Insulation ?

[pipes]

http://www.insulation4less.com/

I just bought a roll of insulation for the bus, from the above link..........They recomend having an airspace of at least 3/4".
My ? is, I have large amount of ceiling tile about 1.1/2" thick fiberglass, aluminum foil one side fabric on the other side. If I stuff this AND the 1/4 " new insulation into the bus frame (sides above deck) can I consider the FIBERGLASS as air space???...........TIA Ken.

[brojcol]

It's not the same thing.  The foil insulation works because of its reflectivity.  It needs to be able to reflect the heat "somewhere" hence the airspace.  I would be particular about not following the manufacturers instructions implicitly in using this stuff.