September 2019

“Fire safety is a sensitive topic and
a lack of confidence about how
materials work individually and
when combined in a system is
understandable”
5How is resistance to fire spread declared for roofs? A roof’s
resistance to external fire exposure, in terms of fire spread across the
surface and penetration through the construction, is classified
separately in accordance with EN 13501-5. A roof can be rated one of the
following, from best to worst: BROOF(t4), CROOF(t4), DROOF(t4), EROOF(t4), or
FROOF(t4).
EN 13501-5 refers to four separate roof tests, detailed in ENV 1187. The (t4)
refers to the use of test 4, which is the only one sufficiently rigorous to
demonstrate compliance with UK fire safety requirements. The performance
rating of a roof typically dictates how far from a boundary or another building
the particular construction may be used.
6How should fire performance declarations be applied? Fire safety
is a sensitive topic and a lack of confidence about how materials work
individually and when combined in a system is understandable.
The more complex the building, the more specific the requirements in terms of
fire safety and performance. Applying general principles to buildings where
specific provisions are required risks compromising fire safety.
Where flat roofs are concerned, BS 6229:2018 provides useful guidance and
depending on the level of complexity, advice may also be sought from a fire
engineer or other specialist. Some projects, meanwhile, require consultation
directly with the local fire service.
‘All Inverted Roof
Insulation achieves the same U value at a given
thickness...’
In the past this may well have been the case. There were fewer
manufacturers, using similar blowing agents and much less
challenging U value targets.
However, environmental pressures led to a required change in
blowing agent technology from CFC’s and HCFC’s to Recycled CO 2 ,
which although greener and cleaner led to higher lambda values and
consequently greater thickness required to achieve the same U values
as before.
Pressure continued, with ETAG 031 and other regulatory legislation
leading to the assessment of the effects of rainwater cooling and freeze
thaw cycles. The industry began looking at design lambdas which
addressed these issues and through new technologies such as the
introduction of water reducing layers, the lamination of thinner more
addition of new constituents such as graphite manufactures, over time,
achieved thinner solutions.
Which leads us to the latest and perhaps greatest innovation in
Extruded Polystyrene (XPS) technology to date. Ravago, have launched
XENERGY TM ULTRA TM . Developed to deliver improved thermal
thicknesses of the past.
So what does that mean to our original question? Does all Inverted
Roof Insulation still achieve the same U value at a given thickness?
If we look at 0.15 W/m 2
TM
TM ULTRA
achieves this target in only
175mm, 30mm thinner than Ravago’s own previously best solution
TM SL) and almost 50mm thinner than most other XPS
Solutions and at 0.1 W/m 2 TM ULTRA
TM is only 260mm
(2x130mm), 60mm thinner than most alternative XPS solutions and up
to 95mm thinner than most EPS (Expanded Polystyrene) Solutions.
Then the answer is now emphatically NO!
With a design lambda of 0.028 W/mK and U value targeted
thicknesses
TM ULTRA TM has radically changed
how we look at product comparisons. We can no longer make price
comparisons based on cost £/m 3 , we now need to look more closely at
price £/m 2 of any product to achieve any given U value!
Next month’s QI by QI:
‘The myth about non-combustible insulation being required in
inverted roofs...’
Contact Polyfoam XPS
01429 855120
https://polyfoamxps.co.uk
@PolyfoamXPS
SEPTEMBER 2019 TC 81