There are four basic functions of the building envelope; adding structural support, controlling moisture and humidity, regulating temperature, and controlling air pressure changes.
Water in vapor or liquid form is a destructive force, which can deteriorate building components and cause extensive damage if not managed properly. Even when buildings are designed correctly, problems can occur if the installation of components is not monitored closely during construction. These problems can contribute to energy loss, structural damage, and the promotion of mold, leading to poor indoor air quality (IAQ).
The envelope commissioning process starts with a review of the initial envelope design, paying particular attention to material selection and details of their assembly. During construction, the building envelope commissioning consultant (BECC) monitors the installation of the various roof, wall and glazing components. Many envelope problems occur due to unwanted penetrations in the air and vapor barriers, improper installation of roof, wall and window flashings and incomplete coverage of waterproofing systems.
In addition to visual observations during construction, the BECC also develops a series of acceptance tests, verifying the tightness and thermal integrity of the envelope, along with its ability to withstand air leakage and moisture penetration.
Two generally accepted standards for building envelope commissioning are the NIBS Guideline 3-2012 – Building Enclosure Commissioning Process BECx, and ASTM E2813, Standard Practice for Building Enclosure Commissioning.
In addition, there are related standards dealing with envelope testing, including:
• ASTM E1827 – 11 Standard Test Methods for Determining Airtightness of Buildings Using an Orifice Blower Door
• ASTM E779 Test Method for Determining Air Leakage Rate by Fan Pressurization
• ASTM E783-02 Standard Test Method for Field Measurement of Air Leakage Through Installed Exterior Windows and Doors
• ASTM E1105-00 Standard Test Method for Field Determination of Water Penetration of Installed Exterior Windows, Skylights, Doors, and Curtain
Walls by Uniform or Cyclic Static Air Pressure Difference
Testing for air leakage and water penetration can include various procedures, including: thermal imaging, pressurizing (and de-pressurizing) spaces (or test chambers), and the use of a hose or spray rack to test for moisture tightness. The BECC develops the test protocols, directs the Contractor in preparing the test areas; then witnesses and documents the tests.
For additional information regarding building envelope commissioning, please contact RKnoedler@hanson-inc.com.