How the energy code changed lighting design
Newer energy codes put an emphasis on understanding lighting control requirements before determining the lighting design requirements
- Learn how documenting lighting control requirements is a critical step in lighting design.
- Understand how starting with a lighting control strategy before a lighting design strategy can help reduce complications in lighting controls and design.
- Document lighting control spaces and subspaces based on the energy code to help guide the lighting design.
In the past, automatic lighting control was primarily focused on energy cost savings. Before widespread availability of highly efficient LED lighting technology, it was almost a “no brainer” to install some kind of lighting control to turn off lights when they were not in use.
Therefore, occupancy sensors and on/off switches were widely used as the control strategy for many space types. The cost of implementing a stand-alone occupancy sensor or a simple zoned relay system with timeclock control offered a very quick payback to the owner.
When the 2007 edition of ASHRAE Standard 90.1: Energy Standard for Buildings Except Low-Rise Residential Buildings was put into effect, it was not a big stretch for building owners to accept these requirements for this basic level of automatic control. Users could still enter a space and turn lights on and off with the traditional toggle switches and the occupancy sensors or timers generally did not impact the user experience as they were intended to operate in unoccupied spaces. Most owners generally accepted that the lighting didn’t need to be on when a space wasn’t in use. Saving the energy and the cost of the energy made sense.
In 2017, Michigan adopted the 2015 Michigan Energy Code that adopted, by reference, ASHRAE 90.1 — 2013. Before this update, the 2007 version of ASHRAE 90.1 was the referenced standard per the 2009 Michigan Energy Code.
Although not seemingly significant, the jump from the 2007 version to the 2013 version of ASHRAE (two code cycles) resulted in significant changes, particularly as it relates to lighting controls. Other states across the country (California, for instance) have been much more progressive with respect to energy code adoption.
However, the architectural, engineering and construction communities in Michigan and many other Midwestern states have not had to contend with the design, specification and construction challenges associated with these requirements. In addition, the end user community had not experienced the user interface with more sophisticated lighting control systems.
Adopting new lighting codes
The adoption of a more robust and restrictive energy code caught many in the Michigan AEC industry by surprise and did not make for a smooth transition between codes. Not only did specifiers have to quickly educate themselves on these new requirements, but they also had to scramble to learn how to design and document lighting control systems that would comply with these new requirements.
Contractors and suppliers were faced with new challenges of pricing, procuring, installing and commissioning complex lighting control systems that many had never experienced before. To complicate matters further, architects and owners were surprised by the need to provide a more sophisticated lighting control system to meet the new requirements and there were often (and still are) conflicts between the intended function and operation of spaces and the requirements of the new energy code.
Lighting designers and electrical engineers found themselves having to defend their designs with questions and comments such as:
- “Why do I have to do this? I never had to do that before.”
- “I didn’t have that in my budget.”
- “I don’t want to do that — do I have to?”
- “The code officials aren’t enforcing it, so why do I need to do it?”
- “Why can’t I just have a switch on a wall?”
With the introduction of ASHRAE 90.1-2013, there were significant changes that impacted the user experience such as requirements for bi-level lighting control, daylight responsive control and manual ON. With bi-level lighting control or manual ON control, the user must decide what light level to select.
This isn’t a difficult choice for a private office, but it becomes challenging in an open office where occupants are likely to disagree on the desired light level. Daylight responsive controls are programmed to maintain a certain illuminance level based on the amount of daylight, leaving the user with no control. It is not uncommon for occupants in an open office with newly installed daylight responsive controls to call the facility manager to report “problems” with the lighting.
With the newer code, reaching for the traditional standard toggle switch to turn the lights on no longer satisfies the requirements. Users must now reach for a local control device and decide what light level they want and allow automatic features of the system to work, regardless of their desire to intervene.
Not only did the changes of the new energy code disrupt owners and users, it also created challenges in the design workflow. In the past, it was common for an architect to make a first pass at a reflected ceiling layout and select a type or style of lighting for the space. The electrical engineer would then run lighting calculations to confirm or adjust the spacing and/or the number and output of the lamps and select a specific type of product to achieve the proper lighting levels. Decorative lighting or sometimes lighting for effect, was often layered onto a general lighting strategy.
Once all that was worked out, the engineer would then circuit the lighting and apply the basic controls to the layout (see Figure 2). ASHRAE 90.1-2007 had requirements only for automatic lighting shut-off including some specific spaces requiring occupancy sensors, therefore they were not difficult to overlay onto the lighting design for compliance.
When the more complex and restrictive requirements of the 2013 version were adopted, it became much more difficult to follow this same workflow and overlaying the lighting control strategies often did not mesh with the desired product selection and layouts. It became apparent that the flow of design relating to lighting and lighting controls needed to shift.
Many spaces now require bi-level lighting control, which was usually accomplished by adding dimming controls regardless of the owner needing or wanting them. Adding dimming controls for the lighting in a space added complexity to the controls, especially if there were multiple light fixture types with different dimming types such as 0 to 10 volts and electronic low voltage.
Furthermore, there is often a desire to control lighting in a way that supports the intended use of the space — conference rooms, ballrooms, multipurpose rooms all have unique programmatic needs for lighting control that are in addition to the energy code drive control requirements. These two need to work together to allow for a simple and positive user experience.
Meeting lighting design challenges
A common challenge faced with implementing the code required primary and secondary daylighting for the area adjacent to a window is when light fixtures cross over both daylight zones. A common example of this is where a 16-foot linear light fixture is positioned perpendicular to the windows crossing over both daylight zones (see Figure 3).
ASHRAE 90.1-2013 requires general lighting in the secondary daylight area to be controlled independently of the general lighting in the primary daylight area. With a 16-foot light fixture spanning two daylight zones, the fixture must now be designed to allow for each half of the light fixture to be on a separate relay controlled by an independent daylight sensor.
This could be an acceptable solution to the owner and design team, but in many cases it is not. If the primary daylight zone is dimmed to a different level than the secondary zone, then each half of the 16-foot fixture will appear different. To someone unaware of these code requirements, they may assume the light fixture is broken because it is typical to see the entire length of a linear light fixture appear the same. In addition, this condition requires a fixture that is intended to be a single, continuous element with a single power feed to now be broken into two elements with two power feeds.
To alleviate this potential issue, daylighting zones should be documented first. Then the lighting can be layered into the plan keeping in mind the constraints of the daylight zone. This will simplify the lighting controls and the light fixture specification. In this example, a 6-foot linear fixture was used in each daylight zone to allow the light fixtures located within those zones to easily be controlled separately (see Figure 4).
Daylighting from skylights and roof monitors can also present a similar problem as windows, where lighting crosses over multiple daylight zones. In many cases, this scenario can create even more complex issues as this typically affects interior areas where control zones and functions can be even more blended.
Another common challenge faced when implementing code requirements is how to deal with different space types that are open to one another. In an open office environment, spaces like corridors, print rooms, office workstations and informal meeting areas blend with no real separation between them.
When applying ASHRAE 90.1-2007 to an open office, the code allowed for the entire space to be designated as one space type that most closely represented the proposed use of the space. ASHRAE 90.1-2013 revised this section and requires a space with multiple functions to be broken up into smaller subspaces and then choosing a space type for each subspace.
When lighting is designed for open office areas, there is often one light fixture type used throughout the space to provide uniform lighting regardless of the specific use of space below the light (see Figure 5). This lighting strategy makes it very difficult to apply the subspace control requirements.
For example, a corridor has slightly different control requirements than an open office. So, when a continuous linear light fixture extends from the open office over the corridor to the adjacent open office, it adds lots of complexity. Controlling just the section of a continuous linear light over the corridor results in an additional driver and power feed for that section. This creates the same problem described above with the daylighting zones, a continuous fixture will have sections that appear different and may be perceived as broken.
To alleviate this potential issue, the subspaces should be documented before the lighting has been laid out (see Figure 6). Now the subspaces can help inform where lighting can be placed so it can be controlled appropriately and efficiently. One lighting layout can be used in the open office area and another can be used in the corridor, allowing for two different control strategies to easily take place (see Figure 7). This also will provide visual reinforcement to the occupants of the intended use of the spaces open to one another. When lighting is used to differentiate the open office area from the corridor or an informal meeting space from the open office, it can help with wayfinding for the users of the space.
Electrical engineers, designers and architects can benefit from modifying the workflow we have been accustomed to for years by first documenting the control requirements. This includes the control requirements dictated by the energy code and the owner’s programmatic requirements. Once these are defined and accepted, then the overlay of architectural ceiling systems, coves and details can support the different control needs.
Next, light fixtures can be selected and located to support the control zones and the architectural ceiling elements. Then lighting calculations can be performed and finally, the lighting can be circuited. (see Figure 8).
This relatively minor change in workflow should result in a much more streamlined approach. It will inform the architectural ceiling design in a way that supports the control strategies, then narrow down the range of lighting product that will support the architectural ceiling design. Ultimately, the entire space will become more cohesive and the user interface will seem more intuitive and natural. Groups of lights dimming in response to daylight availability will not seem odd or disconcerting and ideally not even noticed. Costly modifications to standard products to achieve the energy code requirements, can therefore be avoided.
Looking forward, LED technology has opened up a wide range of form factors for lighting fixtures and architecturally integrated lighting. The ability to layer lighting products presents a new level of creative opportunity for architects and lighting designers, but at the same time, the choices can seem overwhelming. By defining the control requirements, goal posts can be set for the designers that will not limit creativity but guide it.
Peter Basso Associates is a CFE Media content partner.