Heating, Ventilation and Air Conditioning (HVAC) is responsible for a significant proportion (around 35%) of a building's total energy consumption. Given the function it serves and the complexity the system has, if any of the parts wear out, it can result in a lot of pressure on other parts of the system, resulting into a higher energy consumption, utility costs and serious global impacts. Thus, replacing it with more efficient systems and maintaining it regularly is of utmost importance.
Recommendations provided:
High-Performance Upgrades
High-Performance Upgrades
New high-performance HVAC equipment have higher ratings for seasonal energy efficiency ratios (SEER), energy efficiency ratios (EER), Coefficient of performance (COP) or heating seasonal performance factors (HSPF) than conventional equipment. In addition to high efficiency ratings, high-performance HVAC equipment are coupled with efficient ventilation systems and controls. The installation and proper use of high-performance HVAC systems can result in considerable energy, emissions, and cost savings.
For maximum performance, a dedicated outdoor air system (DOAS) is recommended when installing one of the systems below. A DOAS reduces energy use by decoupling the dehumidification and conditioning of ventilation air from sensible cooling (e.g. resulting from solar heat gain or electric equipment in the space) and heating in the zone. The outdoor air is conditioned by a separate DOAS that is designed to dehumidify the outdoor and to deliver it dry enough (i.e., with a low enough dew point) to offset space latent loads (resulting from moisture and humidity), thus providing space humidity control.
Asset Score Report Recommendations:
1. Replace existing HVAC system with a Packaged Rooftop Heat Pump and a Dedicated Outdoor Air System (DOAS) for ventilation
Cost: $$-$$$
Image 1: Packaged Rooftop Heat Pump (Source: Berkeley Lab)
The heat pump systems recommended here by the refers to air-source heat pump systems. Electric air-source heat pumps use the difference between outdoor air temperatures and indoor air temperatures to cool and heat conditioned spaces. Packaged rooftop heat pumps include the evaporator coil, condenser, and compressor assembled as a single package and mounted on a roof.
These units have become more efficient (higher SEER and HSPF) and replacing older units with the current state-of-the-art unit can provide significant savings.
2. Replace existing HVAC system with a Variable Refrigerant Flow (VRF) system and Dedicated Outdoor Air System (DOAS) for ventilation
Cost: $$-$$$
Image 2: A Variable Refrigerant Flow (VRF) system (Source: Berkeley Lab)
Variable Refrigerant Flow (VRF) systems use a variable-speed compressor to modulate refrigerant flow for efficient heating and cooling in buildings. Unlike traditional systems, VRF operates continuously for longer periods, adjusting refrigerant flow to maintain a stable room temperature since the compressor doesn't need to cycle on and off. The required refrigerant flow is supplied directly to indoor fan coils in multiple individual units instead of moving conditioned air through the ductwork, minimizing energy losses associated with it in traditional systems. Once the set point is reached, the refrigerant flow is adjusted to maintain the room temperature smoothly without fluctuation.
VRF systems paired up with DOAS provide an energy-efficient approach that optimizes compressor speed, matching system output to the building's load as closely as possible without compromising a space's thermal comfort.
3. Replace existing HVAC system with a Water Loop Heat Pump (WLHP) and Dedicated Outdoor Air System (DOAS) for ventilation
Cost: $$-$$$
Image 3: A Water Loop Heat Pump (WLHP) (Source: Berkeley Lab)
Water loop (or water-source) heat pump systems deliver high-performance heating and cooling with exceptional efficiency. These systems include a closed water loop which provides condenser water to interior zone cooling units, picking up the heat normally rejected to a cooling tower, and transfers it as the heat source (evaporator load) for perimeter zone heat pumps. In scenarios where the heat pump system provides heating, supplementary heat is provided by a boiler to the condenser water loop. This setup substantially increases the coefficient of performance (COP) and lowers the operating cost of the heat pumps over conventional air-source heat pumps.
Like-to-like Upgrades
A variety of HVAC system upgrades can be considered, depending on the existing configuration. Both equipment replacements and add-on technologies can improve the efficiency of HVAC systems. Some equipment recommendations may suggest implementing the same type of equipment or technology. This implies installing a newer high efficiency version of the current technology. When a “High Efficiency” unit is not specified in an AS report, that unit may not be cost effective. However, it is recommended to consider installing the highest efficiency level when economically feasible.
Asset Score Report Recommendations:
1. Upgrade to High-Efficiency Boiler
Cost: $$$
Image 4: A graphical representation of a Boiler (Source: Berkeley Lab)
A boiler is a heating system that produces steam or hot water by burning a fuel such as oil or natural gas, to heat a building. On the other hand, a furnace creates hot air that moves through air vents and ducts to provide heating. The three main components of a boiler are the burner, combustion chamber and heat exchanger.
Most new and modern boilers are more efficient and are in a better operating condition than a decades-old boiler. While older fossil fuel and boiler systems have efficiencies in the range of 56% to 70%, the newer heating systems can reach up to around 98.3% efficiency. When upgrading to new conventional fossil fuel or natural gas furnaces (in buildings with air based heating systems) or boilers (in buildings with water-based heating systems), installing the highest efficiency level that is economically feasible must be considered to achieve highest energy savings. High-efficiency fossil fuel or natural gas furnaces and boilers refer to condensing type units (around 10% - 12% more efficient than equivalent non-condensing boilers) and can greatly reduce heating bills.
Image 5 displays the Federal Energy Management Program (FEMP) designated efficiency requirements for large commercial boilers.
Image 5: Efficiency Requirements for Large Commercial Boilers (Source: FEMP 2022)
Resources:
- https://www.energy.gov/energysaver/furnaces-and-boilers
- https://www.energy.gov/femp/purchasing-energy-efficient-large-commercial-boilers
- https://www.energy.gov/femp/purchasing-energy-efficient-small-commercial-boilers
2. Upgrade to High-Efficiency Chiller
Cost: $$$
Image 6: A graphical representation of a Chiller (Source: Berkeley Lab)
A chiller is an equipment that removes heat by circulating a heat-absorbing refrigerant through a series of mechanisms such as vapor-compression, adsorption refrigeration, or absorption refrigeration cycle. A chiller consists of various components such as a condenser, compressor, evaporator, expansion valves, power unit, control unit, water boxes.
Chilled water systems are commonly installed in large buildings (more than 100,000 square feet) and consume a large amount of energy; therefore, efficiency improvements can produce significant savings. Newer chillers have more advanced compressors and automatic controls, often allowing a significant reduction of energy expenses. While such systems are complex and provide several upgrade opportunities, an integrated approach to upgrades is necessary to ensure that individual components are compatible with overall system efficiency improvements.
Recommendations include upgrading to a higher efficiency chiller of a different type (e.g., from a reciprocating type chiller to a screw or scroll type) or to a new chiller of the same type that improves performance compared to the existing chiller. Specific considerations will vary according to current system configuration, cooling load magnitude, full- vs. part-load operation needs, and potential staging requirements. Image 7 and 8 provide general guidelines for selecting water and air-cooled chillers.
Image 7: Efficiency Requirements for water-cooled electric chillers (Source: Berkeley Lab 2022) 
Image 8: Efficiency Requirements for air-cooled electric chillers (Source: FEMP 2022)
Resources:
- https://www.energy.gov/femp/purchasing-energy-efficient-water-cooled-electric-chillers
- https://www.energy.gov/femp/purchasing-energy-efficient-air-cooled-electric-chillers
3. High Efficiency PTAC Replacement
Cost: $$ (Review)
Image 9: A Packaged Terminal Air Conditioner (PTAC) (Source: Berkeley Lab)
A Packaged Terminal Air Conditioner (PTAC) is a self-contained heating and air conditioning unit installed directly through a wall to serve a single zone. It is typically used in offices and hotels where multiple units are purchased together saving a lot of installation cost and time (given it's a single unit and does not need refrigeration lines). A PTAC unit consists of a compressor, a heat exchanger coil and a blower all in a single case.
PTACs have evolved over time and their Energy Efficiency Ratio (EER) has improved. Higher EER implies higher efficiency of the system. Thus, upgrading to the current state-of-the-art equipment often yields energy savings. According to ASHRAE 90.1 2022, the minimum efficiency for a standard size PTAC (for cooling mode) is 9.5 EER for size greater than 15,000 Btu/h.
4. High Efficiency PTHP Replacement
Cost: $$ - $$$
Image 10: A Packaged Terminal Heat Pump (PTHP) (Source: Berkeley Lab)
A Packaged Terminal Heat Pump (PTHP) is a PTAC capable of using the refrigerating system in a reverse cycle or heat pump mode to provide heat. It typically consists of a compressor and two copper or aluminum coils with fins to aid heat transfer.
The heat pump systems recommended here in the asset score tool refer to air-source heat pump systems. New air-source heat pumps achieve enhanced efficiency and performance through advancements like thermostatic expansion valves for precise refrigerant flow control, variable speed blowers that compensate for duct issues, improved coil design, and enhanced electric motor and compressor designs, along with copper tubing featuring grooved interiors for increased surface area. Thus, upgrading to the current state-of-the-art equipment can yield energy savings.
Some general tips or guidance, as per FEMP, for selecting heat pump systems include looking for the ENERGY STAR label and selecting the heat pump based on the climate of the location. Heating efficiency for air-source heat pumps is indicated by the heating season performance factor (HSPF) which should be given more importance in colder climates. Cooling efficiency indicated by Seasonal Energy Efficiency Ratio (SEER) should be prioritized in warmer climates. In some situations (e.g., in Climate Zones 1 and 2), it may be more cost-effective to use electric resistance heat in lieu of a heating system that uses a central furnace or boiler.
According to ASHRAE 90.1 2022, the minimum efficiency for a standard size PTHP (for cooling mode) is 9.5 EER for size greater than 15,000 Btu/h.
Resources:
5. High Efficiency Rooftop AC Replacement
Cost: $$-$$$
Image 11: Packaged Rooftop Air Conditioner (Source: Berkeley Lab)
Rooftop AC units are self-contained systems, installed on the roof of a building, that house all the components necessary for air conditioning in a single unit. These components typically include a compressor, condenser, evaporator, fans, and sometimes a heating element for year-round climate control. The units are designed to be compact, making efficient use of rooftop space.
Newer units often have higher SEER (Seasonal Energy Efficiency Ratio) ratings, indicating better energy efficiency and reduced energy consumption compared to older models. Thus, upgrading to the current state-of-the-art equipment often yields energy savings.
Resources:
6. High Efficiency Rooftop Heat Pump Replacement
Cost: $$-$$$
Image 12: Packaged Rooftop Heat Pump (Source: Berkeley Lab)
Similar to a rooftop AC, a rooftop heat pump is a self-contained system placed on the rooftop with both the evaporator as well as the condenser coils along with other parts packaged into a single unit. The only difference is that a heat pump can provide both heating and cooling. These systems are typically placed on the rooftops in buildings that have space and easy access to the roof.
Heat pumps have improved throughout the years and newer models are more efficient. Thus, upgrading to the current state-of-the-art equipment often yields energy savings.
7. High Efficiency WLHP Replacement
Cost: $$-$$$
Image 13: A Water Loop Heat Pump (WLHP) (Source: Berkeley Lab)
Unlike traditional air-source heat pumps that exchange heat with the outdoor air, water-source (or water loop) heat pumps transfer heat to or from a water loop, which is a closed-loop system circulating water between the heat pump units and a central plant or water source.
As technology advances and sustainability becomes a more significant focus, Water Loop Heat Pumps (WLHP) continue to evolve, offering greater energy efficiency and environmental benefits. Thus, upgrading to the current state-of-the-art equipment can often yield energy savings.