Offices represent approximately 20% of the U.S. and Canadian commercial building stock. As the average building wastes 30% of its energy, office buildings contribute to the building inefficiency conundrum.
Heating, ventilation, and air conditioning (HVAC), and lighting, can make up 75% of energy use in offices. As such, when considering energy efficiency opportunities, these areas can be given attention first.
There are opportunities for energy and cost savings in these buildings through operations and maintenance (O&M), sometimes referred to as existing building commissioning (EBCx). Because of the complexity of building energy systems, a small issue in the system can have a large impact on energy use. As such, EBCx can reduce energy use by 20% or more. Below are common EBCx measures that can be implemented at no-cost or low-cost by the building’s O&M team.
Table 1: No-cost and low-cost energy and water conservation measures for offices
|Measure Type||Measure Name
|Lighting||Exterior light scheduling using photocell sensors||Use a photocell sensor(s) to turn exterior building lights on and off 30 to 60 minutes after sunset and before sunrise, respectively. Photocells detect sunrise and sunset more accurately than clock-based timers, reducing lighting waste.|
|Lighting||Install LEDs in exit signs||Since they run 24/7, install LEDs in exit signs to maximize their efficiency.|
|Envelope||Replace damaged door weatherstripping||Especially on exterior doors, replace damaged weatherstripping and ensure drafts are eliminated.|
|Envelope||Eliminate Leakage||Use an infrared camera to identify and remedy building energy leak points. As-built drawings can also help in the leakage identification process.|
|HVAC||Repair leaky ductwork||Repair ductwork leaks to ensure the HVAC system is operating efficiently with no duct leakage.|
|HVAC||Calibrate HVAC air and water sensors||Building operators should ensure the sensors (e.g., temperature, humidity, pressure, flow sensors) that optimize building heating and cooling are calibrated periodically to ensure proper function.|
|HVAC||Reset supply air-temperature setpoint||This feature of an HVAC system allows the air temperature supplied to the building’s zones (rooms) to be adjusted automatically to the zone’s needs, rather than supplying at a constant air temperature. This increases efficiency.|
|HVAC||Eliminate unneeded HVAC processes during unoccupied periods||If the HVAC can be turned off during unoccupied periods, do it! Outside air dampers should be closed as well. Reducing runtime is one biggest “bang for your buck” opportunities to increase efficiency and reduce cost.|
|HVAC||Economizer Maintenance||When outside temperatures permit, make sure economizers are functional and utilize outside air temperatures in meeting building heating and cooling loads. This is a good step to reduce unneeded mechanical heating or cooling.|
|HVAC||Chiller and cooling tower maintenance||For buildings with chiller and cooling tower systems, regular maintenance, including cleaning, will ensure the system is operating at peak efficiency.|
|HVAC||Inspect and repair damaged pipe insulation||Make sure the heating and cooling system piping system, including the domestic hot water loop, is properly insulated. This measure ensures maintenance staff safety as well as maximizes system efficiency.|
|HVAC||Chilled water temperature reset||During periods of low cooling load needs, increase the setpoint of the water chiller to increase efficiency.|
|HVAC / Lighting||Implement a custodial daytime schedule||Move custodial staff to daytime hours so HVAC and lighting systems can enter “building unoccupied mode” sooner and reduce energy use in the evenings.|
|HVAC||Clean heating and cooling coils and fins||In the air handling unit (AHU), clean the heating and cooling exchanger’s coils and fins to maximize efficiency.|
|HVAC||Correct refrigerant charge||In refrigerant-reliant heating and cooling systems, ensure the refrigerant charge level is at optimal levels.|
|HVAC||Adopt a regular HVAC schedule||HVAC systems should be inspected and adjusted twice a year to ensure proper functioning. In cold climates, this can be done before the winter and summer seasons.|
|Water Use||Adopt water-friendly landscaping||Landscaping with plants having low water needs (such as native plants) can reduce the outdoor water use on your property.|
|Education / Training||Employee education and training||This measure involves energy and water conservation awareness and training for employees and building visitors as well. Empowering and engaging employees can go a long way in your efficiency improvement goals.|
More extensive retrofit measures can be pursued in office buildings to increase energy savings even further. It is not uncommon for these measures, in combination with EBCx measures, to push energy savings above 40%.
A lighting retrofit is one measure for a building operator to consider. Lighting standards are guided by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) Standard 90.1. Based on the 2019 standard’s building area method, offices are now guided towards a 0.64 watts per square foot (watts/sq.ft) light power density (LPD). This density could be considered as a target when upgrading existing building lighting systems.
Retrofit measures typically require higher capital investments, but paybacks less than 10 years are not uncommon. The table below outlines office retrofit measures.
Table 2: Deeper energy and water conservation measures for offices
|Measure Type||Measure Name||Measure Description|
|Lighting||Interior lighting retrofit||There are different levels of lighting retrofits. A simple lighting retrofit involves light and ballast replacement with the latest LED technology. A deeper lighting retrofit is a broader lighting redesign that can include LPD and light placement optimization, daylight harvesting, and sensor controls.|
|Lighting||Install occupancy sensors||Install occupancy sensors in transient areas such as conference rooms to turn lights off when vacant. This reduces energy waste from “day-burning” lights that could be intentionally or accidentally left on.|
|Lighting||Add daylight harvesting||Implement daylight harvesting to leverage natural light. When daylight is sufficient to offset indoor lights, these indoor lights turn off automatically. This measure can be considered on its own or as part of a lighting retrofit.|
|Lighting||Exterior Lighting Retrofit||Retrofit exterior lights with newer, efficient models. Consider a lighting redesign that takes into account illumination needs and the latest technologies.|
|Plug Load||Install block heater timers||In cold climate tenant/occupant parking lots, cars may plug into block heat plug outlets for a whole day. Since cars only need 3 to 4 hours of heating per day, a block heater timer can be installed to reduce electric loads.|
|Plug Load||Add office equipment on/off controls||Add computer energy management software and use smart power strips to automatically turn off electronic equipment (computers, lights, etc.) when not in use.|
|Plug Load||Purchase energy-efficient office equipment||Replace aging or end-of-life equipment with rated energy efficiency equipment (computers, monitors, coffee makers, fridges, etc.)|
|Envelope||Replace windows||Update windows to current or emerging “net-zero” building codes. This can be done either before or at the existing windows’ end-of-life.|
|Envelope||Upgrade wall insulation||Update wall insulation to current or emerging “net-zero” building codes. This may be combined with other envelope initiatives such as window replacement.|
|Envelope||Add roof insulation||Roofs are a key source of energy loss. Add to, or replace the existing insulation to increase efficiency. This is most economic when the roof is due for replacement.|
|Envelope||Add a Vestibule||Vestibules isolate the inside environment from the outside environment during occupant entry. Vestibules prevent the loss of heated or cooled air from escaping when exterior doors open.|
|HVAC||Install deadband thermostats and set wide deadband||Usually, temperatures within a building’s zone remain comfortable between 20.6℃ (69℉) and 23.9℃ (75℉). Installing and setting deadband thermostats can maintain occupant cover while reducing HVAC heating and cooling.|
|HVAC||Reduce Minimum Airflow in VAV box||In variable-air-volume (VAV) HVAC systems, there may be an opportunity to reduce the minimum airflow when no heating or cooling is provided, saving energy.|
|HVAC||Replace Supply fan motor and equip with VFD or VSD||Supply fan motors have become more efficient over time and replacement can be considered even before the fan’s end-of-life. Variable frequency drives (VFDs) or variable speed drives (VSDs) enhance efficiency further by modulating motor speeds at part load conditions, increasing overall building efficiency.|
|HVAC||HVAC replacement||Whether the HVAC system is at its end-of-life or the building’s function requires wholesale changes to the HVAC system, a full replacement with the latest technology will have a drastic impact on building efficiency.|
|Water Use||Add VFD to water circulation pump||A VFD can be added to a water circulation pump to increase the efficiency at part load conditions.|
|Generation||Investigate onsite combined heat and power (CHP) opportunities||Depending on input fuels available in your area (natural gas, biomass, etc.), a CHP system can allow your building to produce its own heat and power, reducing energy grid reliance. Discussion with internal O&M teams is a good starting point followed by preliminary technical, economic, and regulatory analysis.|
|Generation||Investigate onsite solar generation opportunities||Depending on the solar potential in your area and the layout and solar readiness of your building, installing solar photovoltaic (PV) cells for onsite generation could help offset your reliance on grid power and the power bill. Discussion with internal O&M teams is a good starting point followed by preliminary technical, economic, and regulatory analysis.|
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