Updated ASHRAE/IES energy standard gains 30% savings

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

The 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.

Analysis from Pacific Northwest National Laboratories (PNNL) shows that the site and energy cost savings are 37.7 to 37.8%, 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% and energy cost savings are 29%.

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

Extensive analysis work was performed by a team from PNNL. Sixteen different building prototypes were modelled 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 alternative 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.