How Is Single-Family Title 24 Compliance Designed and Proven?

The compliance model is only as good as its inputs, so the engineer builds it from the permitted design — not from placeholders. Every envelope assembly, every window with its U-factor and solar heat gain coefficient, the HVAC equipment efficiencies, the duct design, the water heating system, and the lighting are entered as designed. The software then computes the proposed design's energy budget and compares it to the standard design's budget; the margin between them is the compliance result the permit reviewer checks. Design iteration happens in the model. If the first run fails, the engineer tests real fixes — better glazing, moving ducts inside conditioned space, upgrading water heating, adjusting the solar size — and re-runs until the design passes with a comfortable margin. This modeling happens during design development, not at permit time, because the fixes it reveals (a different window package, a relocated air handler) are cheap on paper and expensive after permit. The compliance forms generated from the final model become part of the permit set the jurisdiction reviews.

The photovoltaic design is integrated with the compliance model. The engineer sizes the array per the code's requirements, lays it out on the roof plan with fire-code setbacks and access pathways, and designs the electrical interconnection — inverter location, conduit routing, panel capacity, and the utility interconnection the project needs. The array in the model matches the array on the plans, because the HERS rater and the inspector will both check. HERS verification is planned during design, not discovered at final inspection. The engineer identifies which modeled measures require field verification — duct leakage testing, refrigerant charge verification, airflow measurement, insulation quality inspection, ventilation rate verification — and designs the systems so they can be tested: accessible equipment, testable duct configurations, and ventilation systems with measurable airflow. The compliance forms, the plans, and the verification requirements are packaged together so the builder, the rater, and the inspector all work from the same documented design.

Confirm these items before the Title 24 package is submitted: • Compliance model built from the actual permitted design: envelope, systems, lighting, and solar • Proposed design beats the standard energy budget with margin, verified in the compliance software • Window, insulation, and equipment specifications in the model match the plans and schedules • Solar array sized per code, laid out with fire setbacks, and electrically designed for interconnection • Compliance forms generated from the final model and included in the permit set • HERS-verified measures identified; systems designed for accessible field testing • Duct location, sealing, and insulation designed to both the model and the verification protocol • Builder and HERS rater coordinated on the verification scope before construction starts