Non-combustible inverted roof insulation update

Since September 2019, we have produced 22 of these monthly QI@QI information articles, with three pieces covering the increasing demand for non-combustible insulation boards. So, where are we as we enter 2022 and await the outcome of the consultation on regulation 7 of Approved Document B.

In reality very little changed in the non-combustible insulation board market in 2021, other than FOAMGLAS® INVATHERMTM being accepted by the NHBC, as long as the below criteria are met. As the only non-combustible inverted roof insulation board in the UK market, this is an important step, aiming to achieve BBA certification for the product later this year.


• installed over the waterproofing layer with tight butted joints

• covered by a Water Flow Reducing Layer (WFRL)

• that the pedestals are certified for reaction to fire performance Euroclass ‘A1’ or A2’

• that the pedestals have a circular base with a diameter of at least 170mm and be supported by a rubber underlayment.

• the maximum load indicated in the Product Data sheets is not exceeded.

In the world of warm roofs FOAMGLAS® and ROCKWOOL® continue to be the only sources of non-combustible roof insulation board, with the penalty of a greater thickness for a given U-value versus PIR insulation, plus a greater cost that contractors should be conscious of when tendering projects.

One ‘grey area’ that was partly cleared up in 2021 was the requirements for non-combustible insulation on the upstands of a roof on a ‘relevant building’*. This clarity came courtesy of the joint NFRC/LRWA/SPRA Guidance Document that clarified the agreement reached for England with the Ministry of Housing Communities & Local Government (MHCLG) – now the Department for Levelling Up, Housing & Communities (DLUHC). Acceptance by the regulators in the other three nations needs to be confirmed locally.

The upstand rules for England are that non-combustible insulation board is required if:

• the upstand height is greater than 150mm above the roof finish/walking surface.

• the upstand insulation is thicker than 60mm.

• the upstand insulation spans across a compartment wall line.

• the upstand is against habitable space.

Copies of this guidance can be downloaded at:

* a ‘relevant building’ is one where there is a storey at least 18m above ground level that contains dwellings or institutions or a room for residential purposes (excluding any room in a hostel, hotel or a boarding house), student accommodation, care homes, sheltered housing, hospitals and school dormitories in buildings.