Insulating a single skin shed

[Tomsbuild29]

I have bought a flatpack Garden room (Fancy shed) and it comes with floor insulation and roof insulation but not wall insulation. 

 

The walls are 42mm thick single skin wood. I'm trying to work out the best way to insulate it. 

 

I'm thinking about potentially insualting the outside off the wall as to not lose any internal space. My first thought would be to insulate and then screw battens through into the walls, then fix cladding to the battens. 

 

Do I need to consider an air gap, and a breather membrane? 

 

Does this sound like the best approach? 

 

Thanks in advance. 

[Redbeard]

Lots of considerations. Is it near a boundary? How close? Do you have Planning permission of is it within Permitted Dev'pt? 

 

Do you need non-flammable cladding? If so, what about a sheet insulation glued to the shed with cement-board over? Forget the battens. You should not necessarily need a membrane, depending on the materials you use, though using one on the outside of the insulation gives you 'belt and braces'. Ensure that all joints and perimeters of the insulation are tight and filled, or you may get thermal by-pass (cold air on the 'warm side'). You do not need an air-gap; indeed (as above) it could be your enemy rather than your friend.

[Iceverge]

On 26/11/2024 at 13:32, Tomsbuild29 said:

I'm thinking about potentially insualting the outside off the wall as to not lose any internal space. My first thought would be to insulate and then screw battens through into the walls, then fix cladding to the battens. 

 

Do I need to consider an air gap, and a breather membrane? 

 

This would work well.

 

With any building, espically a timber one I would be keen to see a robust drainage design so I'm disagreeing with @Redbeard here and saying that a vented cavity is required. 

 

If you're building for longevity and comfort I would attach a membrane to the walls, tape it to the base and the roof membrane if you can. Tape it to the windows and doors too to get a completely airtight building.

 

Something cheap like this will be fine. 

 

Add your insulation over the top. Anything will help but more will be better.  Ideally use 2 x layers of 50mm with the joints staggered, foamed and taped.  Then use 25*75mm strapping as battens held on with 6*160mm screws. 

 

Add your cladding over the top. 

 

Don't forget to add ventilation to the building as with the Airtightness you'll get a lot of moisture build up otherwise. 

[Redbeard]

47 minutes ago, Iceverge said:

With any building, espically a timber one I would be keen to see a robust drainage design so I'm disagreeing with @Redbeard here and saying that a vented cavity is required. 

 

Disagreeing is good! I think a lot will depend on the detailing and quality of work. Ventilated cavity is a belt-and-braces approach, and such approaches are good. Provided there is really good weather protection and a good roof oversail I think my suggestion will work, but @Iceverge's has an extra 'fail-safe'.

 

 

[JohnMo]

On 26/11/2024 at 13:32, Tomsbuild29 said:

walls are 42mm thick single skin wood

So a log style building. Be aware of the contraction, you must not have battens etc joined across multiple logs without a sliding joint. Failure to that leads to the logs being split, and or big gaps forming.

 

https://forum.buildhub.org.uk/topic/31017-summer-house-insulation/

 

 

[Redbeard]

Further variables:

 

Heated or unheated?

 

Is the roof oversail big enough to accommodate 'EWI'. If not you need either to re-roof or 'improvise', and the latter is not necessarily good.

 

 

4 minutes ago, JohnMo said:

So a log style building. Be aware of the contraction,

 

Good point.

 

@Iceverge, thinking about your lay-up. The ventilated cavity is formed by the 25 x 75 battens, yes? What insulation had you in mind, or just any rigid insulant?