ASHRAE Journal - March 2010 - 40

Site Versus Source Energy A Backdrop to Energy Standards Development By Ronald E. Jarnagin, Member ASHRAE One major challenge to completing Standard 90.1-1999 was the controversy over the use of site versus source energy as the metric for determining energy savings. Stated simply, site energy is the energy actually delivered to the site of the building and metered by the respective utility meters. Source energy, on the other hand, represents the primary energy used to create the energy delivered to the site. Suppose that a building is heated with a natural gas furnace. In this case the natural gas used at the site of the building differs from the source energy at the wellhead by the pipeline transmission losses of a few percent, so that there is only a minor difference between site and source energy values. However, if the building is heated by electric resistance elements, then the site energy is the energy delivered to the site and measured by the building electric meter. Assuming the electricity was generated by natural gas in a combustion turbine, then the source energy (natural gas in this case) would be a much larger value than the site energy due to the inefficiencies associated with the conversion of thermal energy to electrical energy. (Source is more directly tied to greenhouse gas emissions and carbon reduction than site.) As one might expect from this example, the controversy is between the gas and electric utility industries. The electric utility industry would argue what is important to the building owner is metered electrical energy use at the site, while the gas utility industry would argue that source energy implications are more significant, and perhaps more correctly used in energy comparisons. Both positions represent valid but different perspectives on the implications of energy use. Regardless of the merits of the debate, it is true that both stakeholder groups wield considerable influence in standards-making processes such as ASHRAE, and both can be formidable opponents should they not agree with the direction of the project committee. This conflict of viewpoints has been around for decades and is not likely to change any time soon. It represents a continuing backdrop to the development of Standard 90.1. Historically, Standard 90.1 has been developed on a site basis because that translates into something the owner sees through utility meter readings. However, the 90.1 project committee has used energy costs for setting criteria for the 1999 standard, which tends to reflect the difference between site and source energy through differing fuel prices. The national average fuel prices used by the project committee for the 1999 standard were roughly equal to the national average site-source multipliers. Since gas and electricity compete with one another for heating applications, and to a much lesser extent for cooling applications, the controversy of site versus source energy is likely to continue. Unless and until the industry makes a transition to carbon as the metric for energy use the gas and electric utilities will likely continue their conflict over both approaches and solutions to energy savings in buildings. and Standard 90C-77 as a future standard 90.1 and a separate committee to update the residential provisions of Standard 90A-80 as a future standard 90.2. During the 80s the committees responsible for 90.1 and 90.2 continued their efforts with 90.1-1989 being published at the end of the decade and work to finish 90.2 continuing. Standard 90.1, published first in 1989, replaced Standard 90A-1980 and Standard 90B-1975. Based on work conducted in the early 80s under ASHRAE/DOE Special Project 41, research was conducted to demonstrate the cost effective changes possible in Standard 90. One significant change in Standard 90.1-1989 was the introduction of a building energy cost method for compliance that addressed some of the issues associated with prior performance approaches based only on energy use. In the prescriptive provisions of the standard, new criteria were added for transformer and electric motor efficiency. 1983 Newly formed project committee launches a two-step program to upgrade 90-75 and achieve the first part of a new two-part Standard 90 covering 90.1 (commercial) and 90.2 (residential). Electric power for lighting and lighting control provisions were tightened up and simplified, the building thermal envelope provisions were enhanced to more effectively address heat transfer, solar gains, internal gain variations and daylighting. Mechanical and service water heating equipment efficiencies were increased and systems provisions such as economizers enhanced. Estimates on a national level by DOE indicated that commercial building energy savings were around of 14% when comparing the provisions of Standard 90.1-1989 to 90-75. In parallel, continued adoption of updated energy standards and codes based on those standards occurred. By the end of the 80s, most states with authority to adopt such standards and codes had done so and were beginning to focus their efforts on implementation, enforcement and compliance. This set the stage for the adoption and implementation of further revisions to the standard. David R. Conover is a senior technical advisor for the Pacific Northwest National Laboratory in Washington, D.C. He 1989 1992 ASHRAE Special Project 41 provides research results for modifying the HVAC systems portion of the standard. Standard 90.1-1989: Major changes to performance criteria for building envelopes and lighting. Energy Policy Act made the formerly voluntary ASHRAE building standards mandatory. ASHRAE Journal ashrae.org March 2010

ASHRAE Journal - March 2010

Table of Contents for the Digital Edition of ASHRAE Journal - March 2010