Moisture Control in Low-Slope Roofing: A New Design Requirement

A.O. Desjarlais and J.E. Christian, Oak Ridge National Laboratory
N. A. Byars, University of North Carolina Charlotte




Moisture Control Strategies Presently Employed

Proposed Moisture Control Strategy

Developing the Algorithms

Using the Algorithms

An Example

Comparison with Existing Methods

Conclusions/Future Work




Algorithms have been proposed that can be used by the roofing designer to assess the moisture tolerance of a roofing system. Given the location and indoor conditions of the building, the designer can use these algorithms to determine if a vapor retarder is needed, if small leaks in the roofing system will translate into leaks into the building, and the relative ability for the roofing system to be self-drying. He can vary roof membrane color, insulation type and thickness, and deck permeance until he optimizes these parameters (subject to other limitations) from a moisture perspective. Experimenting with these algorithms will hopefully offer insight into the basics of moisture control.

Future Work

The algorithms proposed in this paper are presently limited to roof systems and environmental conditions detailed in Table 1. Future work will include the analysis of roofing systems with a wider range of properties in order to establish the limitations of the predictive algorithms. A wider variety of insulation types, decks, and indoor vapor pressures need to be evaluated to assess the accuracy of the proposed algorithms to roofing systems and components that are presently not in our database.

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Building Envelope Research
Oak Ridge National Laboratory

For more information, contact the program manager for Building Envelope Research:

André O. Desjarlais
Oak Ridge National Laboratory
P. O. Box 2008, MS 6070
Oak Ridge, TN 37831-6070

E-mail Andre Desjarlais

Revised: May 26, 2004 by Juanita Denton