Done right, insulation turns a freezing summerhouse-of-a-shed into a room you'll happily sit in all year. Done wrong, it quietly rots the timber from the inside. Here's how to do it right.
To insulate a shed: create a frame of studs or battens, fit insulation snugly between them (PIR board for slim/high performance, mineral wool for cheap, multifoil for tight spaces or metal sheds), add a vapour barrier on the warm inside face, leave a ventilation air gap, and line over with OSB or ply. Insulate the walls, roof and floor, and draught-proof the doors.
Insulating a shed isn't complicated, but there's one bit nearly every quick guide skips — and it's the bit that decides whether your shed lasts. Get the vapour control and ventilation right and a cheap roll of mineral wool will serve you for decades. Get it wrong and the best insulation in the world will trap moisture and rot your frame. We'll cover both the how and the why.
As an Amazon Associate, ShedGuide earns from qualifying purchases. The product links below go to Amazon UK and help keep this guide free — they never change what you pay. For big rigid boards a local builders' merchant is often cheaper and saves on delivery; Amazon is handy for tapes, membranes, battens and smaller bits.
Be honest about how you'll use it before you spend a penny.
Set your expectations honestly: insulation slows heat loss — it doesn't generate heat. An insulated shed warms up fast and holds it, but you'll still want a small heater for winter use. What insulation really does is make that heater cheap to run and stop the place feeling like a fridge the moment you switch it off.
Three materials cover almost every shed. Here's the honest comparison, with rough 2026 DIY prices.
| Material | Warmth per mm | Rough cost | Best for |
|---|---|---|---|
| PIR rigid board (Celotex/Kingspan) | Best — slimmest | £20–35 per 2.4×1.2m sheet (50mm) | Tight stud depth, top performance |
| Mineral wool (rockwool/glasswool) | Good — needs more depth | £15–25 per roll/pack | Cheapest, also good for sound |
| Multifoil (foil quilt) | Modest — but very thin | £25–45 per roll | Shallow spaces, metal/plastic sheds |
Skip the false economies. Bubble wrap and thin expanded polystyrene get suggested a lot because they're cheap — but they insulate poorly and you'll be disappointed. If budget's tight, more depth of mineral wool beats a thin layer of something gimmicky every time.
This is the most important section on the page. Read it before you buy anything.
Insulation without vapour control rots your shed. Warm air carries moisture (your breath, a heater, a kettle). If that warm, damp air can drift through the insulation and hit the cold timber behind it, it condenses into water inside the wall — where it can't dry out, and where it quietly rots the frame. Cheap guides leave this out. It's the difference between a shed that lasts 20 years and one that's spongy in five.
Three rules keep moisture under control:
A breathable membrane behind the outer cladding sheds wind-driven rain but lets any moisture in the structure escape outwards. New build? Fit it as you clad. (See the cladding guide.)
A 1000-gauge polythene vapour barrier stapled across the inside of the insulation stops interior moisture getting in there in the first place. Lap and foil-tape every join — a barrier with holes isn't a barrier. Foil-faced PIR taped at the joints can double as the vapour barrier.
Leave a ventilation gap (at least 25mm) between insulation and the cold outer skin — especially in the roof — so anything that does get through can dry. And ventilate the room itself: an air brick or trickle vent, or just opening up regularly. A sealed, unventilated shed is a condensation trap no matter how well insulated.
Remember the order, outside-in: cladding → breathable membrane → air gap → insulation between studs → vapour barrier → inner lining. Warm vapour barrier inside, breathable membrane outside. Never the other way round.
The bread-and-butter job. You'll want CLS battens if your shed has no proper studs to insulate between.
Use the existing wall studs, or fix CLS battens to the inside of the cladding to create regular bays the depth of your insulation. Even spacing makes cutting the boards far easier.
Cut PIR board or mineral wool a whisker oversize so it wedges in with no gaps. Gaps are cold bridges — they waste heat and invite condensation. A bread knife cuts mineral wool; a fine-tooth saw or sharp blade does PIR.
For rigid board, seal every joint and edge with foil insulation tape so warm air can't sneak through the gaps and dump its moisture behind the board.
Staple a continuous polythene vapour barrier across the warm inside face, lapping and taping joins. This is the step that protects your timber — don't skip it.
Screw OSB or plywood over the battens. It protects the insulation, gives a tidy finish, and — unlike plasterboard — lets you fix shelves and a tool wall anywhere.
Most heat escapes upwards, so the roof matters most — and it's where the ventilation gap is non-negotiable.
Working from inside, cut PIR board or mineral wool to fit snugly between the rafters. PIR earns its keep here where rafter depth is shallow.
Keep at least a 25mm gap between the insulation and the underside of the roof deck/felt. Never pack insulation hard against the felt — that's the classic way to rot roof timbers. The gap lets the cold side breathe.
Add a vapour barrier across the warm face (or rely on taped foil-faced PIR), then line with thin OSB or ply. A multifoil layer is a good shallow-space option here, fixed with an air gap on each side.
Building the roof from scratch? Get the structure and felting right first in the roof guide, then come back to insulate it from inside.
An uninsulated floor is a cold floor — and easy to sort, ideally before the shed's full of stuff.
If you can get at the floor joists, drop rigid PIR board between them, resting on battens, with the floor deck over the top. On a new build, do this before you lay the floor — it's far easier. This keeps the insulation protected and the floor flush.
Can't lift the floor? Lay thin rigid board over the existing deck and put a new floor of OSB or ply on top. You'll lose a little headroom and a step up at the door, but it's quick and effective.
Planning a new build and want insulation designed in from the start? The free 8×6 shed plan (PDF) shows the floor and frame build-up — or grab the £9 three-size pack (6×4, 8×6, 10×8).
You can insulate a shed for next to nothing if you're resourceful — with a few honest caveats.
Don't bother with: bubble wrap, foil-backed cardboard, or thin polystyrene as your main insulation. They're cheap for a reason. If money's the constraint, fit a smaller area properly rather than the whole shed badly.
A different beast — condensation-prone and awkward to fix things to.
Metal and plastic sheds have no timber frame to insulate between and no breathability, so they sweat with condensation on cold mornings. You can improve them, but manage expectations:
Fix thin battens to the inside (self-tapping screws or strong adhesive for plastic) and run multifoil insulation across them, keeping an air gap on both sides. Multifoil suits these sheds because it's thin and reflects radiant heat.
The instinct is to seal every gap; resist it. A metal or plastic shed needs airflow or trapped moist air will run with condensation. Keep the vents clear, or add one.
Can you insulate a wooden shed more easily? Yes — timber gives you studs to work between and a structure that breathes, which is why everything above is written around it.
Turning a shed into a garden office, gym or workshop you'll use through winter? Insulation is step one of four.
Walls, roof and floor — a single uninsulated surface undoes a lot of the benefit. Don't stop at the walls.
Heat leaks fastest around doors and windows. Fit draught-excluder strip and check the seals — see doors & windows.
A small heater in a well-insulated shed is cheap to run. Electrics must be signed off by a Part P electrician — the finishing guide covers it.
"Insulate a shed to live in"? Using a building daily as an office or studio is fine. Actually sleeping in it as living accommodation is a different matter and usually needs planning permission and building regulations approval. Check with your council before you go that far — see planning.
Mineral wool is the cheapest mainstream option — you just need more depth. Cheaper still is reclaimed PIR offcuts, but you must still fit a vapour barrier and ventilation. Bubble wrap and thin polystyrene are cheap but barely insulate.
Yes — multifoil held off the inner skin with thin battens to keep an air gap, plus plenty of ventilation. They're condensation-prone, so never seal them up tight.
Insulate between the rafters but leave a 25mm air gap to the roof deck/felt so moisture can dry. Add a vapour barrier on the warm face, then line with OSB or ply. Never pack insulation against the felt.
PIR rigid board for the most warmth in the least thickness; mineral wool for cheap and quiet; multifoil for very shallow spaces and metal sheds. For most timber sheds, PIR between the studs is the sweet spot.
You can insulate one for comfortable year-round use as an office or workshop. Actually living/sleeping in it usually needs planning permission and building regulations — that's separate from daily use.
It helps, but only with a vapour barrier on the warm side and ventilation. Insulating without those makes condensation worse by trapping moist air against cold timber.
Paint, electrics, heating and storage — the finishing touches that make a shed somewhere you want to be.