Curtain walling and cladding

6.9

6.9.8Insulation

Insulation shall be suitable for the intended use.

Insulation should be:

  • in accordance with the design and the manufacturer’s recommendations
  • installed correctly to minimise the risk of thermal bridging, surface and interstitial condensation
  • securely fixed to the support frame or backing wall with appropriate fixings and/or adhesive in accordance with the manufacturer’s recommendations
  • returned into window and door openings, and continuous around penetrations through the wall
  • neatly cut around fixings and brackets.

Insulation materials should:

  • be inert, durable, rot and vermin proof
  • not be adversely affected by moisture
  • be one of the materials listed in Table 1.

Table 1: Materials for insulation

Insulation typeRelevant standard
Mineral woolBS EN 13162
FR grade (flame retardant) expanded polystyreneBS EN 13163
FR grade (flame retardant) extruded polystyreneBS EN 13164
Rigid polyurethane foam and polyisocyanurateBS EN 13165
Phenolic foamBS EN 13166
Cellular glassBS EN 13167
Other materialsTechnical Requirement R3

Reference should be made to BRE document BR135 – 2003 ‘Fire performance of external thermal insulation for walls of multi-storey buildings’ when specifying the type of insulation system to be installed.

Rainscreen cladding

The backing wall should be adequately insulated, particularly at exposed areas. Where open joints are used, a continuous and durable breather membrane should be provided over the outer face of the insulation.

Where the insulation is fixed to the backing wall, a minimum of one non-combustible fixing per 1m² or per insulation batt, whichever is the lesser, should be provided in addition to the other fixings.

Insulated render

A minimum of one non-combustible fixing per 1m² or per insulation batt, whichever provides the greater number, should be provided in addition to the other fixings. Non-combustible fixings should be fixed through the mesh reinforcement.

Insulation should be suitable to receive the render finish, and keyed where appropriate.

Brick slip cladding

Where the insulation is fixed to the backing wall, a minimum of one non-combustible fixing per 1m² or per insulation batt, whichever is the lesser, should be provided in addition to the other fixings.