Since April this year, insulation on ductwork in non-domestic buildings must comply with new legislation. Didn't know? It's time to catch up.
When compared to its woolly-worded predecessor, the new BS5422: 2001 is a model of clarity. No more ambiguous phrases such as 'economic thickness' posing as a guide for designers. Today's standard gives precise thicknesses of insulation needed for ductwork carrying either warm air or cold air in non-domestic buildings.

At the heart of the new BS5422: 2001, lie a number of charts, which have now been given the teeth that were lacking in its predecessor. They are based on a rigorous analysis of environmental benefit and deal with thickness of insulation required. However, thickness is not everything, insulants should be assessed in three ways: can they one provide greater space efficiency; two be installed more easily; and three deliver cost benefits.

Space efficiency
The new BS5422: 2001 gives a very good indication of relative performance in the tables of thickness required for using a modern insulant as opposed to mineral fibre lagging.

It can be seen that a material, such as closed cell phenolic insulation, with a thermal conductivity of 0·018 W/mK will meet the standard for a 10°C temperature differential with a thickness of just 20 mm, while a typical mineral fibre insulant with a k-value of greater than 0·030 W/mK will need to be more than 50% thicker. The 22 mm wall thickness of phenolic pre-insulated ducting systems (as shown in the picture to the left) will easily meet the requirements of BS5422: 2001 for a 10°C temperature differential and therefore Approved Document L2 of the Building Regulations in England and Wales.

For systems designed to carry cold air, a principle of condensation prevention is applied with the ambient conditions set at +25°C still air temperature, 80% relative humidity, and a 21·3°C dewpoint temperature. The target figures here are for condensation control rather than heat loss, but the most efficient material is once again the closed cell phenolic insulation. And once again phenolic pre-insulated ducting readily complies.

However, insulant thickness is not the only factor in the space race. A sheet metal duct not only needs extra space to accommodate the added thickness of insulation required, but also to allow the installers to carry out the lagging operation.

Ease of handling
Pre-insulated phenolic ducting tips the scales at only 15% of the weight of sheet metal ducting. And because it is so much lighter, it comes to site in 3 m sections rather than 1·2 m or 1·5 m which means that it can be installed much faster than even unlagged sheet metal ducting. Those same weight advantages also bring serious benefits when it comes to calculating floor loadings, particularly in older buildings.

It is worth noting that rigid phenolic insulation is easier to install than mineral fibre. It doesn't require the use of duct masks and is not a skin irritant.

Cost advantages
Faster installation obviously carries implications of economy, even before any other factors are brought into the equation. But when material costs are added in, it is estimated that the installed cost of, for example, the Koolduct system, can be up to 10% cheaper than sheet metal ducting.

And in terms of operational cost, the superior insulation properties and minimal air leakage can yield electrical consumption savings of up to 20% because of the reduced heating and cooling loads.

So in all three areas of cost, ease of handling and performance, the phenolic insulation can demonstrate superiority over mineral fibre lagging. Add to that the benefits of Class O fire rating, negligible smoke emission and a pleasing aesthetic appearance and there can be no doubt that the modern technology is a route to top-class contemporary duct insulation.

For further information please: Tel: 01457 890 534, e-mail: technical.uk@insulation.kingspan.com. For Ireland: Tel: +353 (0) 42 97 95000 or e-mail: technical.ie@insulation.kingspan.com

A cpd presentation which addresses key issues such as running costs and environmental implications for all insulation related applications is available from Kingspan Insulation
To attend or arrange a cpd seminar, call Kingspan Insulation on 01544 387206.