Straight from the SecondSkin website:
"The thick foil on Damplifier offers three thermal insulation benefits.
First, the foil acts as a radiant barrier, reflecting heat back towards the source. When used on the firewall, this prevents as much heat from making it in to the cabin of the car. Less heat means cooler temperatures.
Second, the foil heat shield on Damplifier is dissipates heat by increasing the surface content, allowing for thermal dissipation and reduction.
Third, the butyl layer slows down any remaining heat from getting in to the cabin of the car. The longer it takes the heat to get to you, the more comfortable you are."