Energy Efficiency and Interior Environment
Energy Efficiency and Interior Environment
This domain tests the energy envelope and the interior conditions that affect health and comfort: insulation, fenestration, air sealing, duct insulation, ventilation, and light.
Envelope and systems
- The prescriptive path sets minimum insulation R-values by climate zone for ceilings, wood-frame walls, floors, basement walls, slabs, and ducts. An alternative U-factor trade-off path may be used where the code permits.
- Fenestration must meet maximum U-factor and solar heat gain coefficient limits by climate zone. Skylights and doors have separate criteria.
- Air sealing is required at penetrations, seams, top plates, rim joists, and other leakage paths. Ducts in unconditioned space need insulation and sealed joints.
- Fireplaces must have gasketed doors or outdoor combustion air where required; recessed luminaires must be rated for insulation contact or protected.
- Interior environment rules require natural light and ventilation, or mechanical alternatives. Bathrooms generally need 50 cfm intermittent or 20 cfm continuous exhaust; kitchens need higher intermittent exhaust.
Worked example
A habitable room is 12 ft by 14 ft, or 168 sq ft. The glazing minimum is 8% x 168 = 13.44 sq ft. The openable ventilation minimum is 4% x 168 = 6.72 sq ft. A fixed 4 ft x 5 ft window provides 20 sq ft of glazing, so it meets the light requirement, but it provides zero openable area and fails ventilation unless mechanical ventilation is provided. A 3 ft x 3 ft operable window provides 9 sq ft of openable area and passes both tests.
Traps
Do not calculate light and ventilation from the whole dwelling when the code applies room by room. Do not assume a large fixed window satisfies ventilation. Do not ignore duct sealing because the insulation value looks adequate. Do not mix prescriptive R-values with U-factor limits without following one consistent compliance path.