Where the water heater is electric, ZERH requires a heat-pump water heater (HPWH) with ≥ 2.0 UEF

Description

For ZERH-certified all-electric homes, the water heater must be a heat-pump water heater (HPWH) with Uniform Energy Factor (UEF) ≥ 2.0. The HPWH must be located where the surrounding air provides adequate heat-source (typically in a basement, garage, or conditioned utility room ≥ 700 cubic feet, OR in a smaller space with ducted intake/exhaust). Tank-style instantaneous gas water heaters with UEF ≥ 0.82 or instantaneous condensing gas water heaters with UEF ≥ 0.92 are acceptable alternatives in non-electric homes.

Why this exists

HPWHs use 2-3× less electricity than conventional resistance water heaters. The architect needs to size the utility room or pick a HPWH model with adequate working space — modern integrated HPWHs need ~700 cf surrounding air to source heat from. For ENERGY STAR-only certification a standard tank works; ZERH raises the bar.

Categories

Source

Solver enforcement

Browsable only — the solver does not currently enforce this directive (no spec-level data to check against). This entry exists so the architect personas can cite it in conversation and the user can read what the rule says.

Related directives

• Slab-on-grade vapor barrier + capillary break required · HUD RSDG §4.6
• Roof overhangs protect walls — 12-24 inches in humid climates; one foot per story below · HUD RSDG §5.6.5
• ENERGY STAR certification: HERS-index target + Rater field checklist + HVAC quality install · ENERGY STAR SFNH §Overview — Certification path
• Grade I insulation installation: no gaps, no compression, fully filling cavity, supported aligned with air barrier · ENERGY STAR SFNH §Rater Field Checklist — Section 1 (Insulation + Air Barrier)
• Continuous air barrier on all six sides of conditioned space — including rim joists, knee walls, attic floor · ENERGY STAR SFNH §Air Barrier — continuous on all six sides of every conditioned space