NHBC Standards 2011

8.1 Internal services

8.1 - Appendix 8.1A
   Thermal insulation of water pipes to delay freezing

Appendix 8.1-A

Thermal insulation of water pipes to delay freezing

Minimum insulation thickness (mm) needed to delay freezing inside domestic premises for cold water systems.
Outside pipe
diameter (mm)
Thermal conductivity of material at 0°C W/(m-K)
0.025 0.030 0.035 0.040
15 30 45 70 91
22-28 12 15 19 24
Notes:
The conditions assumed for the table are:
  • air temperature -6°C
  • water temperature +7°C
  • ice formation 50%

Examples of insulating materials
Thermal conductivity
W/(m-K)
Material
Less than 0.020 Rigid phenolic foam
0.020 to 0.025 Polyosocyanurate form and rigid polyurethane foam
0.025 to 0.030 PVC foam
0.030 to 0.035 Expanded polystyrene, extruded polystyrene, cross-linked polyethlene foam, expanded nitrile rubber and improved polyethylene foam
0.035 to 0.040 Standard polyethylene foam, expanded synthetic rubber and cellular glass


See table above for minimum thickness of insulation