ASHRAE Journal - June 2012 - 96

emerging technologies

control systems & leeD
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By Alissa cooperman; John Dieckmann, Member ASHRAE; and James Brodrick, Ph.D., Member ASHRAE

ypically, the largest energy consumers in commercial buildings are lighting and HVAC systems. Under the latest revision of LEED, 2009

v3, many of the points needed to obtain LEED certification can be acquired through LEED credits that require or suggest the implementation of control systems for lighting, HVAC, and/or the entire building.
The point thresholds for the different levels of LEED certification, based on LEED-NC 2009, are outlined in Table 1.3 The most recent revision of LEED-NC emphasizes energy efficiency and indoor environment quality. This is reflected in the significant increase in potential points in the Energy & Atmosphere credit category from 17 in v. 2.2 to 35 in v. 3.2,4 Other LEED systems have similarly high point allotments in the energy and atmosphere section. This column outlines where and how the use of control systems has been integrated into qualifying for LEED points for certification. LEED-NC (New Construction and Major Renovations) is used as the reference rating system. The need for using control systems is evident by their being mentioned specifically throughout the Energy and Atmosphere, Indoor Environment, and even Site Sustainability credit categories. Points can be attained by reducing light pollution, optimizing and monitoring the building’s energy performance, controlling lighting, and providing a comfortable and safe indoor environment. Table 2 summarizes some of the credits that can be gained with the help of control systems.3 Table 2 totals a possible 29 points obtainable through strategies in which controls play an integral part. For example, the LEED-NC 2009 guidance suggests input power reductions for interior lighting after hours with limited override determined by occupancy sensors, and suggests CO2 and airflow sensors to trigger the HVAC system directly or to trigger the building automation system to alter the ventilation/outdoor air delivery as needed by the interior. To accomplish the Measurement & Verification credit, energy consumption trend monitoring systems and control system diagnostic alerts are suggested. For the Lighting Controllability of Systems credits, occupant based control and task based controls are suggested.3 One company claims that the use of their lighting energy management system with occupancy and photo sensors and a variety of control strategies (time scheduling, occupancy control, task tuning, etc) can help to gain any of the 29 points listed.5 Overall, LEED 2009 encourages automated and manual controls as a means to reduce building energy consumption and to improve the building’s indoor environment and outdoor environmental impact.3 It takes 40 points for a building to become LEED certified. Thus, it is feasible to obtain a large fraction of the points needed for LEED certification by choosing to meet credits that suggest or require an energy control system. With current technologies and software, lighting and HVAC systems can be automatically controlled, scheduled, and monitored based on occupancy, space use, and time of day. This leads to energy savings and can be applied for LEED credits.
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One company’s building automation system monitored the HVAC system using CO2, outdoor airflow, temperature, and relative humidity sensors. This system ensured 30% more outdoor air than required by ASHRAE Standard 62.1; this garnered 1 LEED-NC point. It also provided a 6% reduction in natural gas and 1% reduction in electricity consumption, again contributing to acquiring LEED points. The building’s use of daylight set the baseline lighting energy consumption 15% below ASHRAE-compliant buildings and another 6% savings were gained with the controls used. In all, the building reduced its energy use by 25% compared to precommissioning levels.6 CBECS (Commercial Building Energy Consumption Survey) 2003* data shows that daylight sensors are used in only roughly 2% of lit commercial space, and lighting energy management and control systems are used in only a little more than 1% of lit commercial space.7 Energy management and control systems for HVAC are used in about 5.5% of surveyed commercial buildings.7 A great potential for energy savings exists in the 95% to 99% of buildings that have yet to adopt energysaving control systems. Commercial building lighting consumed 3.69 quads of energy in 2010, 20.2% of the total primary energy consumed by commercial buildings that year.8 In addition to fixtures that consume less energy, control strategies to reduce lighting use and energy consumption could save significant amounts of energy if widely implemented. One company offers addressable dimming controls. This allows for control
* CBECS 2003 is the latest dataset as the CBECS

2007 dataset was deemed invalid for lack of statistical significance and other reasons. CBECS 2012 is currently in progress to be released in 2014.

ASHRAE Journal

June 2012

ASHRAE Journal - June 2012

Table of Contents for the Digital Edition of ASHRAE Journal - June 2012