Pipe Insulation

Pipe insulation – including the pipe insulation slab and pipe phenolic insulation – fully covers pipework, to limit heat loss, prevent freezing, and stop condensation forming on cold pipes.

What is insulation for pipes?

Pipe insulation is sometimes called pipe lagging. It refers to the rubber, foam, or rigid phenolic sections fitted over heating and water pipes.

The insulation maintains a steady temperature inside the pipe to stop hot water from cooling too quickly and to keep cold pipework from sweating.

Foiled back pipe lagging can be installed for added protection on areas exposed to heat, mechanical impact and moisture.

What is pipe insulation used for?

Pipe insulation is used:

• In lofts
• Under floors
• Inside stud walls
• In service voids and risers
• Around boilers and hot water cylinders
• In utility rooms, garages, and outbuildings
• Outdoors

It is also added:

• Behind kitchen units
• Behind shower mixers
• In suspended ceilings
• In basements and crawl spaces

Different types of pipe insulation

Here are the commonly available types of insulation for pipework:

Foam pipe insulation (Polyethylene)

Foam is mainly used for standard heating and domestic hot-water piping, household pipework, loft pipes that might freeze, and hot-water pipes that should not bleed heat into walls or floors. It also helps restrict heat loss along long runs of heating pipework.

Rubber insulation (flexible rubber tubes)

Some pipes get warm and make the air around them humid. Rubber insulation stops them from “sweating” and dripping everywhere. Rubber has a closed-cell structure with high vapour resistance.

Foil-faced pipe wrap

Not all pipes are straight. In messy corners or a valve cluster, sliding on a pre-shaped tube will not work – foil-faced wrap is the problem-solver.

It works similarly to ductwrap insulation in the sense that it wraps around irregular shapes, but pipe wrap is thinner and specifically designed for pipes. Simply wrap it around whatever shape you have and tape it shut.

Best for elbows, bends, and irregular shapes, areas where you cannot slide a full-length tube on, and boosting insulation on existing sleeves

Phenolic pipe insulation (rigid, high-performance shells)

Phenolic pipe insulation is firm, structured, and more engineered than the others. Best for systems with significant heat loss or that attract a lot of condensation, such as primary heating circuits.

Used in commercial spaces, plant rooms, long pipe runs, and areas where condensation would cause significant problems, or anywhere energy efficiency is a top priority.

Phenolic insulation is known for very low thermal conductivity (around 0.021–0.025 W/mK), which is why it is used in high-spec systems.

UV-resistant and weatherproof outdoor insulation

A tougher, denser version of foam or rubber, designed to survive outside, where normal indoor insulation would fall apart. Outdoor-rated pipe insulation usually includes a UV-resistant outer jacket that keeps the material from degrading in sunlight.

Best for any pipe outside the house, heat pump flow/return pipes, and garden tap supplies.

Others

Other insulation types, like ductslab insulation, are used for ducts but show how slab-style insulation works in larger runs. Ductslab is not used on round pipes; only on square or rectangular ductwork (included here for comparison only)

Benefits of insulation for pipes

Adding pipe insulation while the building is still open and unfinished prevents issues from arising later in the build. Here’s why it is worth doing early:

1. It stops heat loss before the walls close up. Hot water and heating pipes lose heat quickly when they are bare.
2. It prevents freezing, minimising the likelihood of frozen pipes, split pipes, or leaks when temperatures rise.
3. It prevents condensation and damp patches. That means no dripping, no damp marks on ceilings or walls, no mould forming in hidden places.
4. It can reduce noise from the plumbing system as hot pipes expand and cold pipes contract.
5. It protects pipes from physical damage as a result of being stepped on or bumped by tools and materials. 
6. It helps meet Part L requirements in unheated spaces – under floors, lofts, around boilers, near cylinders, and on long heating runs. Note that heating pipes only improve system efficiency when they run through unheated or cold areas.