LRWA Insulation Subcommittee Update

The BS 6229:2018 – ‘flat Roofs with continuously supported flexible waterproof coverings’ – Code of Practice was published in November 2018. It provides an overall recommendation for the design, specification and, to a degree, the installation and later maintenance of a flat roof.

As you may be aware, the LRWA has taken stewardship of an Insulation Subcommittee to discuss and mediate the concerns of some members about the notes relating to the thermal performance of inverted roofs and blue roofs included in the recent update of BS6229. Whilst it has been identified that Polystyrene Insulation manufacturers currently do not have a representative body, LRWA took this position because we do represent manufacturers who provide inverted roof systems into the market.

It was great to see so many members interested in this issue who came to discuss the matter at a meeting back in June – and you can access the minutes of this meeting in the members area of the website. The aim of the group is to log the concerns of the committee with BSI and find a proactive and structured way forward to address some of the issues raised by the update.

One of the key areas that some members are concerned with relate to section Inverted Roofs. In the inverted roof, the inclusion of a WFRL (Water Flow Reduction Layer) immediately above the insulation layer is used to restrict the cooling effect of cold water reaching the waterproof layer. However, any shortcomings in this layer will affect the roof performance, therefore a note was added “Until further research and test evidence is made available and included as part of a future standard it would be prudent to increase the design thickness of the thermal insulation by not less than 10%.” Also note in Section, that no correction factor or reduction is permitted for Blue Inverted Roofs at all, even with a WFRL.

The LRWA have agreed to engage with the BBA/BRE to explore the possibility of developing a new test method to ensure the guidance for the thickness of insulation required is representative of the declared design U value.

Furthermore, the LRWA is also looking at drafting a new guidance note which will detail best practice for installation of WFRL’s to avoid poor detailing or workmanship including precautions through repair and maintenance. The document will provide an explanation of the note in BS6229, and can be used by all manufacturers.

At this stage, we also invite any other members who might be interested in getting involved in discussions about this issue and to be part of the new developments, to get in touch with CEO, Sarah Spink –