February 24, 2017
By Wanda Edwards, PE, RCI Senior Director of Technical Services
The 2016 edition of the energy-saving standard, ANSI/ASHRAE/IES Standard 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings, is now available for purchase.
One of the most notable changes is a result of analyses of more recent weather data, which resulted in the creation of the new Climate Zone 0, as well as changes within each climate zone in the United States. Climate Zone 0 has no effect on the U.S.; however, there are 400 counties in the U.S. that have been assigned to warmer climate zones than in the previous version of 90.1, resulting in less stringent requirements and creating less energy-efficient buildings. These changes demonstrate that the effects of climate change and global warming have an impact on the climate map.
As was noted by a speaker I recently heard, we base our maps on historical data. With the changes occurring to our climate, our maps are probably obsolete by the time they are published. The speaker observed that we need to look to the future and base energy conservation standards on the predicted climate changes, not what has happened in the past. RCI monitors the work of the ASHRAE Building Envelope Subcommittee. Its chairman, Len Sciarra, notes:
The envelope section has four major areas of improvement. The mandatory provisions now include the addition of an envelope verification in support of reduced air infiltration and increased requirements for air leakage of overhead coiling doors. The prescriptive requirements include increased stringency requirements for metal building roofs and walls, fenestration, and opaque doors. Requirements for Climate Zone 0 have been added for all assemblies, and there is improved clarity of the standard in defining exterior walls to building orientation to clarify default assumptions for the effective R-value of air spaces and calculation procedures for insulating metal building walls.”1
In the past, 90.1 has provided two compliance paths: a prescriptive path and a performance path. The performance path is a simulation method called the Energy Cost Budget (ECB) Method. The new compliance path is also a simulation method and can be found in Appendix G. In the past, this Appendix was used to demonstrate compliance for more stringent standards such as the International Code Council’s International Green Construction Code, and USGBC’s LEED rating system, but it can now be used to demonstrate compliance with the 90.1 requirements. Appendix G allows credit for some design elements that are not addressed in the ECB Method, such as building orientation, efficient use of building thermal mass, and properly sized HVAC equipment. As explained by Michael Rosenberg with Pacific Northwest National Laboratory (PNNL):
The second impactful change is that baseline design is now fixed at a stable level of performance set approximately equal to 90.1-2004. The stringency of the baseline is not meant to change with subsequent versions of the standard. Instead, compliance with new versions of the standard will simply require a reduced Performance Cost Index (PCI). A PCI of one is equal to the 2004 baseline, and a PCI of zero is a net-zero energy-cost building. Using this approach, buildings of any era can be rated using the same method. The intent is that any building energy code or beyond code program can use this methodology and merely set the appropriate PCI target for their needs.”2
The PNNL estimates that overall energy savings with the new standard are 4.2% with energy cost savings of 4.8% over the 2013 edition of the standard. Copies of the new edition, as well as more detailed information on the changes, are available at www.ashrae.org.
- “A Conversation on Standard 90.1-2016.” ASHRAE Journal, December 2016.