A shed without insulation makes for a miserable workspace — freezing in January, stifling in August, and prone to damp year-round. The good news is that even basic insulation makes a dramatic difference, and you do not need to spend a lot of money to get there.
We’ve tested and written about shed insulation at length, and the honest answer is this: the cheapest effective method costs around £30 for a small shed, and the best-value complete solution comes in under £100. The right choice depends on how you plan to use the shed and whether you’re comfortable doing some DIY boarding.
If you’re also thinking about keeping the temperature stable once insulated, our guide to the cheapest ways to heat a garage or shed covers that separately.
Which shed insulation is cheapest? Quick summary
| Method | Cost per m² (approx.) | DIY difficulty | Best for |
|---|---|---|---|
| Foil-backed bubble wrap | £4–6 | Easy | Quick fix, rented sheds |
| EPS polystyrene boards | £3–5 | Easy–moderate | Walls and roof on a tight budget |
| PIR rigid boards (e.g. Celotex) | £8–12 | Moderate | Best thermal result per mm |
| Mineral wool roll | £5–8 | Moderate | Workshops, sound insulation |
1. Foil-backed bubble wrap — the easiest starting point
Plain bubble wrap is the most-talked-about budget option, and it does work — but only just. Standard bubble wrap has poor thermal resistance and will disappoint if you’re trying to use the shed through a proper winter. What you actually want is foil-backed bubble wrap, which combines air pockets with a reflective foil layer that bounces heat back into the space.
The SuperFOIL Shed Insulation Kit is the product we point people towards when they want to do this properly without overcomplicating it. It covers 21m² — enough for most 8×6ft or 10×8ft sheds — and includes aluminium tape for sealing the edges, a heavy-duty staple gun, and staples. No separate purchases needed, and installation takes an afternoon.
SuperFOIL Shed Insulation Kit (21m², Multi-Purpose Wrap + Fixings)
Best for: Sheds you want to insulate quickly without cutting and fitting rigid boards
- Single-bubble foil wrap: 3 rolls of 1m × 7m included
- Built-in vapour barrier — no additional membrane required
- Includes heavy-duty staple gun, staples, and 30m aluminium tape
- Covers walls, roof, and floor of a typical 8×6ft shed
Installation tip: Staple the foil to the interior framing, not the exterior cladding. Leave a small air gap between the foil and the cladding where possible — this improves performance and prevents condensation building up behind the wrap. Seal every edge and overlap with the included tape. This is the step most people skip, and it makes a significant difference.
2. Expanded polystyrene (EPS) boards — best for walls on a tight budget
EPS is the white foam you find protecting appliances in packaging. As insulation, it is underrated. It is lightweight, easy to cut with a serrated knife, moisture-resistant, and cheap. For a budget shed insulation project it sits between foil wrap and PIR boards in both cost and performance.
The key thing most buyers miss is that EPS comes in different grades. For shed walls and roofs, EPS 70 is the right choice — it has enough compressive strength to hold in wall cavities without compressing over time, and it is BBA certified for wall and floor use.
Triplast Expanded Polystyrene Foam Sheets EPS 70 (2400 × 1200 × 25mm)
Best for: Insulating shed walls and roofs where you plan to board over with OSB afterwards
- Full-height coverage: each board is 2400 × 1200mm, fitting most standard shed framing
- 25mm thickness works with standard shed framing depths
- BBA certified for wall and floor insulation
- Lightweight enough to install solo — no second person needed to hold boards
Installation tip: Cut the boards fractionally oversized and friction-fit into the framing cavities. EPS compresses slightly, which creates a snug, gapless fit. Run a bead of low-expansion foam around the edges before boarding over — any gap in the thermal envelope will undermine the whole job.
3. PIR rigid foam boards — best thermal performance for the money
If you’re converting a shed into a proper home office, gym, or workshop you’ll use year-round, PIR boards are the gold standard. They carry significantly better thermal values than EPS or foil wrap at the same thickness, meaning thinner boards achieve the same warmth. For a shed where every millimetre of internal space matters, that is worth paying for.
PIR boards carry a foil face on both sides, which acts as a built-in vapour barrier — no separate membrane is required. We recommend 25mm for walls and 50mm for the roof. The roof is where the most heat escapes, and the upgrade from 25mm to 50mm in that location costs relatively little but makes a noticeable difference in winter. Our detailed guide to fitting Celotex boards in a shed covers the full installation process.
PIR / Celotex Insulation Board 25mm (2400 × 1200mm)
Best for: Full shed conversions where you want the best thermal result within a tight framing depth
- PIR foam core with aluminium foil faces on both sides
- 25mm achieves approximately 1.25 m²K/W thermal resistance
- Significantly better than EPS at the same thickness
- Seal all edges with aluminium tape after fitting to complete the vapour barrier
Installation tip: PIR boards are rigid but will snap cleanly if scored with a Stanley knife and broken over a straight edge. Seal every joint and cut edge with aluminium tape before boarding — this is what separates a decent insulation job from an airtight one, and airtightness is where the real warmth comes from.
4. Mineral wool roll — the right choice for workshops
Mineral wool — sold under brands like Rockwool and Knauf Earthwool — is the fluffy insulation used in loft conversions and partition walls. In a shed, it earns its place in two specific situations: you need a fire-rated product because you’re installing electrics, or you want meaningful sound insulation for a workshop or music space.
It is genuinely good at both. The trade-off is that mineral wool is messier to work with than rigid boards, requires a separate vapour barrier, and works best in framing with enough depth to accommodate the thickness. For a basic garden shed you want to keep warm through winter, a rigid option above will usually be easier. For a dedicated workshop, Rockwool RW3 50mm slabs are worth the extra effort — the acoustic performance is noticeably better.
Rockwool RW3 Acoustic Insulation Slabs 50mm (5.76m² pack)
Best for: workshops, music rooms, or any shed where sound insulation matters as much as warmth
- 8 slabs per pack, 1200 × 600mm each — covers 5.76m², enough for one wall of a typical shed
- 60kg/m³ density — significantly better acoustic performance than lower density alternatives
- A1 Euroclass fire rating — non-combustible, safe to use around fixed electrical installations
- Water repellent — resists moisture build-up in an unheated shed environment
Installation tip: Mineral wool irritates skin — wear gloves and a dust mask when cutting. Cut with a sharp serrated blade, slightly oversized, and friction-fit between the framing. A separate polythene vapour barrier goes on the warm side before you board over — don’t skip this step or you’ll get condensation in the wall.
What about genuinely free options?
Yes — but with honest caveats. Old carpet, rugs, and thick blankets can add a small amount of thermal mass on the floor and against walls. They cost nothing if you have them to hand, and for a shed used mainly for storage, they can take the edge off the worst cold.
We would not recommend cardboard despite its popularity in online discussions. Cardboard absorbs moisture during wet weather and does not dry out quickly enough through winter — it ends up creating damp rather than solving cold. The free options are best thought of as a supplement, not a strategy.
Comparison table: shed insulation options at a glance
| Method | Approx. cost for 20m² | Vapour barrier needed | Fire rated | Boarding needed |
|---|---|---|---|---|
| SuperFOIL foil wrap kit | £85–95 (inc. fixings) | No (built-in) | Check label | No |
| EPS 25mm boards | £50–70 | Yes | Caution with electrics | Yes |
| PIR 25mm boards | £90–120 | No (foil faces) | Yes | Yes |
| Mineral wool 50mm | £50–60 per 5.76m² | Yes | Yes | Yes |
Three things that make the biggest difference
Whichever method you choose, these steps consistently improve the result.
Board over the insulation. Exposed foil wrap or EPS is vulnerable to damage and looks unfinished. OSB board is the cheapest and most practical option for covering the insulation and gives you a surface you can paint or panel over. Our guide to best materials for shed interior walls compares your options in detail.
Seal every gap. Insulation works by creating a continuous thermal barrier. A single unsealed gap — a cable entry point, an unfinished corner — undermines the entire job. Use aluminium tape on rigid board edges and low-expansion foam on any gaps in the shed structure itself. Our step-by-step guide to shed insulation includes a pre-start checklist worth running through before you begin.
Understand vapour barriers. PIR boards and foil-backed bubble wrap include a vapour barrier in the foil face. Mineral wool and EPS do not — a polythene membrane needs to go on the warm (interior) side of the insulation in those cases. If you’re unsure what applies to your specific shed type, our post on whether a garden building needs a vapour barrier covers this clearly.
What to avoid
Cardboard is often cited as a free insulation option. As noted above, it absorbs moisture and causes more problems than it solves in a cold, damp UK winter.
Spray foam is expensive — sometimes more than the cost of the shed itself — and completely unnecessary when standard board or roll insulation fits perfectly into the existing framing cavities.
Unlined wood boards on their own provide almost no thermal resistance. OSB and plywood are used to cover insulation, not replace it.
FAQ
What is the cheapest effective insulation for a shed?
Foil-backed bubble wrap is the cheapest ready-made product that produces meaningful results. The SuperFOIL kit at around £85–95 covers a full shed including fixings and is the best all-in-one option at the budget end.
Can I insulate a shed completely for free?
You can reduce heat loss using old rugs and blankets at no cost, but you will not achieve proper insulation. Free options are worth using on the floor as a supplement, not as the main method.
Do I need planning permission to insulate a shed?
No. Internal insulation work does not require planning permission in England and Wales, regardless of the materials used.
Which insulation is best for a shed used as a home office?
PIR boards (Celotex or equivalent) give the best thermal performance and are the right choice for year-round use. Pair 25mm boards in the walls with 50mm in the roof for the best result.
How long does it take to insulate a shed?
A weekend is realistic for most 8×10ft sheds using rigid boards or the SuperFOIL foil kit. Mineral wool takes slightly longer due to the additional vapour barrier step.
Does shed insulation help with condensation?
Yes — a well-insulated shed maintains a more stable internal temperature, which significantly reduces condensation. Sealing gaps and fitting a vapour barrier (where required) are equally important.
