AirCycler Annual Ventilation Cost Calculator

Statement from Residential Energy Dynamics

This calculator was created for AirCycler^® by Residential Energy Dynamics, LLC (RED). This annual ventilation cost estimator continues our long-standing commitment to providing users with the best, unbiased information and calculation methods possible.

Introduction

The purpose of this calculator is to provide homeowners and contractors with estimates of the annual cost of operating a whole-building ventilation system using one of four AirCycler^® controls/systems or one of four generic HRV/ERV systems. The yearly cost includes the costs for heating and cooling ventilation air (fossil fuel and electricity) and the electrical cost for any fan or central furnace blower to move the ventilation air.

The actual cost for a particular home depends on several factors, most importantly, the required ventilation rate. To calculate this required ventilation rate for a particular home requires a measurement of the house air leakage, obtained from performing a blower-door test, equipment not available to most homeowners or contractors. For this reason, we decided to provide a range for the estimated ventilation cost based only on facts that homeowners are likely to know. These include ZIP code, living area, number of stories above ground level, number of bedrooms, and the price of heating fuel and electricity.

For increased accuracy, homeowners or their contractors may provide optional detailed inputs for exhaust fan airflow rate, exhaust fan wattage, air-handler blower wattage, and furnace airflow rate through the motorized fresh-air damper connecting the furnace ductwork to the outdoors.

General Assumptions

These assumptions are made for the low-end and high-end estimates of the reported cost range:

• The home is located within the United States.
• The home is a single-family, detached building.
• The ventilation rate is determined using ASHRAE standard 62.2-2013.
• The heating and cooling systems are properly sized so that the system will run continuously under outdoor design conditions.
• Indoor air temperature settings are 75℉ for cooling and 68℉ for heating. The heating and cooling systems operate when needed, based on these thermostat settings and outdoor weather data for the entered ZIP code.
• For the purposes of calculating the latent cooling load, the indoor air is assumed to be 55% RH at 75°F.
• Heating and cooling systems utilize a common central air handler furnace blower.
• For the purpose of calculating the electrical use of the central furnace blower while conditioning the ventilation air, the furnace blower is assigned an efficiency (electrical consumption to total energy consumption of the furnace or air conditioning unit) of 2.5%, a value falling between ECM and non-ECM motors, based on a Wisconsin field study of central furnace blowers. The same percentage is also applied to air conditioning units.
• Cooling system efficiency is 14.5 SEER (minimum efficiency for EnergyStar rating).
• Heat pump efficiency is 8.2 HSPF (minimum efficiency for EnergyStar rating).
• The Generic EnergyStar fan efficacy is 1.4 CFM/Watt (minimum IRC 2012 and 2015 requirement). This efficacy value may be overridden by selecting Custom fan specifications from the Exhaust Fan drop-down, and then entering values for Exhaust Fan CFM and Exhaust Fan Watts.
• Unless “Custom specifications” is selected for the Blower/Damper drop-down, these default assumptions will be used for the calculation:
  • For all AirCycler^® controls/systems using the central furnace blower, Average HRV with Furnace, and Average ERV with Furnace, the blower wattage is equal to (250 + (Living space)/10).
  • For all the AirCycler^® controls/systems using a central furnace blower, Average HRV with Furnace, and Average ERV with Furnace, the damper CFM airflow through the duct from the outdoors to the furnace return is 45 CFM (cubic feet per minute) greater than the required ventilation rate.
• For all AirCycler^® controls, except g2 + FanConnect Balanced, the ventilation system is unbalanced. Unbalanced ventilation systems interfere with the natural air leakage of the building, thereby slightly reducing the heating and cooling costs. To estimate this “energy credit”, the AIM-2 infiltration model, together with TMY3 wind and temperature data, are used to calculate hourly energy loss with and without ventilation. On the other hand, balanced ventilation systems — AirCycler^® g2 + FanConnect Balanced, Average HRV with Furnace, Average ERV with Furnace, Average Stand-alone HRV, and Average Stand-alone ERV — do NOT reduce air leakage, thus result in slightly higher commensurate operating costs.

Assumptions for Low-end Estimate

The low-end estimate is based on a home with the following characteristics:

• Older, possibly retrofitted, home that is just tight enough to require the minimum ventilation rate of 15 CFM.
• Heating system efficiencies are for mid-efficiency equipment:
  • Natural gas, propane: 83 percent AFUE.
  • Oil: 82 percent AFUE.
• The calculation that combines mechanical ventilation and infiltration uses the AIM-2 infiltration model and the 0.5 unbalanced fan rule.

Assumptions for High-end Estimate

The high-end estimate is based on a home with the following characteristics:

• Newly constructed according to the International Energy Conservation Code 2012 or 2015, which have the same air tightness requirements.
• Heating system efficiencies comply with the minimum requirements for new EnergyStar appliances:
  • Natural gas and propane: 95 percent AFUE.
  • Oil: 85 percent AFUE.
• The calculation that combines unbalanced mechanical ventilation and infiltration uses the AIM-2 infiltration model and the quadrature fan rule.

Calculator Inputs

The following items must be either selected from drop-down menus or entered in an input box. The appearance of some items in the Estimator depend on other selected items.

• Ventilation System - Select the AirCycler^® control/ventilation configuration or one of four HRV/ERV configurations being used in the home. The selection affects the calculation and also dictates whether some other inputs become visible/active.
  • SmartExhaust^™ - This control automatically turns on a bathroom exhaust fan each hour to satisfy the whole-house ventilation requirement, but only if the occupant use of the fan is otherwise insufficient. This is the default control selection.
  • g1 (FRV) Supply-only^™ - This controls a motorized fresh-air damper that allows fresh air to be drawn into the house using the central furnace blower at the same time that this fan is running for heating or cooling. If the central furnace blower does not run long enough in a given hour to satisfy the ventilation requirement, then the g1 turns on the furnace blower (with the damper open) to satisfy the ventilation requirement.
  • g2 + FanConnect^™ - This control configuration combines the g2 and FanConnect^™ controls. The g2 controls a motorized fresh-air damper that allows fresh air to be drawn into the house using the central furnace blower at the same time that this fan is running for heating or cooling. If the central furnace blower does not run long enough in a given hour to satisfy the ventilation requirement, then the FanConnect^™ control turns on a bathroom exhaust fan to satisfy the ventilation requirement.
  • g2 + FanConnect Balanced^™ - This control configuration combines the g2 and FanConnect™ controls. The g2 functions in the same way as in the g1 (FRV) supply-only mode. For the balanced mode, the FanConnect^™ turns on a bathroom exhaust fan whenever the motorized fresh-air damper is open. This configuration is primarily used to avoid pressurizing the home in cold climates.
  • Average HRV with Furnace - Heat Recovery Ventilator of average efficiency, connected to the air handler (furnace) ductwork and controlled in a manner requiring the air handler blower to operate whenever the HRV is operating. The HRV airflow is assumed to be balanced during operation. The average efficiency is determined by averaging HRV efficiencies listed in the Home Ventilating Institute (HVI) database of certified HRV equipment. The average efficiencies used are 1.16 CFM/Watt (efficacy); and Sensible Recovery Efficiency (SRE) of 0.70.
  • Average ERV with Furnace - Heat Recovery Ventilator of average efficiency, connected to the air handler (furnace) ductwork and controlled in a manner requiring the air handler blower to operate whenever the ERV is operating. The ERV airflow is assumed to be balanced during operation. The average efficiency is determined by averaging ERV efficiencies listed in the Home Ventilating Institute (HVI) database of certified HRV equipment. The average efficiencies used are 1.3 CFM/Watt (efficacy); Sensible Recovery Efficiency (SRE) of 0.68; and Latent Recovery/Moisture Transfer (LR/MT) of 0.45.
  • Average Stand-alone HRV - Heat Recovery Ventilator of average efficiency, providing balanced ventilation. The average efficiency is determined by averaging HRV efficiencies listed in the Home Ventilating Institute (HVI) database of certified HRV equipment. The average efficiencies used are 1.16 CFM/Watt (efficacy); and Sensible Recovery Efficiency (SRE) of 0.70. The HRV unit is operating in a stand-alone fashion with no direct interaction with a furnace air handler blower or ductwork.
  • Average Stand-alone ERV - Energy Recovery Ventilator of average efficiency, providing balanced ventilation. The average efficiency is determined by averaging ERV efficiencies listed in the Home Ventilating Institute (HVI) database of certified ERV equipment. The average efficiencies used are 1.3 CFM/Watt (efficacy); Sensible Recovery Efficiency (SRE) of 0.68; and Latent Recovery/Moisture Transfer (LR/MT) of 0.45. The ERV unit is operating in a stand-alone fashion with no direct interaction with a furnace air handler blower or ductwork.
• Exhaust Fan - This drop-down menu appears when the Ventilation System choices of SmartExhaust^™, g2 + FanConnect^™, or g2 + FanConnect Balanced^™ are selected.
  • Generic EnergyStar fan - EnergyStar-rated exhaust fan, having an efficacy of 1.4 CFM/watt.
  • Custom fan specifications -. When this is selected from the drop-down, the two inputs below must be entered for the determination of fan efficacy (CFM/Watt):
    • Exhaust Fan CFM - Airflow rate through the exhaust fan in CFM. It is best to measure the airflow, if possible. If measurement is not possible, use the rated airflow of the fan. This value is used to calculate the exhaust fan efficacy.
      • Default - blank
    • Exhaust Fan Watts - The rated wattage for the exhaust fan. This value is used to calculate the exhaust fan efficacy, CFM/Watt.
      • Allowed range - 0 to 400 Watts
      • Default - blank
• Blower/Damper - This drop-down menu appears when Ventilation System choice of g1 (FRV) Supply-only^™, g2 + FanConnect^™, g2 + FanConnect Balanced^™, Average HRV with Furnace, or Average ERV with Furnace is selected.
  • Use default values - The furnace blower default values and the default values for the CFM of the damper in the duct from the outdoors are used. Please see General Assumptions, above.
  • Custom specifications -. When this is selected from the drop-down and g1 (FRV) Supply-only^™, g2 + FanConnect^™, or g2 + FanConnect Balanced^™ is selected from the Ventilation System drop-down, both Blower Watts and Damper CFM must be entered. On the other hand, when Average HRV with Furnace or Average ERV with Furnace is selected from the Ventilation System drop-down, only Blower Watts must be entered (Damper CFM does not appear).
    • Blower Watts - The rated wattage for the furnace blower.
      • Allowed range - 0 to 4,000 Watts
      • Default - blank
    • Damper CFM - Enter the actual flow rate through the fresh air motorized damper controlled by the AirCycler control. This damper is located in a duct running from the outdoors to the furnace return ductwork. It is best to measure this airflow rate, if possible.
      • Maximum allowed value - 300 CFM
      • Default - blank
• ZIP Code - Enter a valid 5-digit US zip code. The closest TMY3 weather station data is used for the calculations. The “Heating Fuel Price" and “Electricity Price” inputs are filled with the appropriate 12-month statewide averages whenever a ZIP code is entered.
  • Default - Blank
• Floor Area - Enter the floor space, in square feet, of the livable part of the home. Include a basement only if it is finished for regular occupancy.
  • Allowed range - 500 to 6,000 square feet.
  • Default - Blank
• Bedrooms - Select the number of bedrooms in the home.
  • Options - 1 through 10.
  • Default - 3
• Stories - Select the number of above-ground stories for the home. Use 1.5 for a raised ranch or Cape Cod style home. Count a walk-out basement as one-half a story.
  • Options - 1, 1.5, 2, 2.5, and 3.
  • Default - 1
• Heating Fuel - Select the type of fuel used to heat the home.
  • Options - Natural gas, Propane, Oil (#2 is used for the calculations), Electricity (resistance heating), and Electricity with heat pump.
  • Default - Natural gas
• Heating Fuel Price - Initially this input box is blank, but it is automatically set (reset) to the average statewide fuel price over the last 12-month period whenever a valid ZIP code is entered. The average statewide prices for the listed fuels are obtained from the U.S. Energy Information Administration (EIA). These prices are undated monthly. Note: If the Heating fuel type selected is "Electricity" or "Electricity with heat pump", this input does not appear.
  • Default - blank
• Electricity Price - Initially this input box is blank, but it is automatically set (reset) to the average statewide electricity price over the last 12-month period whenever a valid ZIP code is entered. The average statewide price is obtained from the U.S. Energy Information Administration (EIA). These prices are updated monthly. Enter your cost in cents rather than dollars, for example, for five and one-half cents, enter 5.5 rather than 0.055.
  • Default - blank

Results

The Annual Ventilation Cost Range includes a low end and high end. Under these Low- and High-end Estimates, are some explanatory details:

• Low-end Estimate, $??? – The low end of the cost range is based on these assumptions:
  • Older home – The average tightness level and insulation values for older homes.
  • Leaky – The house leakiness is based on the minimum ventilation rate of 15 cubic feet per minute. The corresponding ACH₅₀ value is reported.
  • 15 ft³/min ventilation required – The required minimum whole-building ventilation rate for older, existing homes. For the low-end estimate, this value is always 15 cubic feet per minute.
• High-end Estimate, $??? - The high end of the cost range is based on these assumptions:
  • Newer home - Insulating values for newer homes are used.
  • Air tight - For the warmer U.S. climates (zones 1 and 2), the tightness level of 5 ACH₅₀ is used and for the colder U.S. climates (zones 3 to 7), the tightness level of 3 ACH₅₀ is used. These are the tightness levels required by the International Energy Conservation Code (IECC 2012 and 2015). The reported result will be either 3 ACH₅₀ or 5 ACH₅₀ and is dependent on the entered ZIP code.
  • ?? CFM ventilation required - For the high-end estimate, this value is calculated based on the other entries, such as living space, number of bedrooms, etc.

It is valid to interpolate between the high-end and low-end ventilation rates to find an estimated annual ventilation cost. For example, assume the high-end is $154 for 74 CFM and low-end is $41 for 15 CFM, using an AirCycler^® system and controls. If you find when using a more detailed ventilation sizing calculator, such as the Residential Energy Dynamics ASHRAE 62.2 tool, that the required ventilation is 60 CFM using the same location, living space, bedrooms, and stories; simply interpolate to find the estimated cost of $125.

If you have questions, contact AirCycler^® support. E-mail or call 781-834-1600.