Moisture effects in low-slope roofs: Drying rates after water addition with various vapor retarders

Technical Report · Thu Oct 01 04:00:00 EDT 1992

DOI:https://doi.org/10.2172/6975843· OSTI ID:6975843

Pedersen, C. R. ^[1]; Petrie, T. W. ^[2]; Courville, G. E.; Desjarlais, A. O.; Childs, P. W.; Wilkes, K. E. ^[3]

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1. Technical Univ. of Denmark, Lyngby (Denmark)
2. Marquette Univ., Milwaukee, WI (United States). Dept. of Mechanical Engineering
3. Oak Ridge National Lab., TN (United States)

Tests have been conducted in the Large Scale Climate Simulator (LSCS) of the US. Building Envelope Research Center at the Oak Ridge National Laboratory (ORNL) to investigate downward drying rates of various unvented, low-slope roof systems. A secondary objective was to study heat flow patterns so as to understand how to control latent heat effects on impermeable heat flux transducers. Nine test sections were tested simultaneously. The sections had a p deck above fibrous-glass insulation and were examples of cold-deck systems. These five sections had various vapor retarder systems on a gypsum board ceiling below the insulation. The other four sections had a lightweight insulating concrete deck below expanded polystyrene insulation and the same vapor retarder systems, and were examples of warm-deck systems. The cold-deck systems had materials that were relatively permeable to water vapor, while the materials in the warm-deck systems were less permeable. All test sections were topped by an impermeable roofing membrane. The test sections were instrumented with thermocouples between all layers and with small heat flux transducers at the bottom and top of the fibrous-glass insulation and in the middle of the expanded polystyrene insulation. Two different kinds of moisture probes were used to qualitatively monitor the movement of the moisture. The heat flux measurements showed that heat conduction dominates the system using impermeable insulation materials, with only a slight increase due to increased thermal conductivity of wet expanded polystyrene. There was significant transfer of latent heat in the test sections with permeable insulation, causing the peak heat fluxes to increase by as much as a factor of two. With temperatures imposed that are typical of summer days, latent heat transfer associated with condensation and evaporation of moisture in the test sections was measured to be as important as the heat transfer by conduction.

• Research Organization: Oak Ridge National Lab., TN (United States)
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6975843
• Report Number(s): ORNL/CON-308; ON: DE93003591
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
320107* -- Energy Conservation
Consumption
& Utilization-- Building Systems-- (1987-)
42 ENGINEERING
420500 -- Engineering-- Materials Testing
ANALOG SYSTEMS
BUILDING MATERIALS
BUILDINGS
DRYING
FUNCTIONAL MODELS
HEAT FLUX
MAINTENANCE
MATERIALS
MATERIALS TESTING
MEASURING INSTRUMENTS
MOISTURE
ORGANIC COMPOUNDS
ORGANIC POLYMERS
PAPER
PETROCHEMICALS
PETROLEUM PRODUCTS
PLASTICS
POLYETHYLENES
POLYMERS
POLYOLEFINS
POLYSTYRENE
POLYVINYLS
ROOFS
SIMULATORS
SYNTHETIC MATERIALS
TESTING
THERMAL INSULATION
THERMOCOUPLES
WEIGHT