Let’s start an AV presentation in your conference room. Why does the lighting ramp up to max as you pull the shades against the daylight?
In a dark parking garage, only the light directly overhead responds to your presence. Oh, you wanted an occupancy sensor that illuminates banks of lights in a wide area around you?
You’ve set up five different scenes for your expensive hotel lobby. Did they really need to crossfade?
A demand response signal cues an automatic 15% reduction in the building’s lighting power. It was way cheaper to just control a third of the building and dim the lighting there 45%.
During a project’s schematic design phase, designers and engineers create a master preliminary document: the Basis of Design. This narrative translates the Owner’s Project Requirements into building systems and includes general design requirements, sustainability measures, space design qualities and assumptions (indoor and outdoor), loads and systems descriptions, etc.
While the Basis of Design is not part of the contract documents, and is therefore not enforceable, it forms a basic understanding of the project concept. It is subject to change, but essentially guides the subsequent process. “Honestly, the Basis of Design forces design engineers think about what they’re doing before they put it in the plans and specs,” described Lyn Gomes, commissioning project manager at kW Engineering.
A number of lighting-specific design parameters are commonly included in the Basis of Design: e.g., targeted light levels, light qualities and lighting power densities; possible LEED credits; reflectances; descriptions of luminaire systems; and – crucially – Lighting Control Intent. The Lighting Controls Narrative (a.k.a. Control Intent Narrative) included in the Basis of Design is a plain-language version of the desired level of lighting controls complexity and a description of how lighting controls are intended to work; area-by-area, over time.
What are the triggers? What happens in response? Which cue overrides which cue in which spaces? What level of automation is required? “A good, thorough Control Intent Narrative will break it down not just by the individual space-level control descriptions, but you also have building-level controls. Those would be things like demand response, timeclocks, emergency lighting; maybe at the building level there is integration with other control systems like HVAC,” explained Gomes. “It’s important to cover it from both a very granular level, but also a very big, overall level in terms of different spaces in the building. Then you also look at it by different scenarios.” Space use, tasks and operations over time are all considered. “You can put it in very general language, so you can reuse it on other projects. Of course, that doesn’t get you out of modifying it so it’s project-specific,” she added.
If the system design is described in the spec and construction documents, why put the time and effort into explaining all the functionalities up front in the Control Intent Narrative? “If you don’t define it, then who knows what’s going to be the final result? It’s an unexpected burden to expect a contractor, a vendor, a lighting controls manufacturer to read the minds of the design team and the owner,” said Rick Miller, principal of RNM Engineering, Inc. This has advantages all around:
- The owner approves it, and knows what they’re going to get.
- The designer is far more likely to get what they expect and is protected (somewhat) if the system as delivered falls short or if the owner changes requirements or makes inconsistent “suggestions.”
- The bidder has a bigger picture of what’s entailed.
- The contractor is more likely to get the installation right, the first time.
- The vendor is more likely to provide what’s wanted, without making assumptions.
“It helps a whole list of everybody along the chain,” said Miller. “But it is important to acknowledge that to give the level of thoroughness that you need to do it right, you need to put a significant amount of effort into the Basis of Design.”
Jeremy Windle, director – lighting studio at StudioK1, emphasized the importance of listening to the owner and using functional parameters in the Control Intent Narrative. “If I can accurately explain how the lighting controls all work together, that puts the onus on the manufacturer to make sure that their system does what I expect it to do.”
“If you just install the equipment, it doesn’t necessarily mean that you’re going to realize all of the potential energy savings,” said Angela McDonald, supervisor at PG&E’s Pacific Energy Center. “Even if you initially realize your intended energy savings, but the end-user isn’t happy with the way that you’ve set the system up, they’ll find ways to work around the system. They’ll undo or defeat the effort that you have made to save energy.” It is not uncommon to see snapback – or “user revolt” – where occupants substitute, disable or partially reprogram a lighting controls system that doesn’t meet their needs. If an owner gets burned on an advanced lighting controls project, they’re also less likely to include that technology in the future (a broader snapback). McDonald sees the Control Intent Narrative as the opportunity to partner with owners and occupants to achieve persistent energy savings.
“IoT and connected lighting are forcing even more of a need to define things. What does a connected lighting system mean?” asked Miller. “What are the benefits that somebody wants to get out of that system?” A Control Intent Narrative would define how the lighting controls system interacts with non-lighting data streams.
The Sequence of Operations (sometimes seen as Sequence of Operation) narratives and spreadsheets take lighting controls to a whole ‘nother level of specificity. Both Gomes and Miller recommend including a lighting controls schematic drawing. It describes a hierarchy of controls and acts to limit misinterpretations and avoid substitution to lighting controls systems that are not truly equal in capabilities. With a schematic drawing, it’s less likely that a wired scheme would be substituted for wireless or that integrated controls would be substituted for a slaved network. Even with a sole-source specification – according to Gomes, there’s nothing wrong with a sole-source spec – a schematic might alert an integrator or manufacturer to needed parts and pieces. Also, a schematic would show building-wide dimming in response to a demand response signal. Gomes emphasizes that the network diagram be specific for the project and detail every space in the building. “I have personally witnessed that 90% of projects with incomplete or generic network diagrams had an incomplete or non-existent network installed.”
In construction documentation, a complete Sequence of Operations must contain a high level of detail and specific programmable features. Often articulated in a Controls Matrix, these might include footcandle-level setpoints, timeouts, timed sweeps, high-end trims, transition times, and percent dimming levels. Zones and scenes are described along with precisely how they respond to actuators and tie-in with other systems, such as HVAC or security.
“Yes, this takes a lot of time,” said Windle. “But what this means is that I don’t have to be on the job site for the first 2 days. This explains to the technician what happens on time of day, what the button presses should do, and then what all the levels should be.” By giving the technician all the information up front, they’re not guessing or just doing what they did last time. Windle said he is then set up to come through a week into startup and just review all the scenes make any needed adjustments. If the project requires a commissioning provider, the Controls Matrix creates a rubric to evaluate and adjust the system. Otherwise, they’re relying on the contractor’s preferences and the code.
“We will specify a job 2 years before it’s built. When I go back 2 years later, I may not remember what I wanted it to do,” Windle added. Is the contractor likely to send an RFI, or just leave it at the factory default?
Gomes and Miller are leading up a task force for the Illuminating Engineering Society to develop a Recommended Practice for using a Control Intent Narrative in the Basis of Design, and then creating a more specific Sequence of Operations. They also conduct classes on this topic at the PG&E Energy Centers, online and elsewhere.
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