Somewhere on sheet A-601 of most residential sets sits a table that decides a surprising amount of your compliance outcome: the window schedule. Fenestration is usually the single leakiest part of a California envelope, thermally speaking, and the schedule is where its numbers live. Reading it well is a skill. So is distrusting it appropriately.

The columns that matter to the energy model

  • Mark (W-101, W-102…): the ID that ties the schedule to the elevations and floor plans. Every downstream cross-check hangs off this.
  • Size: width by height, from which the model gets its glazing area. Watch for schedules listing rough opening versus unit dimension — a few inches per window compounds across a house.
  • U-factor: whole-assembly heat loss. The 2025 prescriptive limits split at 0.27 for smaller units and 0.30 for larger ones; NFRC-rated values only, not center-of-glass numbers from a brochure, which always look flatteringly low.
  • SHGC: solar heat gain coefficient. In cooling climates this number does more work than U-factor — and under the 2025 code's separate cooling metric it matters more than it used to.
  • Operation (fixed, slider, casement) and frame material: both feed the model, and operability also touches egress and ventilation requirements.

The schedule lies more often than you'd think

Not maliciously. Drawing sets evolve, and the schedule is a summary that someone has to keep synchronized by hand. In practice, plan sets drift in predictable ways: a window deleted from the south elevation during design development but never struck from the schedule. A “typ.” annotation covering three windows that were later resized individually. Quantities that say 2 where the elevations show 3. A remark column quietly noting “tempered” or “obscure” but not the changed glazing package that came with it.

Any one of these puts your energy model at odds with the building that will actually be inspected. The failure mode is slow: the model passes, the permit issues, and months later a rater or inspector counts windows on a wall and the arithmetic does not close.

Cross-checking: the tedious part that matters

The discipline is simple to state. For every mark on the schedule, find it on an elevation or plan; for every window drawn on an elevation, find its mark on the schedule. Then check that each window's wall assignment and orientation match reality, because the model cares which azimuth every square foot of glass faces. On a forty-window custom home this is an hour of honest, boring work, and it is exactly the work that tends to get skipped at 5 p.m. on a deadline.

This is why CertifiedT24's reader does the cross-check automatically: it reads the schedule and the elevations and the floor plans, reconciles the three, and shows you each window as a card with the source sheet it came from. When the schedule and the elevation disagree, the discrepancy is surfaced for a human decision instead of silently picking a side. The judgment stays yours. The counting does not have to.

None of this is glamorous. But of the corrections that come back from plan check on residential energy docs, fenestration mismatches are a steady, avoidable chunk. Ten careful minutes on A-601 — or an automated reconciliation you can review — is cheap insurance.