Revisions to Standard 90.1 Could Achieve More Energy-efficient Buildings

The requirements of the 2013 revision of an energy standard recently published by ASHRAE and IES will result in buildings that could achieve 6 to 8 percent more efficiency than buildings built to the 2010 standard.

Published in October 2013, ANSI/ASHRAE/IES Standard 90.1-2013, Energy Standard for Buildings Except Low-Rise Residential Buildings, provides minimum requirements for the energy-efficient design of buildings except low-rise residential buildings.

Pacific Northwest National Laboratories (PNNL), in support of the Department of Energy’s Building Energy Codes Program, conducted the energy savings analysis on 110 addenda included in the standard.

PNNL’s analysis shows that the site and energy cost savings are 37.7 percent and 37.8 percent, respectively, by using the 2004 standard as baseline for the regulated loads only. For the whole building energy consumptions, national aggregated site energy savings a­re 29.5 percent and energy cost savings are 29.0 percent.

On a nationally aggregated level, building-type energy savings range from 19.3 percent to 51.9 percent and energy-cost savings from 18.6 to 50.6 percent. These figures include energy use and cost from the whole building energy consumptions including plug and process loads.

“ASHRAE is committed to continually improving building energy performance, so we are pleased with this confirmation that the 2013 standard achieves significant energy savings over its predecessor,” William Bahnfleth, ASHRAE president, said. “As we approach the 40th anniversary of the publication of the standard, these new savings underscore Standard 90.1’s key role in promoting energy efficiency in buildings in the United States by establishing successively more stringent – but cost effective – minimum requirements and we look forward to further advances in future revisions.”

“The Illuminating Engineering Society of North America (IES) has provided technical support on lighting related requirements in each iteration of the standard since 1975,” Rita Harrold, director of technology, said. “IES continued that role in developing the energy efficiency provisions in the 2013 standard through modified LPDs and additional daylighting and controls strategies. The challenge to achieve higher energy efficiencies increases with each version of the standard and begins anew as we address targets for the 2016 edition.”

Extensive analysis work was performed by a team from Pacific Northwest National Laboratories. Sixteen different building prototypes were modeled in 17 different climate locations for a total of 272 building types and climate zone combinations

The energy reduction was achieved through 33 addenda related to major changes to requirements regarding building envelope, lighting, mechanical and the energy cost budget. The most significant changes are:

    Building Envelope. Opaque elements and fenestration requirements have been revised to increase stringency while maintaining a reasonable level of cost-effectiveness. Opaque and fenestration assemblies in Tables 5.5-1 through 5.5-8 are revised in most climates. These changes include:

  • Criteria requiring double glazed fenestration in many climates
    Minimum visible transmittance/solar heat gain coefficient (VT/SHGC) ratio to enable good daylighting with minimum solar gain, while not restricting triple- and quadruple-glazing.
    Simplification of the skylighting criteria.
  • Lighting: These changes include improvements to daylighting and daylighting controls, space-by-space lighting power density limits, thresholds for toplighting and revised controls requirements and format.
    Mechanical: Equipment efficiencies are increased for heat pumps, packaged terminal air conditioners, single package vertical heat pumps, air conditioners and evaporative condensers. Also, fan efficiency requirements are introduced for the first time. Additional provisions address commercial refrigeration equipment, improved controls on heat rejection and boiler equipment, requirements for expanded use of energy recovery, small motor efficiencies and fan power control and credits. Control revision requirements have been added to the standard such as direct digital controls in many applications.

Another important change for the 2013 standard is the first alternate compliance path in Chapter 6. Section 6.6 was added to the 2010 edition to provide a location for alternate methods of compliance with the standard. The first such alternate path has been developed for computer room systems and was formulated with the assistance of ASHRAE technical committee 9.9, Mission Critical Facilities, Data Centers, Technology Spaces and Electronic Equipment. This path uses the Power Usage Effectiveness (PUE) metric established by the datacom industry. This alternate efficiency path format provides a framework that could be considered for other energy using facets of buildings not easily covered in the prescriptive provisions of the standard.

The standard is written in mandatory code language and offers code bodies the opportunity to make a significant improvement in the energy efficiency of new buildings, additions and major renovations.

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