Energy efficiency is no longer just the responsible thing to do. It’s now a necessity, and has become a major part of what facilities management entails.

As a result, the Northwest Energy Efficiency Alliance’s BetterBricks Initiative and the IFMA Foundation have joined forces to produce a practical, realworld guide for facility managers to be more energy efficient.

The “No-Cost/Low-Cost Energy Savings Guide” is the fifth in a sustainability series produced by the IFMA Foundation to provide facility personnel with the tools to get started identifying problem areas and implement no/low-cost solutions for immediate benefits.

The guide includes these top four energy saving opportunities:
• Equipment Scheduling: The first step of a no/low-cost strategy is to determine where energy is being wasted. Unoccupied areas should not have chillers and coolers running. Establishing where this waste takes place is step one.
• Sensor Error: Sensor settings are often out of sync and this section demonstrates what to look for, how to make changes and how to regularly schedule updates to monitor settings.
• Simultaneous Heating and Cooling: Excessive reheating uses unnecessary energy and if an HVAC system’s settings are out of sync, it forces the air handler to work harder. The guide provides information on how to tune-up these systems.
• Outside Air Usage: Optimum indoor air quality requires efficient ventilation and this can’t take place if dampers are stuck open or improperly calibrated. In the No-Cost/Low-Cost Energy Savings Guide, facility managers will find ways to cut energy costs just by maintaining this system.

Equipment Scheduling

Poor equipment scheduling has many negative impacts: Energy use increases proportionally to operating hours for most nonmodulating equipment such as lighting, plug loads and constant volume fans.

Ventilation or exhaust fans usually use more energy at night because the ventilation or makeup air is colder.

Staging equipment to reduce demand charges can actually increase energy costs. For example, some facilities may stage equipment over an hour or two to avoid demand spikes. The spike in current required to start motors does not last long enough to affect billing demand, typically measured over 15- or 30-minute intervals. The equipment comes online earlier than necessary, increasing consumption and having no effect on the demand charge.

Longer operating hours result in shorter equipment life and more frequent replacement of lamps, ballasts, filters, belts, electric heating coils, contactors, relays, motors, pumps, chillers, boilers, compressors and other equipment.

Increased operating hours of a building increases the cleaning frequency for chiller bundles, boiler tubes, fan coils, evaporator coils and condenser coils.

Walking through the building when it is unoccupied is a good first step in identifying unnecessary equipment operation. If equipment is running, look for a reason. It is usually obvious that a lamp or printer should be off, but HVAC equipment may be running to supply a computer room that needs continuous conditioning.

Sensor Error

Sensor error can increase energy use, compromise occupant comfort, and prevent plant and system loads from being met. This is most often caused by calibrated sensors that have not been calibrated. However, it can also be due to incorrectly placed sensors failed sensors or mistakes in control setup.

While building systems use many sensors, critical control sensors are the most likely to cause severe energy penalties. For example, while space temperature sensors result in energy waste and comfort problems, the effect on energy is usually minor and restricted to one zone. On the other hand, errors from a critical control sensor, such as the temperature of return air at the air-handling unit, can cause large energy penalties affecting many zones, yet may not cause comfort issues.

Sensor error is hard to detect unless the sensors are calibrated regularly. Wide varieties of sensor types are available for HVAC use. Many can be calibrated and others need to be replaced periodically. It is important to know the specifications of the specific sensor in order to maintain it.

Control sensors with the most potential to have a significant effect on energy use are generally those used to implement resets and control outside air at air handling units and central plants.

Critical control sensors include:
• Mixed air temperature sensor;
• Return air temperature sensor;
• Outside air temperature sensor;
• Supply air temperature sensor;
• Chilled water temperature sensor;
• Hot water temperature sensor;
• Carbon dioxide sensor; and
• Carbon monoxide sensor.

Simultaneous Heating and Cooling

Central fan systems are designed to supply space conditioning to multiple areas in a building. Each area has its own space conditioning needs. Typically a central fan supplies cool air to one or more zones. To meet the conditioning requirement of each zone, most central HVAC fan systems use some form of reheat. At the zone level, the quantity of air is usually modulated to satisfy the cooling load or may be reheated to meet a heating load.

A typical office building floor will have electric or hydronic coils installed in the ductwork or in the fan boxes serving the perimeter areas, while the central area is cooled. The temperature of the cool air leaving the air handler at the primary supply determines the amount of reheat required in the various zones. Control strategies optimize the supply air temperature and reduce reheat. Usually the supply air is reset to the highest temperature that can still meet the largest cooling load. If the control strategy is not optimized, the supply air will be cooler than necessary and reheating it will use more energy than necessary.

There are many variations of central HVAC fan systems that have similar problems of simultaneous heating and cooling. The following are systems that should be targeted for energy saving O&M opportunities:
• VAV systems with reheat;
• Constant volume systems with reheat;
• Dual duct systems;
• Multi-zone fans; and
• Central air conditioning systems with perimeter heating.

To determine if there are problems, generate a trend log for the system. Trend the following:
• Outside air temperature (OAT);
• Return air temperature (RAT);
• Mixed air temperature (MAT); and
• Supply air temperature (SAT).

Outside Air Usage

Outside air is supplied to a building by the ventilation system in order to displace indoor air pollutants and provide adequate ventilation for the building occupants. Proper ventilation rates are needed to maintain indoor air quality.

Building codes require a minimum ventilation rate, usually based on ASHRAE Standard 62: “Ventilation for Acceptable Indoor Air Quality.”

While buildings are only required to meet the ventilation code in effect at the time of construction or major remodel, it is good practice to provide ventilation that matches the most current codes and standards.

HVAC System is Capable

Requirements change from state to state and can usually be found by doing a search at the appropriate state Website on air quality building codes.

Many buildings use an outdoor air economizer, which uses outside air for free cooling when its temperature is below the return air temperature.

The economizer varies the outside air quantity from the minimum ventilation rate up to 100 percent outside air as needed to cool the building.

Energy codes generally require that outside air dampers be closed when the building is unoccupied, and open to the minimum ventilation rate when it is occupied and being heated. When the building requires cooling, the economizer activates and allows additional outside air when the outside air is cooler than the return air.

Demand controlled ventilation adjusts the amount of outside air based on the number of occupants in the space. It is best applied to areas with large variations in occupancy such as auditoriums, gymnasiums and large conference rooms. By adjusting the ventilation rate to meet actual, rather than peak occupancy, requirements, energy is saved while maintaining indoor air quality. To obtain a copy of the “No-Cost/Low- Cost Energy Savings Guide,” visit www.ifmafoundation.org or for other no-cost/low-cost strategies that can help you achieve significant operational savings, visit the BetterBricks Website at www.betterbricks.com/operations. The guide and resources on both Websites are downloadable free of charge. ❑