Insurers are increasingly requiring non-combustible insulation in flat roofing systems, but architects sometimes end up specifying insulation that doesn’t comply. In this article we look at some of the things you should be aware of – read on to ensure you aren’t caught out.
What’s the requirement for non-combustible insulation?
The Building Regulations restrict the use of combustible materials in the external walls of buildings over 11m high with a residential purpose, including specified attachments such as balconies as they are considered part of the external wall. However, roofs and roof terraces on the same buildings are required (as assemblies) to achieve BROOF(t4) to BS EN 13501-5, and non-combustible insulation is not specifically required in flat roofing by the building regulations.
Nevertheless, some insurers, fire and building control officers are increasingly pushing for the use of non-combustible insulation in roofs and roof terraces as well as BROOF(t4) performance, and architects are, as a result, choosing to specify them.
Note that NHBC, Premier Insurance and LABC are not routinely requiring non-combustible insulation for roofs at this present time, in our experience.
What’s the problem?
Typically, non-combustible insulation consists of non-organic materials such as stone or glass-based products. These materials are typically Euroclass A1 in their basic form.
We are increasingly seeing architects specifying these products, but you should be aware that whilst the core material is Euroclass A1, not all the products produced by manufacturers from Euroclass A1 insulation will be Euroclass A1, for practical reasons.
For example, if an insulation board includes a facing material to allow for the bonding or torch application of membranes, the whole product may not be non-combustible. Some such products are useful to specify in areas of heavy traffic, such as where plant is installed on the roof. However, the facing material may not be A1 and in some cases may be Euroclass E, being a PE (polyethylene) or fleece facing.
Specifying these materials in some areas of your building design will not meet a requirement for non-combustible insulation.
The AccuRoof approach to non-combustible insulation
AccuRoof takes a pragmatic yet compliant approach to flat roofing, working with you to understand what your requirements are and how they might be met within your budget and other constraints.
Why do you need to use the board? If it is for fire safety reasons, are you aware of its fire classification? It is always helpful to check the technical data sheet.
Once we understand your requirements it is often possible to come up with a solution which meets them, whilst remaining compliant with the regulations and with the insurer’s and clients requirements. Here is an example.
196 – 222 King’s Road, Chelsea is a six-storey mixed use development we worked on with Wates Group. It includes several residential terraces and a rooftop restaurant. In this case the fire officer rejected the use of XPS (expanded polystyrene) insulation due to fire risk, instead requiring non-combustible insulation.
A supplier had recommended the architect specify a cellular glass board which included a Class E rated facer. We developed a solution which removed the need for a facer. Instead we used a non-faced, non-combustible board with hot melt waterproofing under and over the board. The hot melt product can stick direct to the board without the need for any facing material.
Advice for architects
- Make sure you know who the project-specific influencers are with regards to fire compliance; most notably the name of the building insurer and what the fire strategy is. This will help to design a roof system that will meet the requirements of all the key stakeholders.
- If your insurer, fire or building control officer or client requires that a roof build up is non-combustible, all the insulation in the build up will need to be non-combustible. There are solutions which allow for this.
- Check the technical data sheet for all the ‘non-combustible’ insulation products you want to specify to ensure that the product itself is entirely non-combustible (for example Euroclass A1), and not just the core material.
- Be aware that some Euroclass A1 insulation products may have higher Lambda values than XPS, EPS, or PIR insulation, for example, and therefore greater thickness would be required to achieve the same U-value. It is a good idea to ensure the right product choice happens early enough to avoid any practical challenges on site.
AccuRoof is here to give you the best available advice to meet your needs for genuinely non-combustible insulation. Get in touch if you think we might be able to help.
