INSULATION REQUIREMENTS can be tricky depending on which code your
project has to meet. IECC 2018 and ASHRAE 90.1-2016 have different approaches
to minimum required R-values.
are directly above a cooled space, so
any areas that are heating-only don’t
have to comply.
ASHRAE also requires cool roofs for
buildings with slopes under 2: 12, but
makes exemptions for semi-heated
spaces, conditioned spaces that aren’t
cooled, and metal buildings and asphaltic membranes located in climate zones
0 or 1. With 90.1, you’re required to use
material with a thermal reflectance of
0.55 and thermal emittance of 0.75, or
alternatively, a product with a three-year
aged SRI of 64.
Also note that if you need a non-cool
color for corporate branding or other
reasons, you can get around these
requirements by providing extra insula-
For example, zones 2 and 3 have to
provide R- 20 to 25, but if you’re choosing the trade-off option you need to provide R- 33 instead.
Both codes provide specific instruc-
tions for re-roofing projects, and in some
cases even exempt
them from having to
meet the newest code
as long as the energy
use of the building is
“If you’re doing a re-
cover or anything less
than a full replacement,
in most cases you’re
not going to have to
meet the new energy
code,” Wilen says.
“However, if you’re tak-
ing your roofing system
all the way down to
the structural deck and
starting over, you’re probably going to
have to meet the new requirements.”
Janelle Penny janelle.penny@buildings.
com is Senior Editor of BUILDINGS.
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"If you’re doing a re-cover or anything
less than a full replacement, in most cases
you’re not going to have to meet the new
energy code. However, if you’re taking your
roofing system all the way down to the
structural deck and starting over, you’re
probably going to have to meet the new
– Jason P. Wilen, Director of Technical Services,
National Roofing Contractors Association