March 30 , 2006
The Hygrothermal Performance of Exterior Wall Systems: Key Points of the Oak Ridge
National Laboratory NET Facilities Research Project.
Study Goals:
1. Validate the moisture and air leakage control and thermal performance of EIFS wall systems.
2. To demonstrate the superior performance of EIFS over other types of exterior claddings.
3. To develop and calibrate a hygrothermal (moisture and temperature) computer model with
the unique features of EIFS that will validate the computer model for all climatic regions.
Results and Conclusions: 1. The best performing wall system was the EIFS wall consisting of four inches of expanded polystyrene insulated board without any interior stud insulation (no fiberglass). This wall outpeformed all other walls in moisture while maintaining superior thermal performance.
2. The brick wall systems tended to accumulate more moisture and retain moisture longer than
other types of exterior cladding.
3. The wall panels with polyethylene vapor retarders have higher wood moisture content and excessive interior insulation relative humidity (80% or higher). The results from this study clearly indicate that the use of polyethylene vapor retarder is not a good strategy.
