ASHRAE has provided minimum standards for energy efficiency in building construction since the publication of Standard 90 in 1975. This presentation will provide a detailed review of the building envelope requirements for hot climates in the 2013 version of ASHRAE/IES Standard 90.1, and highlight changes from the previous criteria for hot climates in the 2010 version of ASHRAE/IES Standard 90.1. This paper will inform attendees about changes in energy standards, thereby providing consulting engineers, building owners, governmental representatives, and others with information to update their design practices and national codes and standards to incorporate improvements in the energy efficiency of the building envelope.

As an overview, approximately two-thirds of the criteria in the prescriptive compliance tables have changed. For hot climates, these changes will reduce cooling loads while still considering the benefits of daylighting. For roofs, thicker insulation is required, which will reduce heat gain during peak hours of overhead sun. For windows, lower U-factors are required, which will reduce heat gain due to conduction during occupied hours when outside air temperatures are hot and the internal loads are high. Low solar heat gain coefficient (SHGC) is required. But, now a minimum visible transmittance (VT) to SHGC ratio is established to ensure that windows provide adequate daylight even when they are reducing solar gain. The paper provides details on these and other changes in building envelope criteria.

Energy efficiency is a key component of ASHRAE's goals to minimize the environmental impact of building construction and operation. This paper provides the information needed for consulting engineers and others to keep their designs up with the latest energy efficiency standards for building construction.