When it comes to passing ENERGY STAR v2.5 or v3.0, there are a few items that must happen
The HERS Rating of the design home must be equal to or lower than that of the ENERGY STAR v2.5/v3.0 Reference HERS Index Target. In addition to the HERS Rating - there are a few other mandatory checks that REM/Rate will perform.
1. The duct leakage to outside must be lower than 4 CFM25/CFA for ESv3.0 or 6 CFM25/CFA for ESv2.5. Smaller homes (<= 1200 sq ft) have <= 5 CFM25/CFA. If total leakage is lower than 4 CFM25/CFA, then leakage to outside need not be tested. A small home must have total duct leakage <= 5 CFM25/CFA. Look at the Air Leakage Report to determine if the duct leakage levels meet these requirements.
2. Envelope insulation levels must meet the requirements of Table 402.1.1 in the 2009 IECC. There are two methods to do this. One is to check the checkbox in the Mandatory Requirements screen that states that ALL envelope insulation levels meet the levels in Table 402.1.1. Otherwise REM will conduct a UA calculation of the design home and 2009 IECC reference home to determine if the home meets these levels. This analysis does not include the windows or doors. So a home may pass the 2009 IECC UA Compliance, but not pass this section. If you go to the 2009 IECC UA Report and subtract the windows from the total in both homes, you can see if this is the reason it does not pass for ENERGY STAR.
3. Slab on grade insulation must be >= R-5 for the depths listed in Table 402.1.1 in the 2009 IECC.
4. All envelope insulation must be Grade I or Grade II with insulated sheathing (R-3 or better for climate zones 1-4, or R-5 or better for climate zones 5-8). A building file that utilizes libraries with Path/Layer construction may have insulation grades other than I. When creating a new library - first use the Quick Fill and set the Insulation Grade to I and then move to Path/Layer. If you have an existing library in Path/Layer - go back to Quick Fill, set the Insulation Grade to I and then rebuild the library same as before. The Insulation Grade is not reported on the Path/Layer side.
5. Windows must meet the requirements of Table 402.1.1 in the 2009 IECC. REM will check each window for compliance or conduct a weighted average to see if the windows pass. Passing either method will show compliance with this topic.
6. Ducts in unconditioned spaces must meet the EPA requirements of R-6.
7. The rater must verify in the Mandatory Requirements screen that all checklists have been completed. The Thermal Enclosure, both HVAC checklists and either the Water Management or Air Quality checklists.
6. The mechanical ventilation rate in CFM must be within 100-120% of the ASHRAE 62.2010 flow rate. This is not a requirement for ENERGY STAR compliance but in for informational purposes.