I wish to comment on a statement made in the article ‘Plastic pipe for building services’ (BSj, 05/04, page 69) regarding the insulation of plastic pipes.

In the article the writer states ‘Plastic pipes have low thermal conductivity – this can reduce the need for insulation or, sometimes negate its use. This is often the case where insulation is required on traditional pipework to prevent condensation’.

This statement rather simplifies the situation and gives the false impression that significant savings can be made by reducing the level of insulation. The thermal conductivity of plastic pipes (0·16 – 0·22 W/mK) is low compared to copper (385 W/mK) or steel (63 W/mK) but is still high when compared with insulation (0·021-0·040 W/mK).

A plastic pipe wall thickness of 10 mm is therefore equivalent to approximately 1-2 mm of insulation. This is not significant enough to allow the insulation thickness to be reduced especially when it is recognised that pipe insulation is manufactured in 5 mm wall thickness increments.

BS 5422: 2001 does not make any allowance for the use of plastic pipes; failure to install the specified insulation thickness would not meet the standard’s requirements and therefore may contravene Part L of the Building Regulations.

The basis of BS 5422: 2001 is one of energy conservation and the resultant reduction of carbon dioxide emissions. Any lessening of the levels of insulation laid down in the standard is therefore contrary to the energy policy of the UK and Europe, never mind the law.