To better isolate, I think !
To ensure its sustainability, the two sheets reflecting the constituents of the envelope of the insulation are pure aluminum.
Limit the use of expensive air conditioning.
To increase the summer comfort, the aluminum acts as a mirror, reflecting the heat transmitted in the form of infrared light.
A polyethylene film protects the aluminum from any risk of blows or tears.
To ensure the insulating capacity during very long years, of myriads of air bubbles watertight encapsulate a foam soundproofing closed cell.