Water that gains access to the roof insulation
LITERATURE CITED
of a freezer at flaws in the waterproofing sys-
tem, and moist air that gains access at air gaps
ASTM (1990) C1153-90 standard practice for the
at the perimeter and at penetrations, freezes in
location of wet insulation in roofing systems us-
place. This ice adversely affects the insulating
ing infrared imaging, American Society for Test-
ability of the roof. Ice conducts heat about four
ing and Materials, West Conshohocken, Penn.
times as fast as water, so the loss in insulating
Tobiasson, W., and A. Greatorex (1994) Use of an
ability is quite dramatic for freezers where much
infrared scanner and a nuclear meter to find wet
of the moisture in their roofs is in the form
insulation in a ballasted roof. Proceedings,
of ice.
Thermosense XVI, Society of Photo-Optical Instru-
Ice that accumulates in the roof insulation of a
mentation Engineers, Bellingham, Wash. Also
freezer acts as a dam, allowing additional mois-
available as CRREL Misc. Paper MP 3422.
ture to accumulate above as ice or, in the upper,
Tobiasson, W ., and C. Korhonen (1985) Roof
warmer portions of the roof, as water. Seasonal
moisture surveys: Yesterday, today and tomorrow.
variations in outdoor temperatures do not pro-
Proceedings, Second International Conference on Roof-
mote drying of this moisture. The year-round ten-
ing Technology, National Roofing Contractors As-
dency is to promote wetting. Thus, there is incen-
sociation, Rosemont, Ill. Also available as CRREL
tive to use a very moisture-resistant insulation
Misc. Paper MP 2040.
in the roofs of freezers and, for the same
Tobiasson, W., A. Greatorex, and D. Van Pelt
reason but to a lesser degree, in the roofs of
(1991) New wetting curves for common roof in-
coolers. The two most moisture-resistant roof in-
sulations. Proceedings, 1991 International Symposium
sulations are cellular glass and extruded polysty-
on Roofing Technology, National Roofing Contrac-
rene. However, since cellular glass insulation can
tors Association, Rosemont, Ill. Also available as
be destroyed in short order by freeze-thaw
CRREL Misc. Paper MP 2866.
cycles in the presence of moisture (Tobiasson et
Tobiasson, W., B. Young, and A. Greatorex (1997)
al. 1997), the only currently available roof insula-
Freeze-thaw durability of common roof insula-
tion that can offer much improved moisture resis-
tions. Proceedings, Fourth International Symposium
tance in the roofs of freezers and coolers is ex-
on Roofing Technology, National Roofing Contrac-
truded polystyrene.
tors Association, Rosemont, Ill.
36
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