The 2013 CA Energy Code – Will Higher Reflectance Requirements Cause Condensation?
Phil Dregger
Format: MP3 Audio file download

As January 1, 2014 prescriptive requirements for aged solar reflectance for low-sloped roofs in California increased from 0.55 to 0.63. Will the higher values cause condensation? (Note: The higher values apply to all of California which includes ASHRAE Climate Zones 2 thru 6.). This presentation will explain how old "hot" roofs helped control roof condensation (moisture accumulation) and how switching to highly reflective "cool" roofs can sometimes cause a moisture problem. The focus will be on examples where wood decks, with insulation below, had been accumulating relatively large amounts of moisture for years but old non-cool built up roofs had helped them avoid problems by heating up and facilitating drying every time the sun came out. In such cases, installation of highly reflective cool roofs can inadvertently disrupt the balance between seasonal wetting and drying – causing increased moisture accumulation, condensation, and mold growth.

Learning Objectives:

• Why wood decks with insulation installed below tend to accumulate more moisture than wood decks with insulation installed above.
• The overwhelming influence of air intrusion on moisture accumulation in roofs.
• The importance of clarifying Building Code requirements for ventilating "enclosed rafter spaces" as part of low-sloped roofs.
• Three strategies to avoid condensation in roofs in "mild" climates over modestly humid environments.
• Selected aspects of the ANSI/ASHRAE Standard 160-2009 "Criteria for Moisture-Control Design Analysis in Buildings".
• How hygrothermal modeling can be used to illustrate the net "wetting" impact of lowering roof membrane temperatures.

Target Audience:

• Commercial Contractor
• Architect/Designer/Consultant
• Manufacturer-Supplier
• Owner/CEO/General Manager
• Building Owner/Facility Manager