Slimming down

bwfNew guidance has been published by the British Woodworking Federation (BWF) to help firms placing orders for IGUs, including narrow cavity or ‘slim’ glass units.

‘Slim’ units have cavities of 8mm or less, often with a reduced edge seal, and are favoured in listed buildings or conservation areas as they allow thinner timber profiles and bead detail.

However, concerns have been raised by BWF members about the quality of some of these units supplied by a range of different manufacturers. Further investigation by the BWF has also highlighted that there are some ‘slim’ IGU suppliers who are seemingly unable to provide the appropriate test evidence required to ensure performance of the unit in the long term.

Kevin Underwood, BWF technical director, said: “We have received a number of queries through the BWF technical helpline and in our technical committee and council meetings concerning certain ‘slim’ insulating glass units on the market. The new guidance addresses this concern, helping buyers to exercise appropriate care and ensure that when purchasing IGUs they know what to ask for and what they should expect from supporting documentation from their suppliers.”

Kevin Underwood also pointed out that CE marking for glass units became mandatory on 1 July 2013, so this should help buyers of all types IGU that are covered by the harmonised standard BS EN 1279-5. “In order to establish that the test evidence applies to the glass units which you’re intending to buy, you should ask the supplier for a copy of the system description, and check that this is fully consistent with what you’re buying.

“The IGUs should also have been tested for durability, which means meeting the requirements for moisture penetration, gas leakage if appropriate, and edge seal strength. The production of the IGUs should also follow a factory production control system and periodic testing meeting the requirements of BS EN 1279.”

Members are also advised to discuss the length of warranty that is being offered by their glazing suppliers on these units and to check the detail as to what these warranties will cover. They should also confirm that they will employ an acceptable glazing method using appropriate and compatible materials in an effort to avoid future problems.

A copy of the BWF fact sheet on slim IGUs can be downloaded at:
http://www.bwf.org.uk/assets/bwf-igu-advice.pdf