Insulation for a wooden shed

[mock]

Any videos tip or suggestions on insulating my wooden workshop that should be complete by mid January ? should i also insulate the floor ? I have been thinking of using Celotex boards or similar around the walls and flat roof between the rafters ' should there be a gap between the insulation boards and the roof ? thanks' in anticipation Mock

 

[robgul]

I insulated a timber shed using Celotex, cut to fit snugly between all the frame battens and then clad it with OSB - did the roof too (no gap) in the same way - no issues. I didn't insulate the floor as it wasn't in direct contact with the groud - the shed was on a frame/platform made with 6 x 2 treated timber (obviously 6" high) that were placed on paving slabs of the whole shed base area.

 

[Doug B]

I insulated my last shed with celotex type insulation 25mm thick on he floor covered with 8x2’ t&g MR chipboard flooring left floating but glued the tongue & grooves certainly felt nicer under foot.
The walls & roof were done with 50mm Insulation & gaps filled with spray foam, the walls were then covered with melamine faced chipboard the cover sheets that come with packs of boards which I picked up foc from my local timber merchant.

 

[spb]

This thread is what you need to be reading first. Read the whole thing, really, but the key points to take away first are: OSB goes on the inside, not the outside, of the wall insulation, and you need a ventilated gap outside your insulation on both roof and walls.

Insulating the floor is down to preference. You're unlikely to be in the workshop without wearing outdoor shoes, so I probably wouldn't bother, but it's up to you.

 

[Fitzroy]

Mike's thread is great and if you can follow it to the letter you should, you will end up with a building that will last you a lifetime. If you can't follow it precisely it's worth understanding what the issue is you are trying to solve and the problems your compromises could result in.

When you install insulation you create a warm side and a cold side. When you work/live on the warm side any moisture you produce (through perspiration or respiration) will increase the relative humidity of the air, warm air holds more moisture than cold air. The warm moist air will leave the space you occupy through drafts, gaps, and by diffusion through the fabric of the building. If that warm moist air contacts a cold surface then the moisture in it will drop out as condensation, potentially causing damp and other problems.

The two routes to preventing this condensation causing a problem are, preventing air/moisture diffusion and providing ventilation.
- Installation of a vapor barrier on the warm side of the insulation prevents the moist air getting to the cold side, eliminating the potential for condensation
- Venting the cold side of the insulation will allow any condensation that may occur to evaporate overtime and thus prevent the issue.

Ideally you would incorporate both of these considerations into a design, so if the vapor barrier fails, or has a installation defect, then the ventilation on the cold side saves you.

When I built my workshop I put OSB on the outside of the framing, oops I didn't know. I'm now about to insulate and either:
1. Install insulation in the framing to full 4" depth with a vapor barrier on the inside and run the risk of interstitial condensation.
2. Install a batten at the back of the 4" framing cavity, pepper the OSB at the back of the cavity with holes, then install 3" insulation. With the aim of providing an air gap and ventilation to the back of the insulation.

I've decided to go with option 1. My rational is I use my workshop for little time during the week, and then perhaps 8-12hrs on the weekend when I'm lucky. This pattern of usage means it has lots of time to dry out if condensation occurs. Additionally I plan to install a vapour barrier, and plywood as the inside facing, this will give effectively two barriers to moisture movement.

Fitz.