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Abstract
Many roofs are replaced because water accumulates in portions of the roofing system. These accumulations can cause dripping, accelerated membrane failure, poor thermal performance, threat of structural decay, and depreciation of building assets. Traditionally, the roofing industry has been concerned with controlling the inflow of water into the roof. An example of this strategy would be the development of a more relilable membrane. However, roof membranes inevetiably leak. For this reason, the roof design strategy of the future must be concerned with controlling water outflow. Following are the requirements for this type of roof system. Under normal operating conditions (no leaks), the total moisture content of a self drying roof system shall not increase with time and condensation shall not occur under the membrane during winter uptake. Moisture vapor movement by convection must be eliminated and the flow of water by gravity through imperfections in the roof system must be controlled. After a leak has occurred, no condensation on the upper surface of the deck shall be tolerated and the water introduced by the leak must be dissipated to the building interior in a minimum amount of time. Finite-difference computer modeling is used to demonstrate the effectiveness of the design. The impact of deck and insulation permeance, climate, leaks and winter water uptake is simulated. A data base of simulations is qualitatively described; this data base will be used in future work to produce a simplified means of assessing the design parameters of a self-drying roof system.
Many roofs are replaced because water accumulates in portions of the roofing system. These accumulations can cause dripping, accelerated membrane failure, poor thermal performance, threat of structural decay, and depreciation of building assets. Traditionally, the roofing industry has been concerned with controlling the inflow of water into the roof. An example of this strategy would be the development of a more relilable membrane. However, roof membranes inevetiably leak. For this reason, the roof design strategy of the future must be concerned with controlling water outflow. Following are the requirements for this type of roof system. Under normal operating conditions (no leaks), the total moisture content of a self drying roof system shall not increase with time and condensation shall not occur under the membrane during winter uptake. Moisture vapor movement by convection must be eliminated and the flow of water by gravity through imperfections in the roof system must be controlled. After a leak has occurred, no condensation on the upper surface of the deck shall be tolerated and the water introduced by the leak must be dissipated to the building interior in a minimum amount of time. Finite-difference computer modeling is used to demonstrate the effectiveness of the design. The impact of deck and insulation permeance, climate, leaks and winter water uptake is simulated. A data base of simulations is qualitatively described; this data base will be used in future work to produce a simplified means of assessing the design parameters of a self-drying roof system.
Date
12/1995
12/1995
Author(s)
Andre Desjarlais
Andre Desjarlais
Page(s)
763-773
763-773
Keyword(s)
self drying roof; moisture; thermal performance; membrane failure; structural decay; leak;
self drying roof; moisture; thermal performance; membrane failure; structural decay; leak;