The reference design is calculated using the same inputs, assumptions and algorithms as the standard design except for the following requirements:
• Air handler power. The air handler power is 0.8 W/cfm.
• Air infiltration rate. The air infiltration rate is 7.2 ACH50.
• Cooling airflow. The air handler airflow is 300 CFM/ton.
• Duct R-value. The duct R-value is R-8.
• Duct leakage rate. The duct leakage rate is modeled as an HVAC distribution efficiency of 80 percent.
• Insulation Installation Quality (QII): QII is modeled as “improved”.
• Wall construction. Climate zones 2-15 have 2x4 R-13 walls. Climate zones 1 and 16 have 2x6 R-19 walls.
• Roof/ceiling construction. Climate zones 2-15 have R-30 ceiling. Climate zones 1 and 16 have R-38 ceiling. No climate zones include radiant barriers or cool roofs.
• Floor construction. Climate zones 2-15 have 2x10 R-19 floors. Climate zones 1 and 16 have 2x10 R-30 floors.
• Slab edge insulation. Climate zones 1 and 16 include R-10 insulation 24 inches deep.
• Window U-factors. Climate zones 2-15 have 0.65 U-factor. Climate zones 1 and 16 have 0.35 U-factor.
• Window SHGC. All windows have 0.4 SHGC.
• Window area. When the window area is below 18 percent of the floor area, the reference design has the same area as the proposed design. Above 18 percent, the reference design has 18 percent.
• HVAC equipment efficiencies. HVAC equipment meets NAECA requirements in effect in 2006 such as 78 percent AFUE for gas central furnace, 13 SEER for central AC.
• Water heating efficiency. Water heating modeled as a 40 gallon storage water with a 0.594 EF if gas or a 0.9172 EF if electric.
•Appliance and plug load energy use and internal gains. Energy use and internal gains for appliance and miscellaneous plug loads are modeled as specified the ANSI/RESNET/ICC 301-2014 Standard.