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The latest version of the important energy standard popularly known as ASHRAE 90.1 was recently published under joint sponsorship by ANSI (American National Standards Institute, http://www.ansi.org/), ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers, http://www.ashrae.org/) , and IESNA (Illuminating Engineering Society of North America, http://www.iesna.org/). This standard is generally regarded as the definitive source of guidelines for achieving energy efficiency, and many other codes and standards (such as the latest version of the International Energy Conservation Code or IECC, http://www.iccsafe.org/) either have or are expected to adopt the requirements published under ASHRAE 90.1.

The changes from the 1999 to the 2001 version are largely clarifications of language used in the 1999 version which some found confusing. For example, the 1999 version of section 9.2.1.1 (c) stated that one acceptable method of automatic lighting control was "by occupant intervention." The 2001 version of this section clarifies that compliance with this section requires "a signal from another control or alarm system that indicates the area is unoccupied."

The information presented below is intended to provide a overview of the most significant elements of ASHRAE 90.1 (related to lighting). The full text of this standard -- as well as recently adopted addenda to the published standard -- is available from ASHRAE.

The 2001 version builds upon the 1999 version of the ASHRAE standard and maintains many of its features including [PDF]:

• The requirement that states adopt a building code at least as stringent as ASHRAE 90.1-1999 by 7/15/2004 or justify why they cannot comply. This legislation -- the full title of which is the Building Energy Standards Program: Determination Regarding Energy Efficiency Improvements in the Energy Standard for Buildings, Except Low-Rise Residential Buildings -- is mandated by the U.S. Department of Energy (DOE) as an update to the Energy Policy Act (EPAct) of 1992. The full text of this legislation can be obtained in either text or PDF format using the following links:
• The primary application is new construction and major renovations of commercial, industrial and institutional structures. Low-rise residential structures are excluded.

The 1999/2001 version includes several key changes from the 1989 version:

• More stringent lighting power requirements and codes written in more enforceable language.
• Required use of lighting controls for many applications (details below).
• Control points for spaces are no longer used.
• Building area power allowances (W/ft2) no longer depend on the size of the buildings.
• Area factor, a function of ceiling height and floor area, is no longer calculated.
• Exterior lighting power requirements have been simplified. Specifically, most exterior lighting power requirements are now stated in terms of minimum efficacy (lumens/watt).

State Adoption of ASHRAE 90.1-1999
As shown in the map below, as of September, 2002, 18 states have adopted ASHRAE 90.1-1999, 15 have adopted ASHRAE 90.1-1989, and the remainder have adopted standards less stringent than ASHRAE 90.1-1989. As of July, no states had adopted the 2001 version but, as noted above, the requirements of the 2001 version are essentially the same as the 1999 version.

State adoption of ASHRAE 90.1 and other energy legislation changes continuously. For example, Michigan adopted ASHRAE 90.1-1999 in March, 2003.

A good reference for staying abreast of the current status of adoption by state -- and for finding out about compliance and training tools -- is the DOE's website on Building Energy Codes (http://www.energycodes.gov/). For the latest information on the status of state adoption please visit this site.

Interior Lighting Power
The 2001 version of ASHRAE 90.1 remains consistent with the requirements of the 1999 version regarding interior lighting power and allows some additional lighting power allowances to accommodate specific lighting needs. These include additional power for decorative lighting (1.0 watt per square foot), VDT terminal lighting (0.35 watts per square foot), and retail display lighting. In the latter case, either 1.6 watts per square foot of specific display area is allowed for general merchandise highlighting or 3.9 watts per square foot of specific display area is allowed for valuable merchandise highlighting. This additional power is only allowed if the specified luminaries are installed and can only be used for the specific purpose noted.

Three Methods For Calculating Interior Lighting Power
The ASHRAE standard provides three alternative methods of calculating the interior power requirements for a structure: (1) The building area method, (2) the space-by-space method, and (3) the energy cost method. For further details, select the link below.

http://www.cooperlighting.com/education/pdf/ASHRAEARTICLE.pdf

Building Area Method Lighting Power Densities
The maximum power densities allowed by ASHRAE 90.1 vary according to the type of space being illuminated and is measured in watts per square foot (W/ft2). For example, the maximum energy usage for some key types of spaces is as follows:

• Hospital - 1.6 W/ft2
• Library/School - 1.5 W/ft2
• Manufacturing - 2.2 W/ft2
• Museum - 1.6 W/ft2
• Office - 1.3 W/ft2
• Parking Garage - 0.3 W/ft2
• Retail - 1.9 W/ft2
• Gymnasiums - 1.7 W/ft2

Exit Signs
The 1999 version included an additional section specifying a minimum efficacy (35 lumens per watt) for all exit signs operating at greater than 20 watts, and the 2001 reaffirmed this requirement. This will essentially eliminate the use of incandescent lamp sources in exit signs.

Lighting Controls
The lighting controls requirements of both the 1999 and 2001 versions of the ASHRAE standard replace the lighting controls credits provided in the 1989 version with mandatory control requirements. These new requirements are intended to reduce energy usage by requiring automatic controls that switch off lighting loads in unoccupied spaces.

Both the 1999 and 2001 versions require that spaces over 5,000 square feet (with certain exclusions, such as emergency lighting) must be controlled by an automatic shut-off device (i.e., either a scheduling system, occupancy sensors, or a control signal from another control or alarm system). Further, each space enclosed by ceiling-high partitions must be controlled by an independent control (typically an occupancy sensor) that controls the primary lighting. Both versions also require that spaces up to 10,000 square feet must have at least one control per 2,500 square feet and that larger spaces must have one control per 10,000 square feet. Exterior luminaires must also be controlled by either a photocell or scheduling system which accounts for seasonal changes in available natural light.

Separate control devices are also mandated for the following applications:

• Display/accent lighting
• Case lighting
• Hotel/motel guest rooms (must have a master control device placed at the room entry)
• Task lighting
• Nonvisual lighting (e.g., lighting used for plant growth and food warming)
• Demonstration lighting (for sale or for lighting demonstration).

Although the 1999 and 2001 versions of the ASHRAE standard do not explicitly address dimming, the additional energy savings produced by dimming systems may be considered when calculating overall building energy.

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