Best Alternatives to Spray Foam Insulation in the UK
Mineral wool — the default UK choice
Glass or rock mineral wool batts at 270mm depth on the loft floor remain the standard UK loft insulation. Cost is £400–£1,200 fitted depending on property size. It meets current Building Regulations Part L, is breathable, non-combustible, and accepted by every lender. For most homeowners after a removal, this is the obvious first choice.
Sheep's wool
Sheep's wool batts perform similarly to mineral wool thermally and have the additional benefit of buffering humidity. Cost is roughly 2–3× mineral wool. It suits older homes with breathable construction and homeowners willing to pay a premium for natural materials.
PIR boards (Celotex / Kingspan / Recticel)
Rigid PIR boards are used between and below rafters when the loft is to be habitable. Boards must be installed with a continuous ventilation gap above so the rafters remain inspectable and ventilated. PIR delivers the highest U-value per millimetre of any common insulation, which suits restricted spaces. Lenders accept PIR provided installation follows the manufacturer's ventilation specification.
Wood fibre boards
Wood fibre boards are a breathable rigid alternative for room-in-roof situations, particularly in older or listed properties. They handle moisture more forgivingly than PIR and offer good summer thermal mass. Cost is higher than PIR.
Hemp and recycled cotton
Niche but growing options for homeowners prioritising low-carbon materials. Performance is comparable to mineral wool, cost is comparable to sheep's wool, and lender acceptance is good provided installation is documented.
What never to choose
Avoid any further sprayed polyurethane installation. Avoid loose-fill insulation that bridges eaves vents. Avoid any product whose installer cannot describe how the rafters will remain inspectable and ventilated.
Choosing between options
If the loft is non-habitable storage, mineral wool at ceiling joist level is the right answer for almost all UK homes. If you are converting the loft into a room, PIR or wood fibre between rafters with a maintained ventilation gap is correct. If breathability matters because the property is older or listed, sheep's wool or wood fibre wins.
Building Regulations and grants
All of these options can meet Building Regulations Part L when installed to the right depth. Some are eligible for ECO4 or Great British Insulation Scheme funding for qualifying households. A reputable installer will check eligibility as part of the quote.
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