26 September 2006
Degree-Days. The sum of the positive or negative differences between a reference
temperature (usually 18C (65F)) and the mean temperature for each day in the
heating or cooling season). Degree-days are used to compare the severity of cold or
heat during the heating or cooling season
Delamination. Separation of the plies in a membrane or separation of insulation layers
Design loads. The "live load" and "environmental load" (i.e. superimposed loads) that
a structure is designed to resist (with appropriate safety factor) plus "dead load" (i.e.,
weight of permanent loads).
Dew point. The temperature at which water vapor starts to condense in cooling air at
the existing atmospheric pressure and vapor content.
A material that contains
no more water than one would find
at its equilibrium
Eave. The line along the sidewall formed by the intersection of the planes of the roof
Eave Height. The vertical dimension from finished floor to the eave.
Edge venting. The practice of providing regularly spaced protected openings at a low-
slope roof perimeter to relieve water vapor pressure in the insulation. (It is of doubtful
it regains its original size and
shape after removal of stress.
Elastomer. A macromolecular material that returns rapidly to its approximate initial
dimensions and shape after subsequent release of stress.
Embedment. (1) the process of pressing a felt, aggregate, fabric, mat, or panel
uniformly and completely into hot bitumen or adhesive to ensure intimate contact at all
points; (2) the process of pressing granules into coating in the manufacture of factory
prepared roofing, such as shingles.
of fine particles
of a liquid
in a liquid. Asphalt
emulsions consist of asphalt globules, an emulsifying agent such as bentonite clay and
Endlap. The overlap where one panel or felt nests on top of the end of the underlying
panel or felt.
EPDM. A synthetic elastomer based on ethylene, propylene, and a small amount of a
non-conjugated diene to provide sites for vulcanization. EPDM features excellent heat,
ozone and weathering resistance, and low temperature flexibility.