The impacts of changing insulation specification on fire compliance
Are there any? Aren’t all insulation boards the same except that they’re made from either PIR, XPS, VIP, EPS, Stone Wool or Cellular Glass? The short answer is No.
The inclusion, or exclusion, of a fire retardant is an obvious difference that would affect the fire performance of an insulation board. This is as true for when in storage (see TC January 2022 QI@QI) as it is in application.
The addition of a facer, or a change of the facer, can also impact the fire performance of the insulation board; for example, adding a facer to class A1* ‘non-combustible’ FOAMGLAS changes the fire rating so the selection of the correct type of FOAMGLAS insulation for a project is important. The thickness of the insulation board does not generally have an impact on the BS EN 13501-1 reaction to fire rating performance but it can have a significant impact on the BS EN 13501-5 roof system rating.
If your supplier provides you with a Broof(t4) fire test classification report for a roof system including 50mm thick PIR insulation beneath 2 layers of Reinforced Bitumen Membrane (RBM), such a report does not apply to a roof build-up using 120mm thick PIR insulation. This is because the classification report is specific to the tested roof construction and because the insulation board thickness can, and does, impact the performance of the waterproofing membrane. To ensure that the fire test classification report is valid to the roof build-up you are installing, the stated construction within the report needs to match what you are laying, or the supplier needs to provide you with a CEN/TS 16459:2019 extended application (EXAP) report covering a range of insulation thicknesses.
Similarly, you cannot simply substitute a ‘non-combustible’ insulation board such as ROCKWOOL or FOAMGLAS beneath the waterproofing and expect a Broof(t4) to carry over from a fire test carried out on PIR insulation. Again, the insulation board can impact the waterproofing fire performance and specific testing of the roof construction is required.
Another key check to make when reading supplier fire test classification reports is the stated BS EN 13501-1 fire performance rating for the individual products. The full BS EN 13501-5 classification report for the roof system will provide the reaction to fire rating for each individual product. If the BS EN 13501-5 classification report states a product has BS EN 13501-1 E rating but the Product Data Sheet states the product is an F rating, the fire test report is no longer valid. We raise this as we are aware of a number of insulation products that have changed their fire test rating in 2022.
Next month: What are the impacts of the Building Regulations 2022 amendments?