Best practices for HVAC and lighting controls integration

Follow these best practices to successfully integrate lighting and HVAC systems while also ensuring code compliance.

03/15/2018


This article has been peer-reviewed.

Learning objectives:

  • Understand how lighting systems can be integrated with HVAC systems.

  • Learn about the codes and standards, such as ASHRAE 90.1, that help define energy efficiency standards.

  • Know how to integrate controls to ensure all systems integrate effectively.


For decades, the design industry has looked at lighting as the “low-hanging fruit” of improving a building’s energy usage. In 2005, the U.S. Department of Energy reported that lighting energy accounted for more than 25% of all commercial-building energy consumption. Since then, there’s been an evolution in lighting technologies, from compact fluorescent lamps (CFL) and high-performance T8 technology to LEDs coupled with advances in optics, materials, and fixture design. These advances have allowed simple and cost-effective lighting fixture changes that result in lower energy expenditures and large incentives from utility rebate programs. These vast improvements have lowered the energy usage of lighting by more than 25% in 2005 to 11%, as reported by the U.S. Energy Information Administration in 2016. Now that LED technology and advanced lighting controls are more prevalent, it is likely that there will be even more reductions.

Figure 1: Controls integration can save energy by reducing airflow rates and lighting levels in operating rooms when not in use. Courtesy: Laura Peters, CannonDesignAs lighting technologies have changed, HVAC systems and their controls have also continued to advance. Electronically commutated motors (ECMs), variable-speed compressors, and more widespread use of advanced control technologies continue to reduce energy usage. While lighting and HVAC technologies have individually progressed, integrating their controls has not been widely accepted and implemented for construction projects. HVAC and lighting control manufacturers have each developed their own solutions to solve their clients’ problems, while building owners are reluctant to have a single source of responsibility for these functions. This article shares best practices, future possibilities, and a case study that demonstrates success and lessons learned when integrating lighting and HVAC controls.

ASHRAE 90.1 and system integration

One of the more common energy standards adopted as code in the United States is the 2013 version of ASHRAE Standard 90.1: Energy Standard for Buildings Except Low-Rise Residential Buildings. This standard outlines several prescriptive strategies for lighting control that must be implemented based on space type. For a majority of commercial building installations, in addition to manual control for lighting, several other automated measures must be implemented. Depending on the space type, these measures may include occupancy/vacancy, daylighting, and auto-off or scheduled lighting control strategies. These “mandatory provisions” are spelled out in Section 9.4.4.1 of ASHRAE 90.1. To accomplish these prescriptive requirements, there are usually several devices required to enable these control functions to be carried out.

Figure 2: Controls integration can save energy by reducing airflow rates and lighting levels in operating rooms when not in use. Courtesy: Laura Peters, CannonDesignASHRAE 90.1 similarly lays out recommendations that can automatically shut down HVAC systems in an effort to conserve energy. Section 6.4.3.3.1 calls out several strategies to accomplish this, which include scheduling, occupancy sensors, manually operated timers, or an interlock to the security system that shuts down the HVAC system when the security system is activated. These strategies have their place and do not apply to every space type, especially those where shutting down the HVAC system could potentially cause harm to building occupants (e.g., in a laboratory or hospital isolation room).

Even before codes required lighting and HVAC controls, savvy engineers recognized the opportunity for owners to save energy and material costs by using shared sensors to perform multiple building system functions. The most common form of lighting and HVAC controls integration is to select a room-occupancy sensor for the lighting controls that has an auxiliary low-voltage contact. The contact is wired to the HVAC control system and may turn a fan coil or heat pump on/off, turn down a variable air volume box, or be used to reset room-temperature or airflow-control setpoints. ASHRAE Standard 62.1-2016: Ventilation for Acceptable Indoor Air Quality will allow for certain space types to reduce ventilation airflow to zero when the space is unoccupied, according to Table 6.2.2.1, Minimum Ventilation Rates in Breathing Zone, in ASHRAE 62.1. As this new version of the standard becomes more widely adopted, further energy savings can be realized. Combining lighting and HVAC controls in this manner is relatively easy to implement in most commercial buildings, especially where populations tend to be transient. For example, occupied conference rooms cause lower office occupancy rates. Empty spaces, like the offices, do not need lights on and HVAC systems maintaining peak occupancy conditions. Some versions of the code take this optimization to very granular levels—requiring that systems also be wired to control switched receptacles in the rooms to make sure other powered devices aren’t using energy when the room is unoccupied. (See case study for more strategies).

Taking this basic level of integration a step further, these strategies can also be applied in settings with a different intent: enhancing safety. For instance, in operating rooms, ASHRAE Standard 170-2013: Ventilation of Health Care Facilities, paragraph 7.1.a.3, allows the following:

“For spaces that require a positive or negative pressure relationship, the number of air changes can be reduced when the space is unoccupied, provided that the required pressure relationship to adjoining spaces is maintained while the space is unoccupied and that the minimum number of air changes indicated is re-established anytime the space becomes occupied.”

Figure 3: Occupancy control can be used to save significant amounts of energy and as a backup safety mechanism to manual or scheduled controls. Courtesy: Laura Peters, CannonDesign In the case of operating rooms (ORs), air-change rates can typically be reduced from 20 ACH (or more) down to 6 ACH (or less) when the room is not in use, saving a tremendous amount of energy. Historically, the airflow change has been initiated by using time schedules. The same time schedule may also reduce lighting levels within the space. In a typical operating suite, a set number of operating ORs may not be allowed to setback to lower air-change rates or lighting levels so that they are always “ready” for emergency surgical procedures. Alternatively, a nurse manager may need to manually initiate occupied modes for operating rooms during off-hours surgical procedures. Occupancy sensors can simplify this, reinstating the proper minimum air changes and adjusting lighting levels within the space when the space is occupied during the timed unoccupied schedule. Using multiple redundant sensors with proper programming can ensure that occupancy is sensed and avoid any pitfalls of not returning the room to normal duty from unoccupied modes.

Instituting similar strategies in other occupancies, such as laboratories, where high air-change rates are needed for the health and safety of the occupants, but it’s not critical when the spaces are unoccupied. The 2013 version of ASHRAE 90.1, Section 6.7.7.2, indicates that laboratories must follow one of three set criteria, two of which involve reducing air-change rates within spaces. Just like operating rooms, occupancy/vacancy sensors reduce lighting levels and adjust HVAC air-change rates to conserve energy. Designers must proceed with extreme caution when applying these solutions, as the occupants’ environmental health and safety must take precedence over any energy-savings strategies.

While the aforementioned solutions all involve hardwiring an occupancy sensor to the HVAC controls system, more recent projects now take the additional contacts (and additional wiring associated with them) out of the equation. Instead, BACNet or LonWorks open protocols are used over a common communication network to process the occupancy signals. The hard-wired control points that were once directly wired to HVAC equipment controllers now become virtual. As programming, hardware, and protocols continue to mature and become more reliable, this type of approach will become easier and lead to greater benefits from a networked solution.


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