Energy Effiency

Whole-House Dehumidifiers and ERV/HRV Air Exchangers

Controlling humidity and providing fresh air are crucial for both health and energy savings.

• Whole-House Dehumidifiers: A high relative humidity (RH) level makes the air feel warmer and more stagnant. This causes occupants to set their air conditioners to a lower temperature to feel comfortable. A whole-house dehumidifier removes excess moisture from the air, allowing you to feel comfortable at a higher thermostat setting. By raising the AC setpoint by just a few degrees, you can save a significant amount of energy, as the AC system doesn't have to work as hard to cool a "heavier" load.

• Energy Recovery Ventilators (ERVs) and Heat Recovery Ventilators (HRVs): Modern, well-sealed homes are energy-efficient but can trap indoor air pollutants. ERV and HRV systems are designed to provide fresh outdoor air while simultaneously exhausting stale indoor air. They are highly efficient because they transfer the heat (and in ERVs, the moisture) from the outgoing air to the incoming air. This means the HVAC system doesn't have to spend a lot of energy re-heating or re-cooling the fresh air, which is a major benefit for both indoor air quality and the home's energy consumption.

HVAC System Cleaning

A clean HVAC system is an efficient HVAC system. When components are dirty, the system has to work much harder to move and condition air.

• Cleaning the Blower Wheel and Evaporator Coil: The blower wheel is the fan that moves air through the ductwork. When it's caked with dirt and grime, it can't move air efficiently, which puts a strain on the fan motor and wastes electricity. Similarly, the evaporator coil is where the refrigerant absorbs heat from the indoor air. When this coil is covered in a layer of dust and dirt, it loses its ability to transfer heat effectively, forcing the AC compressor to run longer and use more energy. Regular cleaning of these components ensures maximum airflow and optimal heat exchange, reducing energy consumption.

Correcting Problem Ductwork

The ductwork is the circulatory system of your HVAC. If it's compromised, your system's energy efficiency plummets.

• Leaking, Damaged, or Disconnected Ductwork: The U.S. Department of Energy estimates that up to 30% of conditioned air can be lost through leaks in the duct system. When this happens, the heated or cooled air never reaches its intended destination, forcing the HVAC system to run longer to achieve the desired temperature. By sealing ductwork leaks with mastic or metal-backed tape and repairing any damage, you ensure that the conditioned air is delivered where it's needed, improving both indoor air quality and energy efficiency. This not only lowers your energy bills but also reduces the strain on your HVAC system, extending its lifespan.

1. Energy Savings from Whole House Dehumidifiers (WHDs)

A WHD is an energy-saving appliance because it efficiently manages the latent load (moisture) independent of the main Air Conditioning (AC) system, which primarily manages the sensible load (temperature). This specialization reduces the energy consumed by the larger, less efficient AC unit.

1. Reduced AC Run Time

• The Latent Load Burden: A standard AC unit must expend significant energy condensing moisture out of the air before it can effectively lower the air temperature. In humid climates, up to 50% of an AC unit's total energy consumption is dedicated to moisture removal.

• WHD Specialization: The WHD actively and efficiently removes humidity, allowing the AC system to run for shorter cycles to meet the temperature setpoint. This decreases overall compressor run-time, leading to substantial electricity savings.

2. The Comfort Setback Strategy

• Lowering the Setpoint: Human comfort is determined by both temperature and humidity. Lowering the Relative Humidity (RH) below 60% makes the air feel cooler. For example, a setting of 78∘F at 50%RH can feel equivalent to 75∘F at 65%RH.

• Direct Energy Reduction: This allows the occupant to raise the thermostat setting (e.g., by 2∘F to 4∘F) without sacrificing comfort. Since every degree the thermostat is raised in summer can translate to an approximate 3% to 5% reduction in cooling energy, the WHD provides a direct pathway to lower utility bills.

2. Energy Savings from Energy/Heat Recovery Ventilators (ERVs/HRVs)

ERVs & HRVs are designed to meet fresh air ventilation requirements (necessary in tight, modern buildings) without the massive energy penalty of traditional ventilation (e.g., a simple exhaust fan).

The Principle of Energy Recovery

These devices are high-efficiency air-to-air heat exchangers that recover energy from the exhaust air stream and use it to pre-condition the incoming fresh air.

• HRV (Heat Recovery Ventilator) - Sensible Energy Savings: In winter, an HRV transfers heat from the warm, stale outgoing air to the cold, fresh incoming air. This can recover 70% to 90% of the heat energy, meaning the furnace or heat pump doesn't need to generate that heat, significantly reducing heating costs.

• ERV (Energy Recovery Ventilator) - Latent and Sensible Savings (Best for Humid Climates): An ERV transfers both heat (sensible energy) and moisture (latent energy). In the summer, it transfers heat and humidity from the hot, humid incoming air to the cool, dry outgoing air. This pre-conditions the fresh air before it reaches the main AC system, effectively lowering the latent load on the AC and complementing the WHD for maximum efficiency.

Energy Efficiency of Controlled Ventilation

• Avoiding Waste: Simple exhaust ventilation systems discard expensive conditioned air and replace it with unconditioned outdoor air, drastically increasing the energy load. ERVs & HRVs provide a controlled air exchange rate while recovering the thermal energy, ensuring that the energy used to heat or cool the indoor air is recycled, directly translating into lower energy bills for code-compliant fresh air.

1. Effect of a Dirty Evaporator Coil

The evaporator coil, located inside the indoor air handler, is responsible for absorbing heat from the indoor air (the cooling process). When the coil surface is coated with dirt, dust, or biological film, its ability to transfer heat is severely compromised.

• Reduced Heat Exchange Efficiency: The dirt layer acts as an insulator, increasing the thermal resistance between the indoor air and the refrigerant circulating inside the coil. This prevents the system from efficiently moving heat out of the air.

• Increased Run Time: Since the coil cannot cool the air quickly, the compressor, which is the most energy-intensive component of the AC system, must run for significantly longer periods to achieve the thermostat's setpoint. Longer run times translate directly to higher electricity consumption.

• Lower Capacity (Loss of BTUs): A dirty coil forces the system to operate at a lower cooling capacity (measured in BTUs). To compensate, the system consumes more energy to achieve the same cooling effect as a clean system.

• Risk of Freeze-Up: Severe coil fouling restricts airflow across the coil. Low airflow causes the refrigerant temperature inside the coil to drop excessively, potentially below 32∘F. When the coil freezes, it completely stops cooling and forces the compressor to run uselessly, wasting large amounts of electricity.

2. Effect of a Dirty Blower Wheel

The blower wheel, or fan squirrel cage, is responsible for moving air across the evaporator coil and pushing conditioned air through the ductwork to the living spaces. Fouling on the wheel impacts both airflow volume and motor efficiency.

• Aerodynamic Loss: Dust and grime accumulate on the curved blades of the squirrel cage, altering their designed shape. This aerodynamic fouling reduces the fan's efficiency in moving air (cubic feet per minute, or CFM).

• Increased Static Pressure: To deliver the required volume of air through the restrictive ductwork, the system must overcome static pressure. A dirty blower wheel struggles to overcome this pressure, forcing the motor to work harder.

• Energy Penalty on the Motor: The blower motor (often a Permanent Split Capacitor, or PSC motor) is constantly struggling against the aerodynamic and static pressure losses. When a motor is forced to work harder to maintain airflow, its amp draw increases, consuming more electricity than its rated load.

• The Vicious Cycle: Reduced airflow from a dirty wheel further exacerbates the problem of a dirty coil by reducing heat transfer efficiency, linking the two components and compounding the energy waste.

The Bottom Line for Energy Consumption

Regular cleaning restores the components to their original design efficiency:

• Clean Coil: Maximizes heat transfer, reducing the compressor run time required for cooling.

• Clean Blower: Maximizes airflow (CFM) while minimizing the motor's power consumption (watts), ensuring that the cold air generated by the coil is delivered efficiently.

Studies show that simply maintaining a clean evaporator coil can lead to 5% to 15% savings in cooling energy consumption. The combination of clean coils and a clean blower wheel ensures the entire system's Seasonal Energy Efficiency Ratio (SEER) is maintained near its rated value, directly minimizing the homeowner's energy costs.

Energy Savings via Duct Sealing

The most substantial and scientifically supported energy savings related to ductwork come from sealing leaks discovered during the cleaning process, which addresses air distribution losses.

1. Eliminating Conditioned Air Loss (Duct Leakage)

Duct leakage is the single largest energy waste associated with the air distribution system.

• Air Leakage Impact: Studies show that a typical residential home loses 20% to 40% of its conditioned air due to leaks and holes in the ductwork. If ducts run through unconditioned spaces (attics, crawlspaces, garages), this leakage is equivalent to dumping heated or cooled air directly outdoors.

• Energy Savings: When ducts are properly sealed using mastic or specialized aerosol sealant, the heating and cooling load on the HVAC unit is instantly reduced. The system now delivers nearly 100% of its conditioned air to the living space, allowing the furnace or AC to run for significantly shorter periods. This results in massive, verifiable energy savings and a direct reduction in utility bills.

2. Preventing Unconditioned Air Intrusion

• Contaminant Infiltration: Leaky return ducts running through attics or crawlspaces can suck in hot, humid attic air in the summer (or cold air in the winter).

• Increased System Load: This forces the AC system to cool and dehumidify air that should not have entered the system, greatly increasing the latent load and sensible load on the unit and driving up energy consumption. Sealing these return leaks eliminates this unnecessary load.

3. Improving System Balance

• Restoring Design Flow: Duct sealing helps restore the designed balance of the system, ensuring the correct Cubic Feet per Minute (CFM) reaches each register. This improves comfort and, critically, ensures the coil gets the proper airflow, preventing the coil from operating inefficiently.

In summary, while a clean duct surface offers minimal direct energy benefit, the duct sealing and remediation that typically occur during a duct inspection provide one of the most cost-effective methods for achieving long-term energy savings in a building.