26 September 2006
Tensile Test. A test in which a specimen is subjected to increasing longitudinal pulling
Therm. A unit of heat commonly used by utilities, equivalent to 100,000 BTU = 1.05 x
Thermal Conductivity (k).
of heat flow through
a stated thickness
with a stated temperature differential Btu/h.ft20F (W/m20C).
Thermal Insulation. A material designed to reduce the conductive heat flow.
Thermal Shock. Stress-producing phenomenon resulting from sudden temperature
drops in a roof membrane--when, for example, a rain shower follows brilliant sunshine.
Thermoplastic Elastomers. Polymers capable of remelt, but exhibiting elastomeric
properties; related to elasticized polyolefins. They have a limited upper temperature
U-Factor. The heat flow across an entire assembly e.g., from air within a building to
outside air; the inverse of R-Factor.
Uplift. Wind load on a building which causes a load in the upward direction.
Vapor Barrier. See Vapor retarder.
The pressure exerted
by a vapor that
is in equilibrium with its solid
Vapor Retarder. A material that resists the transmission of water vapor.
Vent. Opening designed to convey water vapor or other gas from inside a building or a
building component to the atmosphere.
Viscoelastic. Characterized by changing mechanical behavior, from nearly elastic at
low temperature to plastic, like a viscous fluid, at high temperature.
of a fluid's internal resistance
to flow, measures
in centistokes (cSt)
for bitumens. (Water has a viscosity of roughly 1 cSt, light cooking oil 100 cSt.)
Waterproofing. Treatment of a surface or structure to prevent the passage of water
under hydrostatic pressure.