a good reason, If the did, you could see just how pathetic the performance of most of them were!
Your best bang for the buck it to stop as much of the heat as possible from hitting the floor of you car through radiant barriers, and then use the highest R value insulation you can find for the floor and firewall.
I usually use either Dynaliner or Armaflex commercial insulation. The only downside of using rubber foam insulations like this, is that they can affect the fit of carpets if you are not careful. I usually use either 3/8" or 1/2" insulation to maximize the R value, but you have to trim and taper the edges very carefully to make the carpet fit well. Neither of these insulations are applicable for a NCRS car, as the judges would spot them in a minute. On C2 cars, I also insulate under the console plate as well. You have to look at every avenue you can to try an block heat, but if you take a systematic approach to insulating a car, you can make some real gains.
Nothing can take away the enjoyment of driving an old Corvette like roasting in the cockpit while sitting at stop lights!
Regards, John McGraw
The bubble product has a R value, but they just are not willing to publish it. Every product in the world has an R value, and the greater the R value, the greater the resistance to heat flow, period. It may just take several inches of one product to equal much less of another product. Insulating properties come from trapped air spaces between the insulating material, and not the material itself. This is why loose fiberglass and foam are such great insulators!
That being said, there are several types of heat, radiant, conduction, and convection.
One of the largest sources of heat gain to the cockpit of the car is through radiant gain. It comes from the heat radiating from the exhaust pipes and mufflers. You can block this heat gain it two different ways, by wrapping the exhaust to keep the heat in, or installing a radiant barrier to reflect the heat away from a surface. Original C2 cars had radiant barriers installed on the pipes under the cockpit, and almost all new cars have some radiant barriers. At the least, most have one over the cat's as they run very hot. Any heat not reflected away by a radiant barrier, will hit the floor of the car and will be turned into conductive and convective heat.
For a radiant barrier to function best, it needs an air space between the hot exhaust and another air gap between the floor of the car. You see a lot of insulation that is intended to go under the carpet. that is foil faced and they try to convince you that the foil is reflecting the heat, but it just ain't so! once you put the foil in direct contact with either the floor and the carpet, almost all of it's radiant barrier properties go away. A foil face on insulation under the car will reflect a lot of radiant heat, and this is how the trans tunnels were originally insulated. A shiny foil surface turned to the inside and covered with foil, is just about useless.
Insulation is very effective against conducted gain and convective gain. Once again, R value is king, the larger the R value, the less heat gain. There is so much Snake Oil being sold out there that it is very hard to figure out what is really effective. Most manufacturers do not publish R or U value numbers for their product, and they do so for a good reason, If the did, you could see just how pathetic the performance of most of them were!
Your best bang for the buck it to stop as much of the heat as possible from hitting the floor of you car through radiant barriers, and then use the highest R value insulation you can find for the floor and firewall.
I usually use either Dynaliner or Armaflex commercial insulation. The only downside of using rubber foam insulations like this, is that they can affect the fit of carpets if you are not careful. I usually use either 3/8" or 1/2" insulation to maximize the R value, but you have to trim and taper the edges very carefully to make the carpet fit well. Neither of these insulations are applicable for a NCRS car, as the judges would spot them in a minute. On C2 cars, I also insulate under the console plate as well. You have to look at every avenue you can to try an block heat, but if you take a systematic approach to insulating a car, you can make some real gains.
Nothing can take away the enjoyment of driving an old Corvette like roasting in the cockpit while sitting at stop lights!
Regards, John McGraw
Last edited by John McGraw; Jan 5, 2009 at 02:10 PM.
