Water Efficiency and Energy Performance in Homes
Water and energy carry 50 of the 110 points - 12 and 38 - and both are performance-based. The exam asks you to compute a saving or read a rating, not to name a fixture.
Water
Indoor baselines come from EPAct 1992 rates: 1.6 gpf toilets, 2.5 gpm showerheads at 80 psi, 2.2 gpm faucets and aerators. WaterSense fixtures beat those rates. Points scale with the percentage reduction in total water use, indoor plus outdoor. Outdoor savings come from native and climate-adapted planting, no potable irrigation, drip lines, ET-based controllers, and harvested rainwater or condensate.
Energy
The HERS Index is the currency. A reference home of the same size and shape scores 100; a net-zero home scores 0; each index point is roughly 1% of annual energy use, so lower is better. The EA prerequisite requires meeting ENERGY STAR for Homes requirements: envelope airtightness near 3 ACH50, duct leakage near 4 CFM25 per 100 sq ft of conditioned area, efficient equipment. EA credits then award points for each index point below a size-adjusted HERS target, up to the category cap, with further credits for efficient hot water distribution, HVAC commissioning, and active solar-ready design.
Worked example
A three-bedroom home has a LEED HERS target of 55. The rater models 40 and measures 2.8 ACH50 and 3 CFM25 per 100 sq ft. The 15-point improvement converts into energy points on the sliding scale, and the tight envelope satisfies the ENERGY STAR basis of the prerequisite. Had the blower door read 5 ACH50, the prerequisite would fail and the point total would not matter.
Traps that cost marks
- Reversing HERS direction - 30 is far better than 90.
- Assuming photovoltaics are mandatory; solar-ready is a credit.
- Computing water savings against a design baseline instead of the EPAct baseline.
- Forgetting that airtightness and duct leakage are field-measured, not drawn.