How Much Pipe Insulation Do I Need?
Quick Answer
Measure total exposed pipe length — typically 20–30m for a 3-bed house
Standard bore sizes: 15mm and 22mm. Sold in 1m or 2m lengths. Include loft, garage, and external runs
Where to Insulate
Building Regulations and energy efficiency best practice require pipe insulation on:
- All pipes in unheated areas (loft, garage, under suspended floors)
- Hot water pipes from the boiler/cylinder to taps
- Central heating flow and return pipes in unheated spaces
- External pipes and pipes in cavity walls
Common Pipe Sizes in UK Homes
- 15mm (1/2″): Radiator feeds, basin/sink supplies
- 22mm (3/4″): Main heating flow/return, bath feeds
- 28mm (1″): Main boiler connections, cylinder feeds
- 35mm: Older gravity-fed systems
Insulation Thickness Requirements
Part L of the Building Regulations specifies minimum insulation thickness:
- Hot water pipes: Insulation thickness equal to pipe diameter (e.g. 22mm pipe = 22mm insulation)
- Frost protection only: Minimum 13mm wall thickness
Types of Pipe Insulation
- Foam tube (polyethylene): Most common, pre-slit, easy to fit
- Mineral wool wrap: For higher temperatures or irregular shapes
- Rubber tube (Armaflex): Professional grade, excellent thermal performance
Last updated: April 2026