Decoding the Energy Codes

Energy storage.

Late last year, ASHRAE, the American Society of Heating, Refrigerating and Air-Conditioning Engineers, published the 2019 version of ASHRAE/ANSI/IES 90.1, “Energy Standard for Buildings Except Low-Rise Residential Buildings,” the model commercial building energy code. For lighting, the new version most notably modifies interior power allowances, updates some control requirements and provides contractors a new simplified compliance method for office, school and retail buildings.

Commercial building energy codes regulate the designed energy efficiency of nonresidential buildings. Therefore, they remain a major driver in demand for energy-efficient products, such as LED lighting and advanced controls. While a majority of states use the International Energy Conservation Code (IECC) as a model, 90.1 is significant because it is recognized by the U.S. Department of Energy as the national reference code and by initiatives such as the LEED green building rating system. The IECC also recognizes 90.1 as an alternative compliance standard.

What’s new in the 2019 version

Lighting power: The standard imposes maximum interior lighting power allowances for the whole building (building-area method) and by space (space by space method). The 2019 version adjusted these allowances based on modeling that, in turn, is based on real-world conditions and updated Illuminating Engineering Society light-level recommendations.

While interior lighting power allowances were raised for several building types—automotive, exercise center, gymnasium, library, parking garage and workshop—those for all other building types were reduced. The level of reduction varies by application, with some, such as warehouses, seeing a modest reduction, 0.48 to 0.45 watts per square feet (W/sq.ft.), or 6%—and others seeing a major reduction—such as museums, 1.06 to 0.55W/sq.ft., nearly 50%.

Among the most prevalent building markets, the office building maximum interior lighting-power allowance reduced from 0.79 to 0.64 W/sq.ft., a nearly 20% drop. The allowance also reduced from 1.06 to 0.84W/sq.ft. for retail, similarly a roughly 20% drop; 0.81 to 0.72W/sq.ft. for schools/universities, a roughly 10% drop; 1.05 to 0.96W/sq.ft. for hospitals, a nearly 10% drop; and from 0.90 to 0.82W/sq.ft. for manufacturing facilities, also a nearly 10% drop.

For exterior applications, with a few exceptions, the maximum lighting power allowances were unchanged, while the standard added a provision for calculating the power allowance for applications not listed or not comparable with any listed on the table.

New compliance path: For buildings in which at least 80% of the floorspace is used as an office, retail or school building, the 2019 version of 90.1 offers a new, simplified building-area method. This compliance path can be used for interior and exterior lighting, though calculated and complied with separately, for new buildings and tenant improvements under 25,000 square feet.

A series of tables identifies lighting applications in office, retail and school buildings, along with maximum lighting power allowances and associated control requirements. Another table lists exempted lighting applications for all three building types.

A notable exception is luminaire and lamp/ballast replacements, in which the owner may comply by ensuring a minimum reduction of at least 35% for existing fluorescent T12 systems, 20% for T8 or T5, 45% for high-intensity discharge (HID), and 75% for incandescent. Controls are not mentioned as part of this exception clause, though note that earlier in the standard’s lighting section, either compliant occupancy, or time-based automatic shutoff controls, are required as part of the install if more than 20% of the connected lighting load is being replaced.

Controls: The standard imposes a broad range of automatic lighting controls to reduce energy consumption. The 2019 version updated the lighting control requirements for parking garages to account for the use of LED technology, updated daylight-responsive control requirements, and added a definition of “continuous dimming” based on NEMA LSD-64-2014.

Parking garage lighting has its own particular control requirements recognized in the standard. The 2019 version requires lighting power for each luminaire to be reduced by at least 50% when no activity is detected for 10 minutes. Parking garage transition lighting is also addressed.

For daylight areas, the photocontrol must reduce lighting power by continuous dimming and in response to daylight by at least 80%, including off. If another partial-off control reduces lighting power, the daylight-responsive control can adjust in response to daylight but may not increase power above the partial-off control level. Similar to requirements already in effect for sidelighted spaces, calibration control for toplighted spaces must be located 11 feet or lower above the finished floor and must not require the physical presence of a person at the sensor while the processing takes place.

Overall, the most notable change in ASHRAE/IES 90.1-2019 is an attempt at simplifying compliance. Also, it is more stringent in terms of interior lighting power allowances in recognition of the growing maturity of LED lighting. For more information, consult the authority having jurisdiction and the energy code applicable to your jurisdiction.

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