Small front porch with polycarbonate roof

[TonyRPH]

We have a small porch (approx 1.5m x 1.5m) with a sloping polycarbonate roof.

With the warmer days, the heat being generated is quite intolerble, even with both windows open.

Would I have any issues with condensation or similar if I put a sheet of Celotex on the underside of the roof?

I'm hoping this would block sunlight coming through the roof and at the same time prevent heat from getting through the roof, although I appreciate there will still be heat coming from the sunshine through the windows.

Any other suggestions would be appreciated.

Thanks.

A picture of the offending item.

[Equus]

TonyRPH said:

Would I have any issues with condensation or similar if I put a sheet of Celotex on the underside of the roof?

Possibly, yes; the fundamental rule is that you always place the high vapour resistance elements on the warm side of the insulation,; the intention being that you stop the moisture from entering the structure (where it can condense as it cools on the way out) and any moisture that does find its way in stands some chance of escaping though lower vapour resistance elements toward the outer surface.

Polycarbonate sheet is about as high a vapour resistance as it's possible to get, so unless you formed an absolutely perfect vapour barrier on the inside, you're asking for trouble.

Celotex is foil-faced, though, so in theory if you put the foil on the inside, make sure it is undamaged, and carefully tape every joint, then you may be OK. And if the rest of the structure is UPCV (no timber?), the condensation would merely be unsightly, rather than damaging.

[TonyRPH]

Thanks - yes I think I could form a perfect seal.

The roof is essentially a window frame with the polycarb panels inserted like glazing.

I could quite easily cut the Celotext to exactly the size of the frame and then affix it probably using some kind of supports from one side to the other.

This is a more detailed view of the roof if that helps at all.

Edited by TonyRPH on Friday 26th May 17:21

[HarryHill]

You could also change the polycarb for the bronzed version, which will help. Simple job.

[TonyRPH]

HarryHill said:

You could also change the polycarb for the bronzed version, which will help. Simple job.

Interesting that you say that, because our side porch has the bronzed roof, and it is noticeably cooler - although I put that down to it not getting as much sun and being slightly larger.

I guess even a solid colour (if available) would help - we went for white because of it's reflective properties, thinking it would be cooler - but I guess it's letting a lot more light through!

[HarryHill]

Opaque sheets are usually used in vertical as vision screen. May be worth laying a board on top for an hour to see if it will make a difference ?

[TonyRPH]

Good idea.

Congratulations on the 100th post

[TonyRPH]

I actually came up with an idea this morning.

I thought about using something similar to a Velux window blind.

It might need a bit of custom fitment though!