Multifamily buildings are the condominiums and apartments where we live and play. And, with the ongoing Covid-19 pandemic and the work-from-home movement, where we work too. The energy and water demand from occupant living and working (cooking, laundry, screen time) gives multifamily buildings unique energy and water profiles.
There are big opportunities to improve efficiency in multifamily buildings. The American Council for an Energy-Efficient Economy (ACEEE) believes the multifamily building stock can increase their efficiency by 15-30%, a $3.4 billion savings in the U.S. alone.
Energy and water efficiency does not only come with financial and environmental benefits. Improved occupant comfort and health and higher rental incomes are correlated with higher efficiency, more sustainable multifamily buildings.
When considering options to reduce energy and water use in multifamily buildings, no-cost or low-cost operations and maintenance (O&M) measures are good starting points. These measures are detailed in the first table, below.
Once building systems are functioning properly, deeper retrofit measures can be considered by deploying the following, ordered strategy:
Table 1: No-cost and low-cost energy and water conservation measures for multifamily buildings
|Measure Type||Measure Name||Measure Description|
|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.|
|Electric Load||Add timers to AC-DC elevator motors||Older buildings (built in the 1980s, 90s), may be equipped with AC-DC motors. Add or repair damaged timers on AC-DC elevator motor converters to prevent continuous running.|
|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||Repair leaky faucets||Repairing leaky faucets reduces water waste.|
|Domestic Hot Water||Ensure proper boiler combustion efficiency||Conduct a combustion analysis and a carbon monoxide test at least once a year to ensure efficiency and safety|
|Domestic Hot Water||Lower Domestic Hot Water (DHW) temperature set point||Reduce DHW set-points temperatures if currently set at 136.5℉ or higher. Reducing temperature setpoints decreases heating needs.|
|Envelope||Replace damaged door weatherstripping||Replace damaged weatherstripping and eliminate drafts on exterior, unit, and hallways doors.|
|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.|
|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.|
|HVAC||Reduce corridor thermostats||Corridor thermostats do not need to be kept to the same temperature as suites. Corridor thermostats can usually be set to 16-18℃ without sacrificing occupant comfort.|
|HVAC||Install extended surface area air filter||If both pre- and final filters are utilized in the HVAC system, replacing both with an extended surface area filter can help the system run more efficiently.|
|HVAC||Repair leaky ductwork||Repair ductwork leaks to ensure the HVAC system is operating efficiently.|
|HVAC||Calibrate HVAC air and water sensors||Building operators should ensure the sensors (e.g., temperature, humidity, pressure, flow) 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.|
|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 a chiller and cooling tower system, 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||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.|
After O&M measures have been addressed in multifamily buildings and existing systems have been confirmed to be operating properly, retrofit measures can be considered to reduce energy and water use and cost; from low-flow faucet installations to window replacement to appliance upgrades.
Capital investment, annual savings, payback period, available project funding, and project net present value are financial considerations when narrowing down the right measures for your building.
Retrofit measures are presented in the following table.
Table 2: Deeper energy and water conservation measures for multifamily buildings
|Measure Type||Measure Name||Measure Description|
|Domestic Water||Install low-flow faucets, showerheads, and dual-flush toilets||Installing low-flow faucets, showerheads and dual flush toilets in suites and common areas can reduce the amount of water used during day-to-day occupant life without impacting the occupant’s experience.|
|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.
Common areas and offices can be a good starting point. When access permits, in-suite lighting upgrades can be considered.
|Lighting||Install occupancy sensors||Install occupancy sensors in transient areas such as gyms and common areas 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. Both common area and in-suite opportunities may exist.|
|Lighting||Exterior Lighting Retrofit||Retrofitting exterior lights with newer, efficient lighting technology can have a meaningful impact on electricity usage.|
|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 common area 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 within suites and business centers. Ensure large TVs in common areas are turned off when not in use.|
|Plug Load||Purchase energy-efficient appliances and equipment||Replace aging or end-of-life appliances and equipment in common areas and suites with energy-efficient models (fridges, stoves, common area monitors, 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 main source of energy leakage. Adding to, or replacing roof insulation will help reduce energy needs. Can be most economical at the time of roof 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/or widen deadband zone.||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 has changed and no longer aligns with the existing HVAC system, a full HVAC replacement with the latest technology will have a drastic impact on building efficiency.|
|Domestic Hot Water||Add VFD to water circulation pump||A VFD can be added to a water circulation pump to increase the efficiency at part load conditions.|
|HVAC||Add VFD to chiller compressor||The chiller can operate more efficiently at part load conditions when its compressor is equipped with a VFD|
|HVAC||Replace boiler with condensing boiler||Condensing boilers are an energy-efficient upgrade and should be considered when replacing a boiler.|
|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.|
The Efficiate Utility Information System informs multifamily building operators about their energy and water use performance. Our insights help operators navigate towards more efficient buildings that reduce costs and increase customer health and comfort.