5.1.21 Thermal insulation
Ground-bearing floors and walls below the DPC shall be thermally insulated to comply with building regulations and be suitable for the intended use. Issues to be taken into account include:
- floor insulation
- wall insulation
- thermal bridging.
Floor insulation#
Thermal insulation materials for use below ground-bearing slabs should have:
- appropriate density for the location
- low water absorption.
Insulation to be positioned below both the slab and DPM should be resistant to ground contaminants. The following materials are acceptable for use as insulation:
- expanded polystyrene boards (grade EPS 70) to BS EN 13163
- a proprietary material that complies with Technical Requirement R3.
Wall insulation#
Cavity insulation materials, super lightweight blocks, blocks with face bonded insulation or integral insulation should be:
- manufactured and used to comply with a British Standard and relevant code of practice, or
- used in compliance with Technical Requirement R3.
The thickness of materials for masonry cavity walls should be suitable for the required level of performance, see Clause 6.1.7.
Thermal bridging#
The design should ensure that any risk of thermal bridging is minimised, especially at junctions between floors and external walls. Precautions include:
- extending cavity insulation below floor slab level
- linking floor and wall insulation
- providing perimeter insulation to floors
- facing supporting substructure with insulation – where homes are stepped or staggered, the wall forming the step or stagger may require insulation
- particular attention should be paid to ensuring thermal bridging is addressed at door openings.
Last updated: 2nd January 2024