Steel Shed Insulation Questions

gary550

I recently got a steel shed put up which will eventually be used as an office. The shed itself is uninsulated (just the non drip lining) and it has a PVC door and window, on a concrete base which is damp proofed.

I was going to buy it insulated from the supplier but it was a fair bit extra and the finish was not that great in my opinion. I looked into spray insulation but the only quote I got that was reasonable was from a lad doing it as a cash job and I don`t want to go with it in case he does a terrible job and I`ve no recourse. I looked for quotes from a good few places and half of them didnt even get back to me and the other half added an extra 10-15m2 on the quote and were looking a fairly hefty rate. (plus I hate the look of it)

So I think I`m back to the original plan of insulating it myself. The plan was to add additional lengths of timber to affix the plaster-board to, then insulate it in between with PIR 30mm boards, fill up any gaps with expanding foam and tape up with aluminium tape, then plasterboard it. Is there any need to leave an air gap or add a vapour barrier? Is there any chance of damp passing through the insulation and condensing of the cold steel behind it leaving damp?

Any help or advice would very much be appreciated! Thanks.

listermint

Needs a vapour barrier and taped at the seems.

How are you venting it. Making an airtight room and putting a living breathing person inside it will create humidity .

Calahonda52

Hope big is the shed?

gary550

listermint wrote: »

Needs a vapour barrier and taped at the seems.

How are you venting it. Making an airtight room and putting a living breathing person inside it will create humidity .

Ah OK thanks, I`ll add a vapour barrier to the list then so. In order of placement would I be right in saying that should that go on the underneath of the plasterboard and on top of the insulation?

Never really put much thought into ventilation, there is a window with a fairly wide opening which I imagine will be opened when I`m in the shed. I`m working from the house at the minute and usually have the window opened most days even in the winter.

As far as ventilation should I be putting something a more permanent in? I never noticed dedicated venting on any of the display sheds I seen with any of the manufacturers but then again I wasn't really looking for it.

gary550

Calahonda52 wrote: »

Hope big is the shed?

Only 3 x 3m which is 10 x 10 foot. Had space constraints or I would of went much bigger. None the less its ideal for what I need at the minute.

JimmyMW

In a similar situation, want to insulate a steel shed, had initally considered a stone wool type insulation against the metal cladding with a vapor barrier behind it and then plyline it, however i am conscious of condensation between the metal cladding and the insulation as there will be essentially no ventilated cavity. Spray foam came up as a good alternative with a similar build-up. Any thoughts on the best way to go in this instance?

whizbang

Because theres no way for moisture to escape through the metal wall, the complete installation has to be be vapour proof.
But I still would look to create some small amount of ventilation behind the insulation. A lot of sheds would have air gaps under the roof ridge, then just add a few small holes around the bottom of door, window frame etc.

Ventilation in living space is still required, Theres a great article somewhere about creating a convection flow system behind the insulation, powered by the sun heating the outside panels.

Re membranes; foil backed PIR is as vapourproof as it gets.