There are a number of factors that are very important to the installer and building owner but are not part of the specifications.
Polyiso vs xps attic.
In this video dow chemical rep kevin and i will tell you about the differences between.
Some of the key attributes are shown here.
Polyiso is classified as a thermoset material.
Xps is classified as a thermoplastic material.
For mineral fiber board r values vary between supplier but are around r 4 0 inch significantly less than for polyiso.
Extruded polystyrene xps is somewhat lower than polyiso.
A thermosoftening plastic or thermoplastic is a polymer that softens or turns to a liquid when heated.
Polyiso is a thermoset material meaning it is permanently rigid and cannot be melted back to liquid form.
A thermosetting plastic also known as thermoset is a polymer material that irreversibly cures.
Thermoset materials are generally stronger that thermoplastic due to the network of bonds and are better suited for high temperature applications.
I think there are two good choices for exterior rigid foam insulation.
We always choose and recommend eps over xps due to the fact that xps has much higher greenhouse gas emissions than eps.
Xps is a thermoplastic material which softens or turns to a liquid when heated.
Xps is degraded by uv light but the facers on polyiso insulation protect the core from such damage.
Polyiso is compatible with a large number of roof and wall systems too.