Intended Goal/Desired Outcome: Reduce the energy consumed by the lighting system and increase lamp life in a renovated elementary school through installing occupancy sensors to automatically turn on and shut off lights as part of the lighting control system.
Less than Ideal Actual Outcome: In some of the classrooms and restrooms, there is an occupancy sensor delay in turning the lights on after you enter the space. This confuses the younger students and is annoying to the adults who end up having to walk almost to the center of their classroom for the lights to turn on (if coming in through the door without the control station).
The younger students (particularly K-1) are “confused” by the restroom occupancy sensor control because of the delay in the auto-on when entering; sometimes they have to waive their hands in big motions for sensors to “see” them. The older students tease the younger students by telling them the restrooms are haunted, scaring some of the younger students. Some of these younger students end up avoiding using the restroom or rushing through the process, resulting in:
- concentration/performance issues in the classroom (from holding longer than they should as well as the dread of going to the restroom),
- hygiene issues in the restrooms (from rushing through the process and getting urine and water everywhere) and
- potential health problems (from consistently holding longer than they should).
Low SES (socioeconomic status) students are disproportionately impacted by facility problems impacting comfort and health, such as these, for a variety of reasons, in part related to having on average less support outside of the school. And this rural elementary school has a large percentage of low SES students, making it doubly important to rectify these issues and in general avoid them to begin with.
While it hadn’t happened at this school yet (by the second year of occupancy), we often see the occupancy sensors disabled when such problems aren’t rectified because of the consistent complaints of the occupants. This reduces energy savings, and in the case where manual control isn’t available (i.e., the restrooms in this school), this results in more energy usage than if manual only control had been used, because the lights end up being on all of the time.
What went wrong or appears to have gone wrong? Two things primarily:
- The lighting control system was not included in the commissioning of the building’s systems, something that should have been considered more during planning/design and worked into the overall budget if possible. This likely would have uncovered at least most of the issues mentioned below prior to occupancy. And enhanced commissioning may have avoided most of these problems entirely.
- Potentially occupancy sensor adjustments may be needed to sensitivity, aiming and/or time delay, and in some instances sensors may need to be relocated and/or additional occupancy sensors added. None of these issues had been effectively examined at the time of the evaluation.
- In the restrooms, the ballasts may need to be changed from rapid start to instant start. Instant start ballasts will result in gained energy savings, but frequent on/off operation may shorten the lamp life by approximately 50%. However, changing out to LED downlights would circumvent the rapid start vs. instant start pros/cons.
- In most cases, manual-on/auto-off control is recommended over auto-on/auto-off control (use “vacancy” sensors instead of “occupancy” sensors). This will avoid delayed-on and false-on occurrences, reducing energy consumption, potentially extending lamp life and give some of that control back to the occupant.
- The maintenance of the lighting control system fell through the cracks primarily because it ended up being too complicated for the district to work with, and this was not adequately accounted for during planning/design. The integration of the manual wall controls, photocells, occupancy sensors and solar tube controllers is complex and the local electricians have trouble working on the whole system. The school custodian and district O&M personnel didn’t really understand the system that well (including making occupancy sensor adjustments) and neither did the teachers.
- As a result of the perceived lack of personal environmental control created among the teachers/staff in the affected spaces, this further negatively impacts their productivity/performance and general teaching effectiveness.
What systematic challenges or issues does this example elucidate? Because of the general lack of local expertise, high tech systems, such as the ground source heat pump (GSHP) system, Solatubes/lighting control system and PV system used at this school typically require importing installation, operational and maintenance expertise from metropolitan areas of the state, increasing the cost and time required to maintain them. As a result, for this particularly rural New Mexico school, they must bring people in from Albuquerque or El Paso to help maintain these systems; at a minimum for small things they often have to get on the phone. It’s frustrating for these smaller, rural districts.
Often such systems in these contexts end up operating below design expectations long term, negatively impacting occupant productivity/performance and health, saving no energy, or worse, using more energy than had the system not been included. At some point they often end up being disabled. This gives high performance, sustainability, green, and/or associated certification systems a bad name – with the teachers/staff and students, as well as the community at large. And they’re less likely to incorporate such elements or similar elements in future projects.
What are the lessons learned? Three basic lessons:
- Studies have shown that manual-on/auto-off control (vacancy) is more effective at saving energy compared to auto-on/auto-off control (occupancy) for “occupancy sensors.” Delayed-on and false-on occurrences are reduced, reducing energy consumption, potentially extending lamp life and usually creating less problems and more effective control for the occupants.
- Commissioning, commissioning, commissioning: Commissioning, including enhanced commissioning, of all the building’s major systems will typically pay for itself multiple times over. This is certainly the case if productivity and O&M cost impacts are estimated quantitatively and included in any LCCA performed. It is important that the designers and contractors (if involved early on) communicate this clearly to the owner.
- Engagement, engagement, engagement: It is imperative that the O&M tasks and costs associated with the operation and maintenance of high tech systems be thought out ahead of time during programming/early design, particularly relative to an owner’s (and community’s) capabilities to determine if the owner lacks the needed expertise and resources. If so, then either a) a path is developed to provide the owner with the necessary expertise and resources through training, systems manuals, a formal building operating plan, maintenance contracts, adequate warranty periods, devoted percentages of operating budgets, etc., or b) alternative design strategies need to be considered that meet owner expertise and resources, save the intended amount of energy and provide high quality environments (learning environments in this case). The school, district and community must be engaged through charrettes, focus groups, surveys, interviews and observations to help determine if a) or b) is the best fit with the district’s and community’s values and goals (short and long term). The process will also likely involve “syncing” the values/goals of these various key stakeholder groups.