Loft Insulation

What loft insulation is

Loft insulation is a layer of material laid across the loft floor (or, in some cases, at rafter level) that slows the movement of heat between your heated rooms and the cold roof space above. Warm air rises, so without it a large share of the heat you pay for escapes straight through the ceiling and out through the roof.

How heat is lost through the roof

As much as 40% of a home’s heat can be lost through an uninsulated roof — more than through any single wall. Insulation does not create heat; it holds onto the heat you already have, so your heating does not have to work as hard to keep rooms comfortable.

When a new installation is suitable

If your loft is uninsulated, or has only a thin, patchy layer, a full installation is usually the single most cost-effective improvement you can make. It brings the loft floor up to a suitable depth in one go.

When a top-up is suitable

Many homes already have some insulation, often laid decades ago and now too shallow. Where that layer is dry and sound, a top-up builds it up to a suitable depth without starting from scratch.

When removal is needed

Sometimes the existing material is the problem. Wet, mouldy, rodent-contaminated or heavily compressed insulation is best taken out rather than covered over — see loft insulation removal. Not every old installation needs removing, though; we will tell you plainly when a top-up will do.

Choosing a material

No single material suits every loft. The main options are mineral wool for value and availability, sheep wool for older, more breathable roofs, recycled plastic for lower-irritation handling and sustainability, and multifoil for rafter-level situations with limited depth. The right choice depends on the roof and loft, not on the property age alone.

Property-age suitability

A Victorian terrace, a 1930s semi and a post-1965 home each behave differently in the roof. Our property guide explains what to expect by age and construction.

Depths and product specifications

For wool-based loft floors, 270mm is the commonly used benchmark — usually a layer between the joists and a thicker layer laid across them to reduce heat lost through the timber. It is a rule of thumb for wool, not a figure to apply to every product; foil systems and rigid boards have their own specifications.

Ventilation and condensation

Insulation and airflow work together. Adding insulation makes the loft colder, so the eaves must stay clear and ventilation is considered alongside the work. Where there are signs of damp, we look at the cause — insulation alone will not fix a moisture problem.

Storage and raised boarding

If you want to keep using the loft for storage, boards must not crush the insulation. A raised boarding system lifts the deck above the build-up so its depth — and its performance — is preserved. Boarding a loft does not turn it into a habitable room.

The installation process

We work in six clear stages, always providing a written recommendation and quotation before any work is agreed. Access is protected, the loft inspected, measurements taken, the build-up installed, and the space left clean and documented.

Benefits and potential energy savings

Good loft insulation reduces heat loss, improves comfort in winter, and can lower heating demand and bills. It may also help with an EPC rating and reduce carbon emissions. The exact benefit varies: actual savings depend on the property, current insulation, heating system, energy use, installation quality and energy prices. Figures should be treated as general guidance from sources such as the Energy Saving Trust (accessed July 2026) rather than a promise for your specific home.

Factors affecting cost

Cost depends on the loft area, access, whether old material needs removing, the material and build-up chosen, and any ventilation or boarding work. Our cost guide explains the factors, and an assessment gives you an accurate written quotation.

Access, preparation and safety

Lofts vary from generous and boarded to cramped with awkward access, old wiring and stored belongings. We discuss what to clear beforehand, keep clearances around downlights and flues, protect pipes and tanks, and never work around hazards that should be dealt with first.