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LD+A The Magazine of the Illuminating Engineering Society of North America

LED Testing & Application  

Advanced Control Options for LEED v4

A recent article in LD+A by Gary Meshberg, chair of the Lighting Controls Association and sales director for Encelium Technologies, took a look at how the bar will be raised for earning LEED points in the new LEED v4 to be released soon. One change appears almost certain: updating the prerequisite for the Energy + Atmosphere section from compliance with ASHRAE/IESNA 90.1-2007 to compliance with ASHRAE/IESNA 90.1-2010, since the latter is the new national energy reference standard. By mid-October 2013, all states must have in place a commercial building energy code in place at least as stringent as the 2010 version of 90.1 or justify why they cannot comply. This means it will be much tougher to beat the baseline prerequisite to achieve a meaningful lighting energy reduction and resulting contribution to LEED Energy + Atmosphere points. The designer will be encouraged to emphasize LED sources and advanced lighting control solutions and/or utilize design strategies such as task/ambient lighting.

The challenge, then, is figuring out what these advanced lighting control options might be. ASHRAE/IESNA 90.1-2010 now includes far greater restrictions in terms of lighting controls, requiring automatic shutoff, bilevel lighting and daylight harvesting in a broad range of applications. Because these strategies are mandated by the standard, compliance is only good enough to satisfy the LEED prerequisite. This means that if the design does not meet ASHRAE/IES Standard 90.1-2010, the project does not qualify for LEED certification.

Are there any other options? An answer may be found in the standard itself: 90.1-2010 lists a series of advanced lighting control options in Table 9.6.2, including:
  • manual or programmable dimming control (must be combined with occupancy sensing in meeting and training spaces)
  • multilevel occupancy sensors controlling the downlight component of workstation-specific luminaires with continuous dimming to OFF, which may be combined with occupant dimming of this downlight component
  • automatic bilevel or multilevel switching or continuous dimming daylight harvesting control in primary daylight zones under restrictive conditions related to effective aperture and size of zone
  • automatic continuous dimming daylight harvesting control in secondary sidelighted daylight zones with a daylight aperture considered large enough.
The standard identifies these strategies as design options that can be enacted to earn an interior lighting power adjustment credit if the interior lighting is designed using the Space-by-Space Method of compliance. They may be applied as long as all mandatory controls are also provided for the given space.

Here is how it works: Each strategy is assigned a Control Factor by space type—open office, private office, meeting space (including classrooms) and various public spaces. The Control Factor may be as low as 0.05 (e.g., manual dimming in a private office) and as high as 0.30 (occupancy sensing controlling the downlight component of workstation-specific luminaires with continuous dimming to OFF combined with personal continuous dimming). The following formula is used:

Additional Interior Lighting Power Allowance = Lighting Power Under Control (watts) x Control Factor (specific to the given control strategy by space type, from Table 9.6.2).

For example, if manual continuous dimming is employed in a retail sales area, the control factor is 0.10, meaning if 1,000 watts of lighting is controlled by manual dimmers, 100 watts of additional lighting power is gained for use in the design anywhere in the building.

This is a welcome addition to the standard, as it encourages more aggressive control options in exchange for greater design flexibility. Is there a potential for LEED? The question is whether the additional lighting power could be claimed as savings instead of used as additional power.

If this were the case, Table 9.6.2 would provide a handy guide to control options that can be deployed to go beyond 90.1 and contribute to LEED Energy + Atmosphere points. The standard even provides a way to calculate projected savings that would be acceptable to USGBC.

The Lighting Controls Association, administered by the National Electrical Manufacturers Association, contacted the USGBC about this issue and received this reply:

"If a project is pursuing LEED certification using the building energy simulation option (modeling per ASHRAE 90.1-2010), and the optional lighting controls are installed, the additional lighting power allowance would be added to the baseline building lighting power allowance for that space. Any reduction from that value in the proposed building could be claimed as savings."

This means Table 9.6.2 identifies a significant number of control options that can be used, among others, to reduce energy consumption and thereby contribute to LEED Energy + Atmosphere points, if energy modeling will be used to demonstrate compliance.

This may be beneficial for designers of lighting systems in LEED projects, as it opens a range of lighting control strategies that can be enacted to exceed the minimum standard criteria and earn LEED Energy + Atmosphere points, with the suggested savings built into the standard.

New LED luminaires are being offered standard with 0-10VDC dimming and in some cases without a premium for the dimming. Utilizing efficient fluorescent dimming solutions has also become more cost effective in recent years. Controllable, highly efficient lighting, coupled with advanced lighting controls, present opportunities to exceed the 2010 version of the 90.1 standard and earn LEED v4 points while providing greater lighting value.



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