workshop insulation

Sorry in advance if is in the wrong section, but I wasn't sure where else to put it.

I'm in the process of extending my workshop into and adjoining garage. I will need to insulate the skillion corrugated roofed of the new area, due to it westly aspect and low roof height.
Roof beams are 140 x 50 hardwood, 900 mm spacing with a 2 mtr span.

Ideally id use 75mm XPS (Extruded Polystyrene) foam sheets, for there excellent thermal properties and easy of fitting. which would allow a good air gap to help with condensation.

As a retiree this is a bit much for my budget,
I've found some secondhand "cool room" panels ( polystyrene foam with aluminum sheet)glued to each face ) for cheap and wonder if I can use these instead.

Interested to hear ppls thoughts and suggestions

I think they'd be an excellent substitute.

I used thermal blanket (essentially insulation batt with one reflective side) over the battens, directly under the steel roof. Works well. Light and easy to install before the roof goes on.

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Originally Posted by Oldhack

Sorry in advance if is in the wrong section, but I wasn't sure where else to put it.

I'm in the process of extending my workshop into and adjoining garage. I will need to insulate the skillion corrugated roofed of the new area, due to it westly aspect and low roof height.
Roof beams are 140 x 50 hardwood, 900 mm spacing with a 2 mtr span.

Ideally id use 75mm XPS (Extruded Polystyrene) foam sheets, for there excellent thermal properties and easy of fitting. which would allow a good air gap to help with condensation.

As a retiree this is a bit much for my budget,
I've found some secondhand "cool room" panels ( polystyrene foam with aluminum sheet)glued to each face ) for cheap and wonder if I can use these instead.

Interested to hear ppls thoughts and suggestions

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I am almost sure the panels you have found cheap will be colorbond steel not aluminium meaning they will be considerably heavier than just polystyrene on it's own, so providing you are up to installing them with help from someone, then by all means use them.
You don't say how thick the panels are so assuming they are 50mm you can use a couple of methods to fix them.
(1) One method assuming you have 40mm timber roof battens would be to use hex roof screws/batten screws or similar through the panel into the battens.
(2) Another method would be to use flat steel say 150x40x6 with one 25x12 hex roof screw in the middle of said steel into the beam each side to hold one edge of 2 panels.
My preference would be (1) providing the battens are not too dried out so they won't split.
Of course I believe nothing is better than wool and siso (anticon blanket) but the roof would have to come off for that.
That is what I used in my garage when I decided it was too hot for a beer garden.

Problem you may face with the panels may be condensation dripping onto the panels and running down the insulated sheet then dripping into the workshop area.
I don't know having never used them in the situation you have.

To the best of my knowledge there should be little or no condensation with insulation panels under the roof due to the insulating factor, but I have never removed a roof sheet early morning in winter when condensation should be heaviest.

Thanks for the replies.
As I have a lots of used aluminium angle, I'm going to run it around the perimeter of the area to be insulated, the panels will sit on this and then I'll fix the panels to the angle with wafer screws