Energy Saving Plan: Consider Occupant Comfort

May 29, 2018

Energy conservation strategies are only successful if they reduce building energy use without sacrificing end-user comfort, IAQ or other aspects of the building’s original design intent.

On the surface, it all looked great. The commercial high-rise facility’s energy program appeared to be a success: the cost savings were impressive, the energy savings promising. Three years of utility data proved what the facilities management team had already explained – they had implemented an energy management system in their existing facility. Everyone was satisfied.

The executives upstairs were happy with the reduced operations and utility costs. The sustainability team was happy to say they’d done their part to combat climate change and reduce strain on the New York City electric grid.

Ryan Lean, Director of Commissioning at Jaros, Baum & Bolles (JB&B) and Partner-in-Charge on the project, noted, “Everything looked fine at first glance. When we took a closer look at the building’s energy management program, we noticed a series of shortcuts that, while allowing the building to meet its energy reduction goals, didn’t give much consideration to the impact on occupant comfort or the operation of other building systems.”

[Related: Help For Your Building’s Energy Profile]

Energy Savings Don’t Always Meet Intent

Energy conservation in existing buildings is a popular topic. Local and federal legislation implemented in the past 10-15 years has been successful in raising awareness and targeting major large-square-footage, publicly owned facilities and multistory residential energy offenders.

Voluntary sustainability programs, including LEED and WELL, have furthered the cause for reduced energy consumption with programs tailored for the existing-building market. This has resulted in facility management teams starting to develop portfolio-wide energy management programs to meet legislative requirements and improve building marketability.

While this movement to drive down energy usage from the existing built environment is a step in the right direction, program roll-outs don’t always meet their intent. Ultimately, energy reduction strategies are only successful if they reduce building energy use without sacrificing end-user comfort, IAQ or other aspects of the building’s original design intent.

Energy Efficiency in Existing Buildings

Reducing energy and carbon emissions in existing buildings can’t be overstated.

The report One City: Built to Last from the New York City Mayor’s Office of Sustainability estimates that the energy we use in our homes, schools, workplaces, stores and public facilities amounts to about 75% of our contribution to climate change. Of that 75%, a majority of energy use comes from the existing-building stock. (By 2030, at least 85% of New York City’s buildings will be comprised of those already present today.) The effects of climate change will only get worse if immediate efforts aren’t made to reduce human impact on the environment.

That’s where New York City’s 80 x 50 plan comes into play: developed communities need to reduce greenhouse gas emissions by at least 80% by 2050. Considering the amount of energy consumed in our existing buildings, targeting this sector now can bring about meaningful change.

Case Study: Unintended Effects of Load Shedding Program

Considering the implications of climate change, it’s reasonable to ask whether an energy-saving measure can, regardless of its impact on other existing systems in the building, ever be a bad thing. Short answer: yes.

An energy-saving measure could be effective in driving down kilowatt hours, but it might also have negative side effects that outweigh the energy-related benefits. This was the case with the above-referenced project. The facility required existing-building commissioning services for New York City Local Law 87. The intent was to identify low- or no-cost measures to tune up equipment, reduce facility energy use and increase operating efficiencies.

During the project’s investigation phase, there was an opportunity to examine the finer details of the custom-built energy management system. After a few hours with the building management system service provider who had developed the program, it was clear that the main energy-saving component was a load shedding program.

Implementing load shedding makes sense because this type of program causes a deliberate stage-down of non-essential equipment in times of high electrical demand. In addition to reducing strain on the electrical system and minimizing costly demand charges, load shedding programs are a great way to reduce overall facility energy consumption.

[On topic: How School District Cut 62 Percent in Energy Spending]

As the project moved forward, the team began to see how the load shedding program actually affected overall facility operation. Functional testing revealed that the program didn’t just stage down nonessential equipment, it also staged down air handling units responsible for providing ventilation and temperature control to the building’s occupied floors.

The program was developed with a daily kW energy limit, and when the facility energy demand approached this limit, the program would automatically shed load by directly overriding air handling unit fan speed outputs. As a result, the variable air volume distribution systems on occupied floors were consistently unable to maintain duct static pressure set points, leading to poor air distribution and general occupant discomfort.

While the load shedding program had been instrumental in saving energy up front, it disrupted the design intent of the original airside system and reduced the indoor environmental quality of spaces at the end of the air distribution system. In addition to temperature discomfort due to lack of proper air distribution, the quality of the air itself was compromised, thus increasing occupant health risk.

Energy Reduction: Part of a Holistic Plan

Addressing these issues is still a work in progress. Implementing a new energy management program is a challenge in older facilities that don’t have state-of-the-art equipment or a centralized building management system.

As existing-building management teams turn to engineers, architects, commissioning professionals, inspectors and sustainability consultants to review energy management programs, these reviews will require a balanced, unbiased perspective.

80 x 50 is an admirable goal, and it can be easy to view all energy-saving measures as beneficial to the building. In reality, though, energy reduction has to balance with other important building elements such as adequate airside or waterside distribution, IAQ and water quality, with a steady eye on occupant comfort and well-being.

Molly H. Dee, CEA, LEED GA, WELL AP, CPHC, is a senior project engineer in the commissioning services group of Jaros, Baum & Bolles (JB&B) of New York City.

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