Vapor Barrier Facings
In addition to acting as a decorative protection barrier, facings serve an integral part of the overall insulation system. Facings provide vapor barriers, light reflectivity and structural strength. In most cases, a reinforcement of fiberglass or polyester scrim is used for extra rigidity and greater impact resistance.
Facings As Vapor Barriers
The main function of facings is to act as a vapor barrier. While a vapor barrier may not necessarily be able to stop the flow of water vapor, it does an excellent job of minimizing the rate and volume of the flow. This prevents moisture from accumulating within the insulation blanket and the structure which translates into consistent thermal values and lower heating and cooling costs.
The effectiveness of a vapor barrier depends on three primary factors:
- Location within the insulated section
- Permeance
- Proper installation
Facings intended to serve as vapor barriers should be installed on the inner, heated surface of the insulation, where vapor pressure is the highest. This helps in preventing vapor from reaching the cooler air and condensing.
WARNING! With standard vinyl, cold temperatures can cause cold crack, a situation where the facing becomes brittle and if handled can crack.
Perm Rating
The perm rating, or permeance, is a measure of the amount of water that passes through one square foot of material per hour. The lower the perm rating in a vapor barrier material, the more effective the barrier becomes.
A facing material with a perm rating of 0.1 or less is considered excellent. Anything with a rating above 1.0 is not considered a vapor barrier.
Installation and Selection
Proper installation and selection is imperative for maximum effectiveness. Please refer to installation instructions to ensure correct procedures are used. Facings that have been torn or punctured are no longer capable of blocking water vapor and may eventually do more harm than good. Be sure to quickly patch any holes in the vapor barrier.
When selecting a facing, special consideration should be given to its reflective quality. A facing with high reflectivity reduces the need for high lighting levels in work areas. This results in reduced energy costs and increased productivity.