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Find Out How Your Building Uses Energy at Night

November 4, 2014 | 9 comments

Looking for a good way to see whether your energy-efficiency projects and building equipment are working like they should be? Try taking a walk through your building at night.

A commercial building is typically only occupied for eight or nine hours each workday, leaving 15-16 hours unoccupied. Although remote monitoring is helpful when it comes to keeping tabs on after-hours operations, it can be difficult for facilities managers to know how buildings are truly operating during the hours when no one is inside.

We may assume that HVAC, lighting, and building automation controls are working as intended, but even just one malfunctioning component can impact the entire facility. Periodic evening building tours – essentially serving as simple energy audits performed at night – can help uncover operational issues that affect building performance, energy efficiency, and water conservation.

According to BetterBricks, an initiative of the Northwest Energy Efficiency Alliance, night walks should be conducted with at least two staff members (including the facilities manager and building engineer or another member of the onsite property team). Depending on building size, several team members may be needed to evaluate possible energy waste and other issues.

Tours should be scheduled during times when the building is unoccupied. To get a better overall sense of the building’s operation, night walks can be scheduled at various intervals (a weekend afternoon, a weekend morning, a weeknight early in the evening, a weeknight late in the evening, etc.).

BetterBricks also recommends taking advantage of after-hours emergency calls. If you have to visit the building to address an equipment malfunction, take some time to walk through the rest of the building while you’re already there.

Here are some of the items you should be monitoring during a night audit:

  • Air movement, extreme temperature fluctuations, and humidity levels
  • Vibrations, humming, rattling, and other mechanical noises coming from HVAC, lighting, etc.
  • Electrical and mechanical system temperatures
  • Office equipment left on
  • Overly lit areas both inside and around the building
  • Dark areas both inside and around the building
  • Condensation around HVAC systems
  • Air diffusers blocked by furniture
  • Water spots, standing water, or dripping water
  • Odors (mold, overheating electrical equipment, chemicals, etc.)

Taking a closer look at your building after-hours may also help you pinpoint areas for security improvement. In the evening hours, it will be easier to spot under-lit areas. You’ll also be able to test access control and surveillance equipment to make sure appropriate entrances are secure, and that cameras provide enough visual detail in the evening hours.

Have you conducted a night walk or night energy audit? What did you uncover by walking through your building when it was unoccupied?


  1. Jim Newman
    November 8, 2014

    These are all excellent suggestions, all of which we look for when we perform energy audits for our clients.

    Many of them, of course, can be seen during normal working hours if the facility manager, building engineer or maintenance staff have the time to go looking for them.

    One point which might be expanded is no. 4, the one relative to office equipment left on. Sometimes it is difficult to tell whether computers are left on, as most of today’s computers will go into a Sleep cycle after a certain period of time – or whether a heater under a desk is on because you may not see or hear it – or it might not be running at that particular point in time.

    And, of course, there are the ever-present chargers for cell phones, i-Pods or i-Pads, MP3 players, etc. that most people leave on all night.

    The EPA says that these plug loads, also referred to as parasitic loads, can be as much as 15-20% of a commercial building’s electric load, and I’ve seen comments that say as much as 30% which, I do have to say, seems a bit out of line.

    One of the key problems with many buildings is that the facility personnel assume that their building automation system (BAS) or building management system (BMS) is properly taking care of everything. As this blog points out, this is not always the case. Why not? Because many of these systems do not have feedback loops that tell them when something is not functioning properly, so if the BAS or BMS says a HVAC system is turned off, then the operator assumes that to be the case.

    Night audits can save a lot of energy and a lot of money for a building owner. If a facilities team performed them once a month, the building owner would most likely save considerably more than the extra cost of the monthly walkthrough.

  2. Vista
    November 11, 2014

    Jim, thank you for your feedback! We’ve heard similar stats about plug loads – and that plug loads will continue to be a bigger part of energy use as buildings become more efficient (and HVAC and lighting energy use goes down as a result).

  3. Scott Ringlein
    November 13, 2014

    Agreed Jim!

  4. Susan Hirst
    March 24, 2015

    The company I work for is concerned about how much energy their building uses, especially at night. I’m sure they would be interested in hiring an energy auditing service to tour the building. I’ll have to suggest this to my boss.

  5. Vista
    March 25, 2015

    Hi Susan, glad you found some helpful advice in our blog. Good luck with reducing your building’s energy consumption!

  6. Great suggestions. Plug loads are energy drains when not in use, overnight, and weekends for desktop workstations, monitors, printers, large copiers, fax machines, data centers, and other equipment and devices. Keep in mind that while a work week may be just 40 hours, equipment is plugged in and using energy 168 hours a week.

    Upgrading old technology to to more energy efficient units is helpful, as are timers and powering down non-vital units when not in use. However the flip side is that relying on the ongoing cooperation of many individual staff members to be observant of energy efficiency practices is difficult and could be inconsistent.

    For an overall larger reduction in energy that works effortlessly and consistently, we found our Kilowatt Hours and Kilowatt Demand dropped dramatically after we did an LED lighting and solar power upgrade to our own building. Our savings from that as a whole have been exciting and impressive(we share our actual before & after bill data on our website to anyone interested). From here, upgrading our bigger energy hog equipment and controls will just further reduce our usage.

  7. Vista
    May 22, 2015

    Thanks for the feedback! We’ll be sure to check out your website to see the before/after data.

  8. Brad weaver
    June 2, 2015

    I (Northwest Energy Consulting) developed the Nightwalk program for NEEA, that is me in the Nightwalk videos as part of the Kilowatt Crackdown Program. . I also developed the existing building diagnostic tolls on the BB website.
    Nice that you are promoting the process!

  9. Vista
    June 8, 2015

    Hi Brad, we are familiar with you and your work! We’re happy to help you promote what we think is a great idea. Thanks for checking in!

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