Building Energy Codes

STATE OF CALIFORNIA TITLE 24

California Code of Regulations (CCR) building energy code prescribes a cool roof for many low slope, non-residential applications.

Title 24 incorporates both solar reflectance and thermal emittance measures into its cool roofing standard.  Under this building energy code, a roofing material’s aged thermal emittance must be .75 or greater and aged solar reflectance must be .55 or greater to be in compliance with the legislation. For new products, a calculation is available to estimate the projected aged value. Enforcement occurs according to climate zones, and a solar reflective index (SRI) of 64 is an alternative to meeting separate solar reflectance and emittance requirements.

Effective January 2014, Title 24 amendments will go into effect, including changes to the aged reflectance and SRI values for new construction and reroofs, with additional options for tradeoffs. Stay on top of developments at www.energy.ca.gov/title24.

Cool roofs are required on low-slope buildings when the owner or developer is using the prescriptive envelope component method for meeting Title 24 requirements. It is the simplest, most cost-effective way to comply with the standard in commercial re-roofing projects. Review the cool roofing codes and regulations here:

Envelope Component Approach
Complexity Simplest
Flexibility Least flexible
Tradeoffs Does not allow tradeoffs – each building component must meet or exceed the requirement for that climate zone
Calculations Fewest calculations
Cool roof requirement Cool roof is required for low-sloped and steep sloped buildings
Overall Envelope TDV Energy Approach
Complexity More complex
Flexibility Somewhat flexible
Tradeoffs Allows tradeoffs – if one building component does not meet the requirement but another exceeds it, it may offset the component that does not meet the requirement
Calculations Requires more calculations
Cool roof requirement Cool roof is not necessarily required
Whole Building Performance Approach
Complexity Most complex
Flexibility Most flexible
Tradeoffs Allows tradeoffs – if one building component does not meet the requirement but another exceeds it, it may offset the component that does not meet the requirement
Calculations Requires computer simulations
Cool roof requirement Cool roof is not necessarily required

U.S. GOVERNMENT

Federal Acquisition Regulation Case 1999-011 (formerly Executive Order #13123) required federal office buildings (Department of Defense, General Services Administration and National Aeronautics and Space Administration) to reduce energy consumption 30 percent by 2005, and 35 percent by 2010; federal industrial labs 20 percent by 2005 and 25 percent by 2010. ENERGY STAR products must be used when available.

Under President Obama’s Executive Order on Sustainability, issued October 2009, the federal government is required to reduce its greenhouse gas emissions 28 percent by 2020.

As part of this initiative, on June 1, 2010, former Energy Secretary Steven Chu announced that all Department of Energy offices would be required to select cool roofs when undergoing roof construction projects or replacing old ones, unless deemed uneconomical by a life-cycle cost analysis.

Chu’s memo (complete download available here PDF icon  [396 KB] provides the following guidance for determining a cool roof:

To be considered cool, a low-sloped roof (pitch less than or equal to 2:12) must be designed and installed with a minimum 3-year aged solar reflectance of 0.55 and a minimum 3-year aged thermal emittance of .75 in accordance with the Cool Roof Rating Council program, or with a minimum 3-year aged solar reflectance index (SRI) of 64 in accordance with ASTM Standard E1980-01.

To further shed light on cool roofing for federal and commercial building operators planning on installing cool roofs, DOE released its Guidelines for Selecting Cool Roofs PDF icon  [804 KB], which provides technical details on types of roofing materials and how to select the roof that will work best on a specific facility.