Insulating Polycarbonate Roof

[Onoff]

Mate has a twin wall polycarbonate roof on his conservatory / lean to. Old terraced place he's just moved into. Double glazed windows and half walls on the lean to.

 

In the Summer he reckons it can get to 40deg in there.

 

He's voiced a plan to me to "insulate" the roof at the same time blocking out the light.

 

He's got 60mm from the underside of the roof beams to underside of the polycarbonate.

 

He's proposing fitting 50mm pir between the roof beams. Foil space blanket up on the ceiling followed by upvc cladding to keep the weight down.

 

I mentioned that looking through the polycarb from the outside you'll see the silver pir.  He's mulling over then painting the outside of the polycarb.

 

Will this work, is it practical? I'm wondering whether there'll be any condensation issues between the top of the pir and underside of the polycarb.