There is not much unbiased data out there to give you on this but some manufacturers have done real world tests comparing foil with standard insulation with encouraging results.
Thin foil insulation blanket.
This reflective insulation product is not only versatile but very easy to work with and install.
Often used to create curtains and screens this fabric has an aluminum foil backing that deflects radiant heat.
A space blanket also known as a mylar blanket emergency blanket first aid blanket safety blanket thermal blanket weather blanket heat sheet or shock blanket is an especially low weight low bulk blanket made of heat reflective thin plastic sheeting.
It means that foil insulation is going to have a higher u value but may well perform better than expected in the real world.
Ffbib is a true vapour barrier which may be necessary for conditioned spaces.
Building insulation blanket bib and foil faced bib ffbib roofing building insulation blanket bib and foil faced bib ffbib are designed for use under any roof system which requires control of temperature loss or gain.
A space blanket forms a barrier between the wearer and the wind providing insulation.
Lastly we also lose body heat through radiation it simply radiates off our body.
Staples screws washers foil tape contact cement or construction adhesive.
The reflective agent on space blankets usually silver or gold reflects about 80 percent of our body heat back to us.
Multiple options are available for fastening the product.