How much heat does an uninsulated pipe lose?

A bare 22mm copper pipe carrying 60°C water in a 20°C space loses approximately 24.5 W/m. Over 20 metres, that’s 490W — almost half a kilowatt continuously wasted. At 2,000 hours per year, this costs approximately £68 in gas. Insulation reduces this by 75-90%.

What does BS 5422 require for pipe insulation?

BS 5422 specifies minimum insulation thickness for pipes based on diameter, fluid temperature, and location. For domestic heating pipes (60°C) in unheated spaces, typical minimums are 19mm for 15-22mm pipe and 25mm for 28-42mm pipe. Building Regulations Part L also sets requirements.

Do I need to insulate all heating pipes?

Building Regulations Part L requires insulation on heating pipework in unheated areas (loft, under floors, in walls, garages). Pipes within the heated envelope contribute useful heat and may not need insulation, though it’s still good practice to prevent heat reaching unintended areas.

What insulation material should I use?

Common materials include nitrile rubber (Armaflex, K-Flex) with thermal conductivity ~0.035-0.040 W/mK, and polyethylene foam (Climaflex) at ~0.038-0.045 W/mK. For higher temperatures (above 100°C), mineral wool or glass fibre sections are used.

How is pipe heat loss calculated?

For insulated pipes: Q = 2πkΔT / ln(r2/r1) W/m, where k is thermal conductivity, ΔT is temperature difference, r1 is pipe outer radius, and r2 is insulated outer radius. For uninsulated pipes, heat loss depends on pipe diameter and natural convection conditions.

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Pipe Heat Loss Calculator — BS 5422 Insulation

Calculate heat loss per metre by pipe diameter and insulation thickness. Determine annual energy loss cost and BS 5422 compliance.

Pipe Diameter

Pipe outside diameter

Insulation Thickness

Insulation wall thickness

Pipe Length

Total pipe run length

Fluid Temperature

Hot water / heating temperature

Ambient Temperature

Surrounding air temperature

How We Calculate This

This calculator determines heat loss from pipework based on pipe diameter, insulation thickness, and temperature conditions. It helps engineers comply with BS 5422 and estimate energy savings from insulation.

Formulas

Insulated loss (W/m): 2πkΔT ÷ ln(r₂/r₁)
Total loss (W): W/m × pipe length
Annual energy (kWh): Total W × hours ÷ 1000
Annual cost: kWh × energy price

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.