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Whole-House Mechanical Ventilation System meets ASHRAE 62.2

DOE Zero Energy Ready Home (Revision 07)

Exhibit 2 DOE Zero Energy Ready Home Target Home.
The U.S. Department of Energy’s Zero Energy Ready Home program allows builders to choose a prescriptive or performance path. The DOE Zero Energy Ready Home prescriptive path requires builders to meet or exceed the minimum HVAC efficiencies listed in Exhibit 2 of the National Program Requirements (Rev 07), as shown below. The DOE Zero Energy Ready Home performance path allows builders to select a custom combination of measures for each home that is equivalent in performance to the minimum HERS index of a modeled target home that meets the requirements of Exhibit 2 as well as the mandatory requirements of Zero Energy Ready Home Exhibit 1.

Table 1 shows the minimum exhaust fan efficacy requirements in cubic feet per minute per Watt for ASHRAE 62.2-compliant ventilation in the hot, mixed, and cold climates.

DOE ZERH Target Home HVAC Equipment Requirements
Table 1. DOE ZERH Target Home HVAC Equipment Requirements ​(Source: DOE Zero Energy Ready Home (Revision 07)).

The whole-house mechanical ventilation system can be designed to meet the ventilation requirements in one of several ways (DOE 2012): supply-only ventilation, exhaust-only ventilation, balanced ventilation with a heat recovery ventilator (HRV) or energy recovery ventilator (ERV), or intermittently balanced using a combination of timered exhaust fans and supply ventilation using fresh air intake ducts that are attached to the central air handler or equipped with their own fan.

For more information about whole-house ventilation options, see the guide Whole-Building Delivered Ventilation, which describes exhaust, supply, and balanced ventilation strategies.

How to Determine Fan Efficacy

The efficacy of the fans included in the whole-house ventilation system must be verified. Verifying the fan efficacy depends on the information available. The cfm/W may be listed on the specification sheet for the fan. If multiple values are listed, choose the airflow (cfm) shown on the mechanical plans and 0.1 in. of static pressure (in. w.c.). If efficacy is not listed, it can be calculated from published watts and specified airflow (cfm). For example, a fan with an airflow of 80 cfm at 0.100 in. w.c. and a wattage of 48 W has an efficacy of (80÷48=) 1.67 cfm/W.  If the wattage is not specified, it can be calculated from the fan voltage and amperage. (To calculate watts, multiply volts times amps times an assumed power factor for the fan motor (for example 0.75PF). Also see Continuous Supply/Exhaust Fan Ratings.

Climate zones are based on the Climate Zone Map found in the 2015 International Energy Conservation Code (2015 IECC Figure R301.1):

IECC climate zone map
Figure 1. IECC Climate Zone Map

 

More Info.

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Case Studies

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References and Resources*

  1. Author(s): International Code Council
    Organization(s): ICC
    Publication Date: May, 2014

    Code establishing a baseline for energy efficiency by setting performance standards for the building envelope (defined as the boundary that separates heated/cooled air from unconditioned, outside air), mechanical systems, lighting systems and service water heating systems in homes and commercial businesses.

  2. Author(s): ASHRAE
    Organization(s): ASHRAE
    Publication Date: January, 2013

    Standard defining the roles of and minimum requirements for mechanical and natural ventilation systems and the building envelope intended to provide acceptable indoor air quality in low-rise residential buildings.

  3. Author(s): Department of Energy
    Organization(s): DOE
    Publication Date: August, 2012

    IECC code note explaining new fan efficacy requirements, along with how to determine which fans are affected by the new fan requirements.

  4. Author(s): U.S. Department of Energy
    Organization(s): DOE
    Publication Date: May, 2019

    Standard requirements for DOE's Zero Energy Ready Home national program certification.

  5. Author(s): Maxwell, Berger, Zuluaga
    Organization(s): CARB, Steven Winter Associates, SWA
    Publication Date: July, 2014

    Report outlining research that helps inform best practices for air sealing multi-family buildings in the Northeast.

Last Updated: Tuesday, July 30, 2019

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