26 September 2006
in the roof system greatly affects the performance of the roof system. Insulation system
shall be selected and designed to meet the mechanical system's design and energy
requirements of the facility.
Types of Roof Insulation.
Cellular Glass Insulation. Cellular glass roof insulation is not widely
used due to its high cost. It is most commonly used in cold storage facilities and other
areas where excessive amounts of moisture would degrade the insulating capabilities of
other types of insulation.
Perlite Board Insulation. Perlite board insulation is commonly used and
may be specified where factors other than insulating efficiency per unit thickness are the
primary design considerations. It is particularly useful in roof assemblies where fire
resistance is of primary concern and the potential for water vapor intrusion is limited.
Polyisocyanurate Foam Board Insulation. Polyisocyanurate foam
board is the most commonly used roof insulation. It is often specified where insulating
ability is the primary design consideration. However, it is frequently necessary to use
perlite or wood fiberboard in the roofing assembly to protect the polyisocyanurate from
physical damage, to improve fire resistance, or to provide a suitable surface for
adherence of the roof membrane.
Polystyrene Board Insulation. Polystyrene board roof insulation is used
by the military and is made in two types: molded expanded board (EPS) and extruded
expanded board (XPS). In terms of moisture resistance and insulating capability, XPS
is superior to EPS. It is also more expensive but appropriate for use in inverted
membrane systems and cold storage facilities. Do not use polystyrene in direct contact
with hot mopped systems. For the same reasons as with polyisocyanurate insulation, it
is frequently necessary to use perlite or wood fiberboard to meet other design
requirements in the roof assembly. When polystyrene is used on the interior of a
building it must be encased with a fire resistive material.
Wood Fiberboard Insulation. Wood fiberboard roof insulation has been
commonly used in military roof systems and may be specified where factors other than
insulating efficiency per unit thickness is the primary design consideration. It most
commonly used as the top layer of insulated roof assemblies where the roof membrane
will be adhered to the wood fiberboard. Wood fiberboard is more stable in assemblies
where moisture is limited.
Composite Board Insulation. Composite board roof insulation may be
specified where a multiple layer type of insulation does not satisfy all design
requirements, and where there are cost savings available from reducing the number of
construction operations needed to install two different kinds of roof insulation. Single
layer applications should be limited when possible.
Phenolic Foam Board Insulation. Phenolic foam board insulation
causes severe corrosion when in contact with steel roof decks. It is no longer