Zero Energy Ready Home™ Certified Manufactured Homes Program
Frequently Asked Questions
ENERGY STAR v3
DUCTS IN FLOOR CAVITIES
Q: What does “ducts in floor cavities shall be enclosed by floor insulation” mean in Exhibit 1.
A: If you have a duct in a floor cavity, you should either:
have full depth insulation to the exterior of the duct; OR
have insulation to the exterior AND the cavity is filled.
Example, if the floor insulation is R-22, you could have R-22 to the exterior of the duct or if you can't fit R-22 in the space between the duct and the exterior, you must have insulation to the exterior AND the floor cavity should be filled with insulation where there is room around the duct.
CROSSOVER DUCT
Q: Does this requirement “Crossover ducts, ducts in unconditioned attics, and other ducts in unconditioned space shall have at least R-8 duct insulation.” apply to in-floor crossover ducts?
A: If the in-floor crossovers are above the floor insulation and fully within the conditioned space, then it is considered in compliance with this requirement, and does not require additional insulation.
Q: If a home has overhead ducts and those ducts are either covered in R8 or fully covered with blown insulation would those be considered external ducts and therefore require the site inspection?
A: The program recognizes that it is impractical for Certifiers to inspect crossover duct connections in the attic after a home has been fully installed. Therefore, as long as ducts in the attic are insulated to at least R-8 per program requirements, they do not need to be included in the plant’s sample for 2% inspections in the field. However, Certifiers should inspect attic crossover connections during home production as part of the annual in-plant review to ensure compliance with program requirements, as follows:
Version 2 program requirements:
Ducts in attics shall be fully buried in attic insulation.
Crossover ducts and other ducts in unconditioned space shall be insulated to R-8.
Version 3 program requirements:
Crossover ducts, ducts in unconditioned attics, and other ducts in unconditioned space shall have at least R-8 duct insulation. Ducts are not required to be buried within ceiling insulation. If they are, EPA recommends but does not require that the ducts comply with the insulation and leakage requirements of Sections 403.3.3 and 403.3.7 of the 2021 International Energy Conservation Code, as well as the vapor retarder requirements of Section 604.11 of the 2021 International Mechanical Code or Section M1601.4.6 of the 2021 International Residential Code. Burying ducts within ceiling insulation is not an alternative to the requirement that ducts in unconditioned attics have at least R-8 duct insulation.
POINTS SYSTEM
Q: Can one get both points (heat pump and high-efficiency furnace) for hybrid-fuel system?
A: No. You cannot get points for both.
Q: When ENERGY STAR refrigerator points are used, are secondary bar refrigerators required to be ENERGY STAR certified?
A: Yes. All appliances subject to labeling need to be ENERGY STAR certified. For products in categories which are not covered by ENERGY STAR product criteria, such as combination all-in-one clothes washer-dryers, these products are exempt.
ENERGY STAR VERSION
Q: For the current construction to ENERGY STAR, is the existing standard Version 2 or 3.
A: Manufactured homes produced before December 31, 2025, are permitted to be certified using either Version 2 or Version 3 of the program requirements. Manufactured homes produced on or after January 1, 2026, must be certified using Version 3 of the program requirements. ENERGY STAR Version 3 is a pre-requisite for ZERH MH.
ZERO ENERGY READY HOMES
FACTORY INSTALLED MEASURES
1.1. ROOF TRUSS HEEL HEIGHT
Q: Is this requirement for “non-catheterized” ceilings only?
A: The requirement is for ceilings with attic spaces. The benefit of raised heel truss in a cathedral ceiling application would be severely limited.
2.3. SEALING FLOOR PENETRATIONS
Q: Do all other penetrations through the floor; i.e.: tub/shower p-traps need to be sealed if the bottom board is used as a barrier? Also, does this include sealing pipes, wires coming up through floor into a wall cavity?
A: Yes, all need to be sealed: “All plumbing, electrical, and HVAC penetrations through the floor must be sealed at the floor, even where the floor is not serving as the air barrier.”
2.4. SEALING BOTTOM BOARD OR BELLY BOARD
Q: Can the hole in the bottom board cut behind access panels be taped?
A: Yes, but you need to tape it back securely with long-lasting tape.
Q: If the bottom board is used as a barrier, does one still need to seal around the register boot at floor decking location?
A: Yes.
Q: Could foam tape be used behind the bottom board instead of taping it?
A: Foam tape can be a part of the solution but the detail will have to be reviewed by the certifier.
Q: Can the house wrap over the bottom board be overlapped or will the bottom board need to be taped to the rim rail around perimeter?
A: Overlapping the house wrap does not meet the requirement.
3.1. VENTILATION AIR FLOW RATE
Q: Can the equation in ASHRAE 62.2 be used to calculate design air flow instead of the table method.
A: Yes. Both the equation and table method provided in ASHRAE 62.2 are acceptable. Refer the Certifier’s Plant Inspection Worksheet.
Q: Does a P.O.S. system count for whole house ventilation?
A: A POS system is not prohibited if a compliant ventilation system is also installed.
3.2. VENTILATION CONTROL
Q: What type of automatic control is required on whole house ventilation? If an exhaust fan rated for continuous operation is used, can it be a toggle on/off switch?
A: If it is sized properly and rated for automatic operation then an on/off switch is sufficient.
4.3. MEASURED DUCT LEAKAGE
Q: Is the 10% duct leakage testing based on “number of homes” or “number of floors”?
A: Testing is based on the number of homes. Refer the Policy Record.
5.1. KITCHEN EXHAUST AIRFLOW RATE
Q: Is there any alternative to meet 5.1 Kitchen Exhaust Airflow Rate?
A: The following guideline can be used as an alternative to testing kitchen/microwave range hoods: Mandatory Technical Requirements – Local Mechanical Exhaust Airflow Requirements for Kitchens Guideline. Refer the Certifier’s Plant Inspection Worksheet.
Q: Will a “space maker” microwave need to meet the same requirements as a range hood for ventilation CFM's? Space maker is a marketing term for Over-the-Counter Microwave/Rangehood.
A: If it is being used as a range hood it needs to meet the air flow requirements.
5.2. BATH EXHAUST AIRFLOW RATE AND SOUND LEVEL
Q: Can the CFM rating on the bath fan and whole house fan be used or will it be tested in plant?
A: Testing is required for plant certification.
Q: Do all the bath fans in a home need to be tested?
A: Yes.
Q: Are there any tips to increase the delivered CFM?
A: A typical 4” plastic flex duct reduces the airflow substantially, so select exhaust fan capacity accordingly. Reducing kinks and bends in ducts and using a larger duct diameter or a 4” metal dryer duct helps maintain airflow.
7.1. DRAFTED OR DIRECT-VENTED APPLIANCES
Q: Are fireplaces allowed?
A: Yes. But as per the ENERGY STAR Requirement wood burning fireplaces must use air-tight, gasketed doors.
9.1. DHW DISTRIBUTION EFFICIENCY AND WATER FIXTURES
Q: Is there data on how long ½” or ¾” lines can be to stay under 1.2 gallons?
A: Yes, this information is available for various pipe material types from the following website - https://www.epa.gov/sites/default/files/2017-02/ws-homes-hot-water-volume-tool.xlsm
10.3. BITUMINOUS MEMBRANE
Q: For bituminous membrane installed over valleys and roof deck penetrations; is there a minimum size of membrane required at the roof decking penetrations?
A: None stated in the guidelines.
12.2. HARD-SURFACE FLOORING
Q: Does linoleum count as hard surface flooring?
A: Yes.
Q: Does hard-surface floor need to be installed within the facility or can it be installed in the field?
A: It can be installed on field if the instructions are included in the installation manual or DAPIA and there is no carpet installed in those locations when shipped.
13.1. RELATIVE HUMIDITY LEVEL
Q: Should the dehumidifier drain run to the edge of the house like the other similar drains?
A: Yes, it should drain to the edge of the house.
Q: What size drain should the dehumidifier have?
A: The same size as the water heater relief drain.
Q: Does the plug for the dehumidifier need to be on a dedicated circuit?
A: No.
Q: All ACs provide some dehumidification. Will a home with furnace with AC/heat pump meet the requirement?
A: A home with AC/heat pump alone does not comply. In swing seasons the cooling demand is low so there is insufficient dehumidification.
13.2. DUCTWORK IN CAVITIES
Q: Does this requirement affect return air grill application above doors and through doors?
A: This applies to vents through walls above doors, but as doors are a self-contained component, a sleeve is not required through them.
13.3. OZONE GENERATORS
Q: Is this for requirement for equipment specifically designed to generate ozone?
A: Yes.
15.1. DRY AND CLEAN HVAC SYSTEM
Q: Does the furnace need to be covered for transportation?
A: The furnace must be protected during production to prevent dirt and debris from getting inside. The furnace box can be used for this purpose.
Q: How should one verify that the HVAC duct is clean?
A: Vacuum debris out of floor ducts immediately after cutting them open and seal them as soon as possible.
16.2. CONDUIT TO INVERTER
Q: The initial intent of the conduit from designated inverter location to PV array location was to provide ease of installation for future PV installer to not need to penetrate the building assembly. If the inverter is on the exterior, does one need to provide this passageway?
A: No. Refer the Policy Record.
16.3. CONDUIT TO SERVICE PANEL
Q: Does solar array conduit have to be continuous from breaker panel to other locations?
A: No. If the proposed inverter location is on the exterior, then the conduit can go from the electric panel through the floor or the wall to the vicinity of the inverter location, capped at both ends.
FIELD INSTALLED MEASURES:
2.1. OUTDOOR PACKAGED HVAC UNITS
Q: Outdoor packaged units must have outside duct runs that are less than 20 feet in length each for supply and return; and, have exterior ducts wrapped with ≥ R-8 insulation. Does the 20 feet include crossover ducts?
A: Crossover ducts do NOT count towards packaged unit duct maximum length.
2.3. VENTILATION BEFORE OCCUPANCY
Q: Can the manufacturer put a statement in the homeowner’s manual which advises homeowners to operate whole house ventilation at highest rate for first few months in order to meet this section?
A: Yes.
3.10. SEALED BASEMENTS/CRAWLSPACES
Q: Are crawl spaces required to be sealed?
A: The requirement for sealed crawlspace is waived because 3.10 states that block crawl spaces must be sealed and conditioned. However, 24 CFR part 3285.505 interprets a block crawl space as “skirting,” and section 3285.504 defines skirting as comprised of “weather resistant materials”. Further, if applied as a skirting, the masonry materials would be required under section 3285.505 to be provided with ventilation openings. In cases where requirements of the federal codes or manufacturers’ installation instructions overlap or conflict with DOE ZERH program requirements the code shall control compliance. Thus, DOE ZERH program waives requirement 3.10 for sealing and conditioning the block crawl space. Refer the Model addendum to the Policy Record.
CERTIFICATION PROCESS:
ENERGY STAR LABEL FOR ZERH HOMES
Q: Are there ZERH labels that go into certified homes? And specifically for the certification homes, does one need to put energy star labels?
A: Yes, since ENERGY STAR is a prerequisite, plants must label ZERHs as ENERGY STAR. In addition to the ENERGY STAR labels, ZERHs will get a certificate when the home is set and completed on site. There is no ZERH label. The ENERGY STAR label must be applied first to get the certificate.
Q: What if the plant fails to meet a certain requirement during the plant inspection?
A: Plant certification will not be complete until all discrepancies are resolved, and the plant has demonstrated compliance with all mandatory in-plant requirements. For the items marked as approval pending/not approved, the plant can demonstrate compliance on another home to complete the plant certification process. Only homes meeting all requirements may be certified.
ADDITIONAL MEASURES
BAFFLES
Q: Should attic baffles be installed in both single wide and double wide or just double wide?
A: Both.
AIR BARRIER INSTALLATION CRITERIA
Q: Does the smoke alarm ring need to be sealed to the ceiling or just the box it is mounted on?
A: Seal at the box gasket.
Q: Do the electrical wire holes from the interior walls through to the exterior walls need to be sealed?
A: No.
WINDOWS, SKYLIGHTS, AND EXTERIOR DOORS
Q: Is the gap between the framing and windows or doors required to be sealed or filled?
A: ZERH requires an air seal at this location which can be achieved by sealing this gap or with continuous butyl tape on the window flange.