The heating's going back on, and so are the bills. On 1 October 2026 Ofgem's energy price cap rose by 4% to £1,723 a year for a typical dual-fuel household, and analysts are already forecasting a further rise in January 2027. For homeowners that's a reason to stop heat leaking out. For builders and installers it means one thing: the next few months are when insulation jobs land on your desk.
This guide is built for both. It covers which insulation to fit where this autumn and winter, which products from our range suit each job, and the cold-weather installation habits that separate a job that performs from one that ends in callbacks.
Why autumn is the insulation window
Insulation pays back fastest when it goes in before the coldest months, not halfway through them. There are practical reasons too:
- Drier sites. October and early November are usually kinder than January for anything involving open roofs, external walls or groundworks.
- Demand peaks later. Once the first proper cold snap arrives, everyone wants boards at once. Ordering now means you're not waiting on stock when the client is pushing.
- Bills compound. Every week a loft or wall stays uninsulated through winter is money the household won't get back.
What to fit, element by element
Heat leaves a home through the roof, walls, floors, windows and draughts. Here's how to tackle each part of the fabric, and the products we'd reach for.
1. Lofts: the quickest win
If the loft has less than the recommended depth (around 270mm of mineral wool), topping it up is still the cheapest, fastest improvement in most UK homes. Lay the first layer between the joists and the second layer across them to cut cold bridging through the timber.
Product to use: URSA 10 Diverso Loft Insulation Roll, a lightweight glass mineral wool roll that's easy to handle in a cramped loft.
Don't forget: keep eaves ventilation clear, don't squash the roll under boarding (compressed insulation performs worse), and insulate the loft hatch. We've covered lofts in depth in our 2026 loft insulation guide.
2. Pitched roofs and loft conversions: insulate at the rafters
Turning a loft into a warm, usable room means insulating between and under the rafters instead of at joist level. Space is tight here, so high-performance rigid boards earn their keep.
- Kingspan Kooltherm K107 Pitched Roof Board: a phenolic board that delivers a thinner build-up for the same performance, ideal where headroom matters.
- Kingspan Thermapitch TP10: a PIR board designed for pitched roofs, fitted between, over or under rafters.
- Mannok PIR Insulation Boards and Ecotherm PIR Insulation: versatile, cost-effective general-purpose PIR boards in a range of thicknesses.
Not sure which PIR brand to pick? Our Celotex vs Kingspan vs Mannok comparison breaks it down.
3. Rooms over garages and open passageways
A bedroom above an integral garage or a passageway is one of the coldest rooms in the house, because its floor is exposed to outside air from below. Insulating the soffit (the ceiling of the garage or passage) fixes this.
Product to use: Kingspan Kooltherm K110 Soffit Board, designed specifically for insulating underneath concrete soffits.
4. Cavity walls (new builds and extensions)
Extensions and new builds running through autumn and winter need cavity insulation that suits the wall design. Partial fill leaves a residual air cavity; full fill uses the whole cavity.
- Partial fill: Kingspan Kooltherm K108 Cavity Board and Kingspan Thermawall TW50.
- Full fill rigid: Kingspan Kooltherm K106 Cavity Board and Ecotherm Full Fill Cavity Wall Insulation.
- Mineral wool batts: URSA 35 Cavity Wall Batts and Superglass Superwall 36, non-combustible and budget-friendly.
Close cavities properly at openings and compartment lines. A product such as the Cavity Stop Sock Fire Barrier helps maintain fire separation in the cavity.
5. Solid walls: insulate inside or out
Older homes with solid brick walls lose a lot of heat through them, and there's no cavity to fill. You have two options.
Internal wall insulation is ideal for a room-by-room winter project. Mannok PIR Insulated Plasterboard combines insulation and plasterboard in one board, so you insulate and line the wall in a single step. Where you're building out a stud or batten wall, Kingspan Kooltherm K112 fits between and over the framing.
External wall insulation keeps internal floor space intact. External Wall Insulation EPS Board paired with a finish like K Rend Silicone TC15 gives a weatherproof, low-maintenance result. Read more in our solid wall retrofit guide.
6. Floors: stop the cold coming up
Cold floors are a common winter complaint, especially in extensions and ground-floor rooms. If a floor is coming up anyway, or you're laying a new slab or screed, insulate it.
- Kingspan Thermafloor TF70: a PIR floorboard for use under screeds or chipboard on ground-bearing and suspended concrete floors.
- Kingspan Kooltherm K103 Floorboard: a thinner phenolic option where floor levels are tight.
- EPS70, EPS100 and EPS150: cost-effective expanded polystyrene in increasing compressive strengths for floors under different loads.
7. Timber frame and stud walls
For timber frame walls, internal stud partitions to external walls or between rafters, flexible mineral wool friction-fits between studs with minimal waste.
Products to use: URSA 35 Timber Frame Roll and Rockwool Flexi Insulation Slab, whose flexible edge lets it spring into place between irregular studs.
Installing insulation in cold, wet weather: 7 rules
Winter jobs go wrong for predictable reasons. Get these right and the insulation will perform as designed.
- Keep it dry from delivery to fitting. Store boards and rolls off the ground, covered and out of standing water. Wet mineral wool loses much of its performance and should never be closed in damp.
- Check minimum application temperatures. Adhesives, foams, sealants and renders all have a lowest working temperature on their datasheet. Many renders and adhesives shouldn't go on when it's close to freezing or frost is forecast, so plan external work for the milder part of the day.
- Put the vapour control layer on the warm side. In winter, warm moist air inside the house pushes into the structure. A vapour control layer on the room side, with taped joints, stops it condensing inside the wall or roof.
- Tape and seal board joints. Rigid board performance depends on tight joints. Gaps let air (and heat) bypass the insulation.
- Don't block ventilation. Lofts and cold roofs need airflow at the eaves to prevent condensation. Insulating isn't the same as sealing up.
- Avoid cold bridges. Run insulation continuously around junctions, window reveals and floor edges. A small uninsulated strip can become a cold, damp patch that grows mould.
- Don't compress mineral wool. Squashing a roll under loft boards or into too narrow a cavity reduces its thermal performance. Use the right thickness for the space.
Looking further ahead: the Future Homes Standard
If you're pricing new-build or extension work, keep an eye on the Future Homes Standard. The regulations were published in March 2026 and come into force in England in March 2027, with a transition period for projects already in the system. Expect thicker insulation and better continuity of the building fabric to become standard. Specifying higher-performing boards today puts you ahead of the change rather than scrambling to catch up.
Plan your winter order
Next Day Insulation is an online-only supplier, so you get trade-range products without a trip to the merchant. Order before the cold snaps and the rush, and your materials can be on site the next day.
Buying in bulk for a bigger job? Many of our insulation products are available by the pallet. Call us on 07862 352788 for pallet pricing.
Autumn/Winter insulation FAQs
Is it too late to insulate before winter 2026?
No. Most loft, floor and internal wall jobs can be done in a day or two, and every month of winter that a home is better insulated is money saved on heating. Earlier is better, but it's never too late.
Can you install insulation in winter?
Yes. Internal work such as lofts, stud walls, floors and internal wall insulation is largely unaffected by the weather. External work like external wall insulation and render needs dry conditions and temperatures above the product's minimum, so plan around the forecast.
What's the best insulation for keeping a house warm in winter?
There's no single best product. It depends on where it's going. Mineral wool rolls are the go-to for lofts, PIR and phenolic boards give the best performance per millimetre where space is tight (rafters, floors, internal walls), and EPS is a cost-effective choice for floors and external walls.
PIR or phenolic: which should I choose?
Both are high-performance rigid boards. Phenolic boards (such as Kingspan Kooltherm) generally achieve the same performance at a slightly thinner thickness, which helps where headroom or floor levels are tight. PIR boards are usually more economical. Pick phenolic where every millimetre counts and PIR where it doesn't.
Where does a house lose the most heat?
In a typical uninsulated home, the walls and roof account for the largest share of heat loss, followed by draughts, floors and windows. That's why lofts and walls are usually the first jobs to prioritise.