Hi, im debating what insulation to use for my garden cabin build.  My floor has 70mm PIR but i'm thinking about wool for the walls and ceiling.  My roof is a cold roof so will adhere to the air gap above the wool etc, but can the walls be full filled with wool?

Just wondering why wool?   It you want some natural/sustrainable and vapour permeable isn't something wood-fiber based potentially cheaper and also easier to work with?

On 13/10/2020 at 21:12, Mike_M said:

Hi, im debating what insulation to use for my garden cabin build.  My floor has 70mm PIR but i'm thinking about wool for the walls and ceiling.  My roof is a cold roof so will adhere to the air gap above the wool etc, but can the walls be full filled with wool?

 

Sheeps wool works brilliantly in a garden office. I repurposed an old summer house for our temporary office while building the house and insulated it with 100mm of sheeps wool in wall floor and roof. My wife works in it every day and feedback it that it provides an incredibly comfortable environment, summer or winter. During two winters, used every day of the week up to 12 hours per day there's never been a drop of condensation in the space. I'd use it in preference to the celotex/kingspan stuff any day ? The wall buildup is similar to a standard 'breathable' wall:

 

Inside:

Finished internal wall (whatever you prefer like plasterboard, plywood or some other panelling) I chose just to stick with the below 11mm OSB.

Service void (optional)

11mm OSB 3 (ideally taped at the seems but mine wasn't at the time) (osb acts as the vapour barrier but is hygroscopic so it allows the passage of moisture through the fabric of the building)
Sheeps wool insulation between battens and studs (if you have the space, then an extra layer of 50mm or more outside the timber frame works better - reduces cold bridging more effectively than extralayer internally - see Trada research for this)
Breather membrane
Ventilation gap
Cladding

 

With mine I took some shortcuts in just putting the sheeps wool into the old frame right up against the original cladding. Because of the nature of wool to buffer moisture, it has been fine, but for proper permanent build, I'd used the above buildup, which is what I'm using for my breathable walls and roof in my new house.

 

Last I look at prices, sheeps wool was cheaper per sqm than the wood fibre but that may have changed.

 

Below is a photo of the same buildup going into my new roof.

 

Hope that helps