Requiring High Performance Windows in California

Charles Eley, Eley Associates
Bill Pennington, California Energy Commission

Keywords

Abstract

This paper describes the methods used to update the nonresidential fenestration requirements for the 2001 California Energy Efficiency Standards for Nonresidential and High-Rise Residential Buildings (standards). Before the 2001 changes, the standards allowed metal frames with single tinted glass along the coast and double tinted glass inland. With the changes, high performance fenestration is required by the prescriptive standards throughout California. The changes were implemented through an emergency rulemaking mandated by Assembly Bill 970 (Statutes of 2000).

California law requires that the standards be cost effective when amortized over the building life. A rigorous life-cycle cost procedure considered the cost of modern fenestration technologies, associated energy savings, views, and typical glass area in buildings. The procedure is summarized below:

Identify the candidate fenestration products that may be used in vertical and horizontal applications, and collect data on their performance characteristics and cost.
Develop an energy model that assesses the relative performance of candidate fenestration products and accounts for building type, orientation, and differences in U-factor, solar heat gain coefficient (SHGC), and visible light transmission (VLT).
Develop a subset of fenestration products intended for reducing U-factor.
Calculate the life-cycle cost of each U-factor subset. Set the U-factor criteria based on this analysis.
Establish conditions that would warrant setting different SHGC criteria levels (i.e., climate zone, building type, orientation, and fenestration area).
For each SHGC condition, calculate the life-cycle cost of each fenestration product in the full set. The product with the lowest life-cycle cost determines the SHGC criteria.
Review the criteria that results from the above steps and apply professional judgment to provide consistency among similar climates and fenestration area ranges.