This refers to the amount of leakage from the air distribution ducts as measured with a "Duct Blaster" or similar diagnostic device. During plant certification, the manufacturer in consultation with the certifier will determine the target leakage rate and steps required to achieve that rate (e.g., duct sealing strategies). The midrange leakage rate of 5% should be readily achievable with currently available duct design and sealing techniques. The duct leakage values in the ENERGY STAR design packages are measurements of air leakage to the outside when the ducts are depressurized to negative 25 pascals. The values are based on air handler airflow rates and correlate approximately to cubic feet per minute of leakage divided by the floor area of the home. When measured in the plant, only total duct leakage can be determined. About 50% of total measured duct leakage will leak to the outside after the home is set.
This refers to the rated seasonal efficiency of the equipment used for space heating.
- Heat pump efficiencies are listed by the Air-Conditioning and Refrigeration Institute (ARI) in the ARI Directory of Certified Unitary Products. Heat pumps in the heating mode are rated in terms of Heating Seasonal Performance Factor (HSPF).
- Gas (natural and liquid petroleum) and oil burning furnace efficiencies are listed by the Gas Appliance Manufacturers Association (GAMA) in the Consumers’ Directory of Certified Efficiency Ratings for Heating and Water Heating Equipment. Fossil fuel-burning furnaces are rated in terms of Annual Fuel Utilization Efficiency (AFUE).
This refers to the ability of the home’s envelope to resist heat flow and is calculated in the same manner as the Uo-value referred to in the HUD standards.
This refers to the ability of the window to block solar heat from entering the home. The higher the SHGC, the more solar heat is transmitted through the window. To meet the requirement, calculate the area-weighted average of the SHGCs for all the windows (multiply each window area by its whole window SHGC, add the results together, and divide by the total window area). ENERGY STAR certified homes do not require the use of ENERGY STAR qualified windows, nor does the use of ENERGY STAR qualified windows make a home qualify as ENERGY STAR.
This refers to the efficiency rating of the hot water heater (WH). Hot water heaters are rated in terms of Energy Factor (EF). Different EF levels are provided for gas and for electric equipment. In some packages a high efficiency water heater is required. This is indicated by a check mark in the “High Efficiency WH” column in the design packages. The high efficiency WH requirement may be met in either of two ways:
- An EF of at least 0.59 for gas or at least 0.91 for electric water heaters.
- A water heater with a minimum EF of 0.56 for gas heaters and 0.88 for electric heaters heater wrapped with a minimum of R-5 insulation. Check with the water heater manufacturer about restrictions on wrapping a specific water heater.
Programmable thermostats that can be automatically set back to lower temperatures in the heating season or set up to higher temperatures in the cooling season can generate significant energy savings. Refer to the column labeled Programmable Thermostat to see whether a programmable thermostat is needed for the home.
This refers to the equipment rating as certified by ARI and published in the ARI Directory of Certified Unitary Products. Air conditioners and heat pumps in the cooling mode are rated in terms of Seasonal Energy Efficiency Ratio State Primary(SEER). All ENERGY STAR certified homes must be equipped with cooling equipment rated not less than National Appliance Energy Conservation Act (NAECA) minimum requirements (13 SEER, 7.7 HSPF). While not an ENERGY STAR requirement, cooling equipment should be correctly sized (PDF, 3.9MB).
For the electric resistance heating packages for Climate Region 1, a heat recovery ventilator (HRV) must be used to maintain the fresh air ventilation requirements of the HUD Code. A heat recovery ventilator (also called an air-to-air heat exchanger) is a ventilation system that consists of two separate air-handling systems-one collects and exhausts stale indoor air and the other draws in fresh outdoor air and distributes it throughout the home. At the core of an HRV is a heat transfer module. Both the exhaust and fresh air streams pass through this module and the heat from the exhaust air is used to preheat the fresh air stream. Only the heat is transferred; the two air streams remain physically separate. Typically, an HRV is able to recover 70-80% of the heat from the exhaust air and transfer it to the incoming air. This dramatically reduces the energy needed to heat fresh incoming air.
All ENERGY STAR certified homes must also contain the following features:
Minimum Duct Insulation
This refers to the rated insulation value (R-value) of materials used for insulating all ductwork, including the exterior crossover duct. Attic and floor insulation covering ductwork may count towards this requirement.
- Climate Regions 1 and 2: a minimum of R-8 is required
- Climate Regions 3 and 4: a minimum of R-6 is required
All ENERGY STAR certified homes must have whole-house leakage rates, calculated based on blower door measurements, that do not exceed 7.0 ACH50.("Electric resistance packages in Region 1 require a maximum shell leakage rate of 4.0 ACH50.) Whole-house leakage rates are determined by the ENERGY STAR Certifier during plant certification and as part of random-sample field evaluations.
All ENERGY STAR certified homes placed over basements must also meet the following requirements:
- Unconditioned basement:
Unconditioned basements are separated from the living area and not intentionally heated. The walls of the interior stairwell are insulated to the same levels as the exterior walls of the home. Doors to the basement are insulated and weather-stripped.
- Semi-conditioned and conditioned basements:
For heated basements and basements separated from the main living space by uninsulated stairwells are required to have exterior basement wall insulation with the following nominal (insulation material) R-values:
- Climate Region 1: R-13
- Climate Region 2: R-10
- Climate Region 3: R-10
- Climate Region 4: R-0