Published: Jan 1980
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In the past, thermal effects of moisture and deteriorating effects of moisture on constructions were considered separately rather than as total potential problems that arise from interactions dictated by the laws of physical performance. This paper contributes thermal data on two large industrial buildings; on one the roof insulation had become flooded, on the other the insulation was essentially dry. Also presented are brief examples of adverse effects of moisture in walls and floors. To present only data on excessive heat flow from moisture without also indicating how common problems induced by moisture may arise would not be helpful to those not familiar with the laws of physical performance. Without such associated information, little will be accomplished in overcoming moisture problems through preventive design, construction, and maintenance.
Three times as much heat flowed through the roof with flooded insulation as through the roof on which the insulation remained dry. This ratio of three was also found in the same location when the wet insulation was replaced with dry. During hot days, 35°C (95°F), the reduced peak heat flow from wet to dry insulation to maintain 24°C (75°F) indoors was equivalent to 40 W/m2 [12.8 Btu/(ft2·h)] or about one ton of refrigeration per 92 m2 (1000 ft2).
Roofing granules that reflect sun heat were found to reduce heat-transfer rate into the building, but the indications were that reliable reflectance data on materials being considered for such use are necessary, because light color to the eyes does not necessarily indicate effective reflectance of solar heat.
thermal insulation, R, -value, moisture migration, moisture condensation, heat reflectance, heat flow rate
Consulting engineer, State College, Pa.