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Abstract
The roofinbg industry has traditionally held that moisture control in low slope roofing compromises two independent elements: 1) provide a waterproof exterior covering to protect the low slope roof from external soures of moisture; 2) perform a condensation calculation to determine if a vapor retarder is required to protect a roof system from internal moisture sources. The first criterion is assumed to be satisfied if a membrane system is specifed; in reality, all membrane systems eventually fail, and existing moisture control strategies offer no mechanism for analyzing the inevitable failure. The means of assessing the second criterion, has evolved in recent years. The criteria have become more liberal with time because it has been observed that roofing systems installed in a geographic area in which the old criteria required a vapor retarder, have performed well without one. The service life of a roofing system ends when it can no longer provide the necessary protection from the environment. All too often, moisture accumulation in the roofing system accelerates its demise. The effectiveness of the roofing industry's existing moisture control philosophy needs to be questioned. The average life of a roofing system is a fraction of the life of other building envelope components, and the primary reason for failure is water leakage. An improved moisture control strategy may very well be the key to iimproving the durability of low slope roofing. In this paper, the authors propose a new moisture control stratege that addresses not only condensation control, but also water leakage. They compare the new strategy with those predating it, describe the benefits of the new strategy, and illustrate by example the necessary inputs to implement it.
The roofinbg industry has traditionally held that moisture control in low slope roofing compromises two independent elements: 1) provide a waterproof exterior covering to protect the low slope roof from external soures of moisture; 2) perform a condensation calculation to determine if a vapor retarder is required to protect a roof system from internal moisture sources. The first criterion is assumed to be satisfied if a membrane system is specifed; in reality, all membrane systems eventually fail, and existing moisture control strategies offer no mechanism for analyzing the inevitable failure. The means of assessing the second criterion, has evolved in recent years. The criteria have become more liberal with time because it has been observed that roofing systems installed in a geographic area in which the old criteria required a vapor retarder, have performed well without one. The service life of a roofing system ends when it can no longer provide the necessary protection from the environment. All too often, moisture accumulation in the roofing system accelerates its demise. The effectiveness of the roofing industry's existing moisture control philosophy needs to be questioned. The average life of a roofing system is a fraction of the life of other building envelope components, and the primary reason for failure is water leakage. An improved moisture control strategy may very well be the key to iimproving the durability of low slope roofing. In this paper, the authors propose a new moisture control stratege that addresses not only condensation control, but also water leakage. They compare the new strategy with those predating it, describe the benefits of the new strategy, and illustrate by example the necessary inputs to implement it.
Date
10/1996
10/1996
Author(s)
Andre Desjarlais; Nan Byars
Andre Desjarlais; Nan Byars
Page(s)
47-61
47-61
Source
Oak Ridge National Lab
Oak Ridge National Lab
Keyword(s)
sustainable roofing; moisture design; durability; ORNL; low slope;
sustainable roofing; moisture design; durability; ORNL; low slope;