Insulating a Timber Shed

Huggy_Bear

Morning all

Can someone help me understand the best approach to insulating a garden shed. Its made from wooden stats and 2x3 studs which I think are all standard widths. So its already built. I plan to use the space as a workshop all year round so I'm looking at a couple of options to insulate the walls but I'm confused about the need for damp proof membrane - I've never done this before so my knowledge is limited but I've used youtube lots

I'm looking at either using Kingspan thermapitch insulation board 25mm from a high street chain or 25mm Polystyrene boards but do I need a damp proof membrane as well and where does it go - as the shed is already built would it need to be cut to length and placed between the 2x3 studs and then the insulation boards.

Many thanks

FreeBear

Huggy_Bear said: I'm looking at either using Kingspan thermapitch insulation board 25mm from a high street chain or 25mm Polystyrene boards but do I need a damp proof membrane as well and where does it go

Use the Kingspan/Celotex type boards. When fitting between the studs, use expanding foam to fill any gaps between the studs & insulation - Get yourself an applicator gun - Much easier to lay down a thin bead and get the foam where it is needed.

The Vapour Control Membrane traditionally goes on the inside covering the studs & insulation boards and is then topped off with what ever material you are lining the walls with (plywood or plasterboard). But unless you insulate the ceiling and floor, the shed will remain cold and prone to condensation.

xyz123

Huggy_Bear said:

Morning all

Can someone help me understand the best approach to insulating a garden shed. Its made from wooden stats and 2x3 studs which I think are all standard widths. So its already built. I plan to use the space as a workshop all year round so I'm looking at a couple of options to insulate the walls but I'm confused about the need for damp proof membrane - I've never done this before so my knowledge is limited but I've used youtube lots

I'm looking at either using Kingspan thermapitch insulation board 25mm from a high street chain or 25mm Polystyrene boards but do I need a damp proof membrane as well and where does it go - as the shed is already built would it need to be cut to length and placed between the 2x3 studs and then the insulation boards.

Many thanks

What are you trying to achieve with insulation ? As mentioned, unless you propey insulate entire shed including floor and ceiling it maybe a waste of money... 

Homer_home

xyz123 said:

Huggy_Bear said:

Morning all

Can someone help me understand the best approach to insulating a garden shed. Its made from wooden stats and 2x3 studs which I think are all standard widths. So its already built. I plan to use the space as a workshop all year round so I'm looking at a couple of options to insulate the walls but I'm confused about the need for damp proof membrane - I've never done this before so my knowledge is limited but I've used youtube lots

I'm looking at either using Kingspan thermapitch insulation board 25mm from a high street chain or 25mm Polystyrene boards but do I need a damp proof membrane as well and where does it go - as the shed is already built would it need to be cut to length and placed between the 2x3 studs and then the insulation boards.

Many thanks

What are you trying to achieve with insulation ? As mentioned, unless you propey insulate entire shed including floor and ceiling it maybe a waste of money... 

Dont forget about the door!

You will also need to heat it as the thin insulation you will be using wont make a huge difference and dont forget about condensation too

Huggy_Bear

Thank you for all the comments. I plan to do the ceiling, floor and door too, but I wanted to understand about the walls first.

The goal is to make the shed usable all year as a workshop so realise I have to do the entire shed but my budget will not allow me to do this is one go. So I except I will be cold.

Back to the walls .....so the boards go on between the studs and any gaps filled with foam (there is already some of that around the ceiling boards) then I lay over the vapour membrane and then fix up sheet material fixing to studs.

What would happen if I didnt use the vapour membrane? Just boards and then sheet material (assume here I will do the floor and ceiling the following year).

FreeBear

Huggy_Bear said: What would happen if I didnt use the vapour membrane?

Any moisture inside the shed would penetrate the timbers - But you'll also get moisture from the outside wicking through. The insulation boards will act as a VCM to a certain extent, so you shouldn't get any appreciable moisture wicking through in either direction. Personally, I wouldn't bother adding a VCM in a shed.

Huggy_Bear

FreeBear said:

Huggy_Bear said: What would happen if I didnt use the vapour membrane?

Any moisture inside the shed would penetrate the timbers - But you'll also get moisture from the outside wicking through. The insulation boards will act as a VCM to a certain extent, so you shouldn't get any appreciable moisture wicking through in either direction. Personally, I wouldn't bother adding a VCM in a shed.

Ok thank you - I'm going to use the space as a woodworking workshop so there will be quite a bit of ventilation with the doors and windows open which I assume with help with moisture.

FreeBear

Huggy_Bear said:  I'm going to use the space as a woodworking workshop

Give your tools and any bare steel a wipe down with a rag and a bit of wax or oil - I use Waxoyl on some of my (metalworking) tools. Helps keep the rust at bay.

Valuable precision measuring tools, I keep indoors.

whatsthenews

Huggy_Bear said:

Morning all

Can someone help me understand the best approach to insulating a garden shed. Its made from wooden stats and 2x3 studs which I think are all standard widths. So its already built. I plan to use the space as a workshop all year round so I'm looking at a couple of options to insulate the walls but I'm confused about the need for damp proof membrane - I've never done this before so my knowledge is limited but I've used youtube lots

I'm looking at either using Kingspan thermapitch insulation board 25mm from a high street chain or 25mm Polystyrene boards but do I need a damp proof membrane as well and where does it go - as the shed is already built would it need to be cut to length and placed between the 2x3 studs and then the insulation boards.

Many thanks

I can only tell you what we've done when insulating our single brick (110mm thick) utility room to meet building reg's.
Obviously you won't need to worry about building reg's, but some principles still apply
1. we used foil backed/faced celotex which we bought online.Roughly the same u values as Kingspan , but cheaper.Reticel is also an option with the same u values as Celotex.
Recommend wearing a mask when you're cutting it, as it gets everywhere including up your nose and in your mouth. Gives me sinus type headaches if I don't use a mask.
Polystyrene doesn't have anything like the same u values as PIR boards.
2. because we only had 110 mm single thickness, we were required to have an airgap between the brick and the PIR boards. This is to stop any moisture that might arise in the outside wall coming in contact with the PIR boards
Would have thought that you should do the same with wood as the risk is even higher accounting for the depth of the slats and potential gaps between. Most people leave an airgap when they use it in cavity walls.
We had to fix 3 x 2 treated  battens to the brickwork.Damp proof membrane on the edge which was fixed to the masonry. Cut 50 mm PIR boards to size and friction fit them between the battens whilst maintaining a 25 mm air gap (we fixed small bits of timber to the sides of the battens to stop the PIR boards at 50mm. They have a tendency to tilt /twist when trying to fit them and this helps a lot .
I think you could do the same thing with your 25 mm ,leaving a 50 mm air gap, although you'll get much better insulation from 50 mm -we're also putting plasterboard with 25 mm insulation backing across the battens for the walls, and 50 mm  plus 50 mm in the ceiling. 
Don't know how high the risk of any water blowing in and managing to reach the back of the PIR boards is, but if it's a concern then maybe staple DPM to the inside of the slats, but the studs would still be at risk of moisture. Maybe there's a paint on product you could use to stop any moisture from the outside of the studs getting through to the PIR boards?
3. Our slab floor has a DPM under it, but because the internal floor level is lower than the damp proof course level, we sometimes used to get some damp patches around the room where the walls meet the floor. We put DPM around the room, 60 cm up the walls and 60 cm across onto the floor before we put the battens on the wall to protect the walls and also the  50 mm PIR that's going on top of the slab.

4. once all the PIR boards have been friction fitted,any gaps and the edges are all taped with foil tape, and then a vapour barrier covers the whole lot , including the timber battens and noggins.Stapled to timber and again edges and staples taped with foil tape. Pay particular attention to anywhere that pipes/cables come through the wall.
Apparently the biggest risk with internal insulation is interstitial condensation ie warm moist air from inside the room (on the warm side of the insulation), finding it's way through any gaps in the insulated part of the wall, onto the cold side, and then condensing in the wall and causing PIR/timbers to rot and damp coming through to the inside of the wall.
It's a faff! 
Of course this is us bringing the utility room in to the thermal envelope of the main house as we're putting a radiator in, and plasterboarding over the top of the insulation. We're planning on putting a TV in there for the winter as it'll probably be the warmest room in the house. We noticed a big difference even having just put the 100 mm in the ceiling. Not only was it warmer , but it didn't overheat with the sun anymore.

Like others have said, you need to think about if you're going to have a heat source in there and whether 25mm is enough isnulation. The insulation won't warm the room, it'll just reduce heat loss and gain. If you're insulating the walls you really need to insulate the roof too.

FreeBear

whatsthenews said:  Recommend wearing a mask when you're cutting it, as it gets everywhere including up your nose and in your mouth. Gives me sinus type headaches if I don't use a mask.

Apparently the biggest risk with internal insulation is interstitial condensation ie warm moist air from inside the room (on the warm side of the insulation), finding it's way through any gaps in the insulated part of the wall, onto the cold side, and then condensing in the wall and causing PIR/timbers to rot and damp coming through to the inside of the wall.

I found a sharp serrated kitchen knife to be the ideal tool for cutting foam boards - Gives a much cleaner cut than a hand saw, and less dust.

A wooden shed has a limited lifespan - 20 years is doing well. For that reason, I wouldn't get too hung up on preventing interstitial condensation or rot. Give the timber a good coat of preservative, and it should last.

fifthofwhisky

Sorry to jump in on this thread but it is an insulation topic. Regarding insulation of the floor, I have a shed base which is constructed of 27mm x 47mm (approx) with T&G over. Would there be any benefit in terms of improved insulation to put Celotex or similar between the 27mm x 47mm floor supports?