When is non-combustible insulation not non-combustible?
On the face of it’s a bit of a strange question. Surely a non-combustible insulation board is simply non-combustible i.e., it does not catch fire or burn? However, from a fire test classification point of view, that is not true.
The boring bit
A product’s fire performance classification is defined within BS EN 13501-1. This is a specific classification standard for the product as it is sold.
A product like a roof insulation board undergoes 3 separate tests to achieve a classification:
• Non-combustibility test (EN ISO 1182)
• Single burning item test (EN 13823)
• lgnitability test (EN ISO 11925-2)
Based on the outcome of these tests an insulation product is classified based on:
• reaction to fire = A1 to F with class A1 or A2 being ‘non-combustible’
• smoke production = s1, s2, or s3
• flaming droplets/particles = d0, d1, d2
For example, the Pro Therm Rockface A2 upstand board is classed A2, s1-d0 as it does not burn but produces a small amount of smoke under test but there are no flaming droplets.
The real world
What this means in the real world- where QI and its customers operate – is that the Building Regulations require the use of an A1 or A2 classified product on any form of balcony over air (but not over heated space). Some balconies require insulating even though they are over air due to the structural design. On such projects the insulation board can only be either FOAMGLAS or ROCKWOOL as they are non-combustible insulants.
BUT, the only FOAMGLAS products that can be used are either T3+, T4+ or INVATHERM. All other FOAMGLAS products are not actually classified as class A1 or A2, they are actually classified as E which is the same rating as a PIR or XPS/EPS insulation. This is when a non-combustible insulation is not non-combustible.
The reason is the addition of a facer to the FOAMGLAS core. Whilst the core FOAMGLAS remains non-combustible the addition of the facer changes the results of the testing outlined above (the boring bit) and therefore the classification.
The interesting question comes when you have a client wanting a ‘non-combustible’ insulation within their warm roof construction (over heated space). This is not something required under the Building Regulations, but it is something some insurers require or a client may choose themselves. When these requests arrive, it is wise to discuss the exact requirement in detail with the client/insurer/main contactor as you can provide either ROCKWOOL or FOAMGLAS with a non-combustible core to meet that requirement, despite the official classification of the FOAMGLAS insulation product being class E. QI can assist you with those questions.
Next month: Amendments to ADB and impact on insulation