Section 3: THERMAL INSULATION
Purposes for Insulation. There are several purposes
for using roof insulation as follows:
Reduce heating and cooling equipment capacity.
Reduce heating and cooling energy use.
Provide smooth substrate for roofing membrane.
Provide slope to flat roof decks.
Design Factors. A number of physical properties and
application criteria must be considered in the design of each
roof. Evaluation of these factors should consider the entire
range of conditions that the roof assembly will be exposed to,
including the extremes.
Compressive Strength. Consider the likely extent of
roof traffic (including construction traffic) and insulation type
Moisture Absorption. Where roof insulation is used in
humidified buildings or in areas with large vapor pressure
differentials, it is likely that moisture will accumulate in the
insulation, even with the use of vapor retarders (refer to
Section 4). Moisture absorption reduces the thermal resistance
of insulation. When it is probable that moisture will accumulate
in the insulation, the types of insulation material to be
utilized should be those which are least likely to absorb
Temperature. Provisions for expansion should be
provided in order to accommodate changes in dimension due to
temperature. The temperature range should consider the annual
extremes. During colder weather, clear sky radiation can result
in roof temperatures lower than design temperatures. During
warmer weather, as a result of solar radiation, and depending
upon roof color, roof temperatures in excess of 150 degrees