Vapor Retarder

Vapor retarders can be an important moisture-control component of properly designed roof assemblies, helping reduce the transmission of water vapor and subsequent damage from condensation. Generally, vapor retarders are advisable as follows:

1. over heated buildings in regions where January temperatures average 40°F (4°C) or below,
2. over structures with high interior relative humidity, or
3. in any similar situation where a vapor drive can be expected. Improperly specified or constructed vapor retarders can have a deleterious effect on membrane performance.