Water-Vapor Measurements of Low-Slope Roofing Materials.
Water-Vapor Measurements of Low-Slope Roofing Materials.
(1594 K)
Burch, D. M.; Desjarlais, A. O.
NISTIR 5681; 32 p. July 1995.
Available from:
National Technical Information Service
Order number: PB95-251617
Keywords:
moisture; moisture transfer; sorption isotherm; water
vapor permeability; water vapor transfer; moisture
property
Abstract:
New measurement methods recently developed at the
National Institute of Standards and Technology were used
to measure the sorption isotherm and permeability of
several low-slope roofing materials at a mean
temperature of 24 deg C (75 deg F). The materials
included: fiberboard, perlite board, exterior-grade
plywood, polyisocyanurate board insulation with
glass-matt facers, and glass-fiber board insulation with
a facer. For the sorption isotherm measurements, the
materials were placed in various ambient relative
humidities ranging from a dry to a saturated state. The
equilibrium moisture content plotted versus ambient
relative humidity at 24 deg C (75 deg F) gave the
sorption isotherm. Separate sorption isotherms were
obtained for specimens initially dry (adsorption
isotherm) and specimens initially saturated (desorption
isotherm). For the permeability measurements, a series
of cup measurements was performed, and the permeability
was plotted as a function of the mean relative humidity
across the specimen. The measurements revealed that the
moisture properties of building materials are often
significantly dependent on average relative humidity.
Standard measurement methods currently in use in the
United States do not adequately account for the effect
of relative humidity on moisture properties.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899