For Tenants, Homeowners, and Landlords in the United Kingdom.

This page outlines the insulation measures currently available under the Great British Insulation Scheme (GBIS). The information is intended for tenants, homeowners, and landlords who are eligible for energy efficiency support under GBIS.

Each insulation type is designed to reduce energy loss, improve indoor comfort, and support long-term reductions in heating demand. Only one measure may be funded per property under GBIS. All installations must be carried out by TrustMark-registered contractors and comply with PAS 2035 retrofit standards.

Loft Insulation

Loft Insulation refers to the placement of insulating materials on the floor of the roof space to prevent warm air from escaping through the ceiling.

System Overview:

  • Mineral wool rolls are placed between and across joists to the recommended depth (typically 270mm total).
  • Optional boarding may be installed above insulation for storage.

This measure provides a thermal barrier that slows heat transfer through the roof structure.

Suitability:
Recommended for all properties with accessible lofts and inadequate existing insulation.

Installation Duration:
2–4 hours for most standard homes.

Expected Lifespan:
Over 40 years with minimal maintenance.

Cavity Wall Insulation (CWI)

Cavity Wall Insulation involves filling the space between two masonry walls with insulating material to reduce heat loss.

System Overview:

  • Small holes are drilled into the external wall.
  • Insulation material such as mineral wool, polystyrene beads, or foam is injected into the cavity.
  • Holes are resealed post-installation.

The insulation reduces air movement within the wall, trapping heat inside.

Suitability:
Applicable to properties with uninsulated cavity walls, typically built between the 1920s and 1990s. A borescope inspection is used to assess suitability.

Installation Duration:
2–4 hours for a semi-detached house.

Expected Lifespan:
25 years or more; often guaranteed under the CIGA (Cavity Insulation Guarantee Agency).

Internal Wall Insulation (IWI)

Internal Wall Insulation adds thermal insulation to the inside of external walls in solid wall properties.

System Overview:

  • Rigid insulation boards or stud wall systems are installed on internal surfaces.
  • Insulation materials include mineral wool, PIR boards, or multi-layer composites.
  • The wall is finished with plasterboard and ready for decoration.

The system prevents internal heat loss through solid masonry.

Suitability:
Best for pre-1920s homes or where cavity wall insulation is not viable.

Installation Duration:
3–5 days depending on number of rooms.

Expected Lifespan:
30–40 years.

Room in Roof (RIR) Insulation

RIR Insulation targets converted attic spaces used as living areas, where significant heat loss can occur through sloped ceilings and adjoining walls.

System Overview:

  • Insulated boards or mineral wool batts are fitted between and over rafters.
  • Gable and dormer walls are insulated to reduce thermal bridging.
  • Finished with plasterboard for interior use.

Suitability:
Ideal for homes with habitable loft rooms or attic conversions.

Installation Duration:
1–3 days depending on layout and surface area.

Expected Lifespan:
Over 40 years.

Underfloor Insulation

Underfloor Insulation involves placing insulating materials between suspended timber floor joists to reduce heat loss through ground floors.

System Overview:

  • Mineral wool, rigid foam, or natural fibre batts are fixed beneath the floor.
  • A breathable membrane may be used to control moisture.
  • Access is usually gained via crawl spaces or lifted floorboards.

This reduces draughts and improves floor-level warmth.

Suitability:
Recommended for older homes with raised timber floors (typically pre-1970).

Installation Duration:
1–2 days depending on accessibility.

Expected Lifespan:
30–40 years.

Flat Roof Insulation

Flat Roof Insulation creates a thermal barrier on flat or low-pitched roof areas, often seen in extensions or blocks of flats.

System Overview:

  • Warm Roof: Rigid boards installed above the roof deck and under waterproofing.
  • Cold Roof: Insulation fitted between ceiling joists below the roof deck.

Materials may include PIR boards, mineral wool, or spray foam.

Suitability:
Used where flat roof areas have poor thermal performance and safe access is available.

Installation Duration:
1–3 days.

Expected Lifespan:
25–30 years.

Park Home Insulation

Park Home Insulation involves insulating the external walls, floors, and sometimes roofs of prefabricated homes or static caravans.

System Overview:

  • External cladding systems with insulation boards are applied.
  • Floor insulation is added below the unit.
  • Roof insulation may be installed internally or externally.

Suitability:
Specifically for permanent residents in park homes with low EPC ratings.

Installation Duration:
2–4 days.

Expected Lifespan:
20–30 years.

Each measure under GBIS is determined following a property survey by an accredited assessor. The most appropriate solution is selected based on existing insulation levels, cost-effectiveness, and carbon reduction value.

If you wish to apply for a GBIS-funded insulation upgrade, use The Consumer Rights’  GBIS Eligibility Checker to get started.