Guidance needed.

Maclock

Hi all.
Could someone please guide me in the right direction.
I have a new 20' X 10' steel shed that i want to insulate.
I've spent lots of time looking through different posts and reading various articles but all they've done is make me more confused.
I'd like to use the shed as a workshop and also maybe to put in some fitness equipment.
I'll put on a stud wall whenever I get around to it.

I've almost sealed every bit of the shed with expanding foam and silicone as to stop any draughts.

The insulation I have is, 12.5 plasterboard with 50mm of pir.
I also have 25mm foil backed kingspan.
This might seem like overkill for a shed but i want to do a proper longterm job.

What I'd like to know is, does there have to be an air gap behind the insulation and basically how I should go about fitting it?
Any advice would be greatly appreciated.

sky6

You would probably be better just getting the inside of it spray foamed. Any gap left behind insulation may cause problems with changing temperatures.

whizbang

Put in as much effort as you possibly can, air sealing the inside from the outside (of the insulation). This means no moisture can get past onto the cold surface of the metal.

There will of course be a small amount already there, so ideally just a tiny gap, to allow some small airflow.

Maclock

sky6 wrote: »

You would probably be better just getting the inside of it spray foamed. Any gap left behind insulation may cause problems with changing temperatures.

I unfortunately don't have the money to spend on getting it spray foamed. I thought that the insulation I already have would do the job if fitted correctly.

Maclock

whizbang wrote: »

Put in as much effort as you possibly can, air sealing the inside from the outside (of the insulation). This means no moisture can get past onto the cold surface of the metal.

There will of course be a small amount already there, so ideally just a tiny gap, to allow some small airflow.

The steel is 40 mm box section so my plan was to fit 3X2 pieces of timber in between at
200 mm centres, then fit the full sheets of 25mm kingspan horizontally across, tape the joints with aluminium tape, then fit the plasterboard sheets vertically.
I would have thought the Kingspan would stop the moisture getting through but there would already be 40mm - 50mm of a gap behind.
That size air gap is only asking for trouble, is it?

whizbang

No Issue with air gaps. Just as a trickle of airflow around inside the gap. Front to back, bottom to top, whatever.

The insulation is more or less moisture proof, so sealing the joints is all thats needed.