Blog Post

Night Surveys: The Lights Are On, But Nobody is Home

How Yale University's energy manager uses after-hours walk-throughs to save energy

Slideshow (click to launch)

This is the graphic that Julie Paquette uses to introduce and explain her approach to night surveys.

Graphic by Julie Paquette

Julie Paquette has been Director of Energy Management at Yale University for about 6 years. That means the buck stops at Paquette’s desk for the energy consumption of over 400 buildings on campus. Yale has a pretty sophisticated approach to energy, including the Yale Facilities Energy Explorer, an energy dashboard system that shows energy consumption and details for every one of those 400 Yale buildings.

But as a practicing engineer, Paquette recognizes the benefits of less sophisticated approaches to understanding building energy consumption, including “night surveys.” Armed with just a digital infrared thermometer (DIT) and maybe a dozen pages of recent reports (energy consumption, building’s controls schedule, and even the custodial schedule), Paquette walks her buildings with the members of the facility staff working in that particular building. They do this after the building is technically “closed” for the day. In the last four years, Paquette has “night-surveyed” more than 35 Yale buildings, from labs to museums to classroom buildings.

This past October my Yale Forestry and Environmental Studies graduate students joined Paquette’s team to survey Hendrie Hall. Hendrie Hall, shared by the School of Music and just about all of the Yale performing ensembles, recently went through a two-year extensive renovation and addition, completed around the start of 2017. So this night survey was checking up on how the building is measuring up over the last nine months or so compared to energy performance predictions.

“Tonight we’ll be focused on how we use this building,” Paquette says. “There are always ways to learn more about energy use and how we might adapt that use.” Paquette places the night survey in context with a simple graphic (see Image 1).


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Infrared thermometer checks

As we walk Hendrie Hall, starting about 10 p.m., my students are snapping photos of spaces. One student is reinforcing Paquette’s DIT shots with infrared camera shots.

It becomes pretty clear that quite a bit of energy is being wasted. From the official Yale Energy Management Hendrie Hall report:

  • General hallway and lobby lighting is higher than needed, especially in the evening hours. Operationally, lower level lights would be helpful to signify that the building is closing.
  • Lutron system can be reprogrammed to set back public lighting.
  • Replace row of PAR 38 Halogens in student lounge with LED type (see Images #2 and #3,below).
  • Individual offices had sporadic computer screens left on and printers left on.
  • AV systems left on in all larger spaces. Need to work with Yale AV staff to put into sleep / hibernate mode (see Images #4 and #5).
  • Air handling units were operating during walk-through past scheduled operating hours. Investigate programming and space condition trending. Initial assumption is that air handling units are operating because of humidity setpoints.
  • Band and glee rooms are used sporadically during the day and primarily in the evenings for rehearsal. Investigate appropriate schedule changes.

Reprogramming the controls

Not more than a couple of weeks after our Hendrie Hall night survey, Paquette sent me a graph (see Image #6), saying, “After the survey, we met again with Tara Deming and our electrical supervisor Ed Grund [Hendrie Hall Facilities staff] to review lighting schedules in the public corridors and front foyer. We reprogrammed the Lutron system to better reflect building use – and have saved approximately 100 kWh/day (the equivalent of three Connecticut homes.) We are following up on a number of additional items.” When I asked Paquette just what sort of return on investment there has been for her night survey, she said that night surveys are a key component to building energy project portfolios that offer simple payback periods less than 5 years and significant cumulative long term savings. Opportunities found at night are among the lowest cost, highest value carbon abatement strategies. Paquette concluded: “The Night Surveys work.”

Sometimes it’s the simple stuff that works best, especially if someone is taking responsibility for building performance over time. Someone like Paquette, just walking her Yale buildings at night.

Published January 8, 2018

Yost, P. (2018, January 8). Night Surveys: The Lights Are On, But Nobody is Home. Retrieved from

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February 6, 2018 - 3:12 pm

Thanks for this article as it lays a frame work and sets in a precedence for what we can do at our agency to emulate what you all have done to reduce our energy consumption. Spot on.