How to Insulate a Loft

Why Loft Insulation Matters

25% of heat in an uninsulated UK home is lost through the roof. The recommended depth for loft insulation in the UK is 270mm (mineral wool). Most older UK homes have inadequate insulation — less than 100mm — which is far below current standards.

Types of Loft Insulation

Mineral wool (glass or rock wool): most common and cheapest, £5–£10 per square metre DIY. Loose fill (cellulose or mineral wool granules): good for irregularly shaped lofts, blown in professionally. Rigid foam boards: used for warm roof insulation where loft is used as living space.

Cold Loft vs Warm Loft Insulation

Cold loft (unused loft): insulate the loft floor between and over the joists. Cheapest and most effective option. Warm loft (loft converted to living space): insulate between and over the rafters. More complex and expensive but creates a usable insulated space.

DIY Cold Loft Insulation — Step by Step

Clear the loft floor of any storage. Lay the first layer (100mm) between the joists. Lay the second layer (170mm) at right angles across the joists. Total 270mm. Leave the cold water tank and pipes accessible and ensure ventilation gaps at the eaves are not blocked.

Insulating the Loft Hatch

The loft hatch is a major heat loss point. Attach a layer of rigid insulation board to the top of the hatch cover (same depth as loft insulation) and fit a draught-proof seal around the frame. This is often overlooked but makes a significant difference.

Loft Insulation Grants UK 2026

The UK government offers free or subsidised loft insulation through the ECO4 scheme for qualifying households (low income, benefits recipients, or with an EPC of D or below). Contact your energy supplier or local council to check eligibility. The Warm Homes Plan also provides funding for energy improvements.