Tune window SHGC by orientation: high SHGC on south (passive solar); low SHGC on west / north
BASC Guide — guides/window-shgc-by-orientationDescription
Solar Heat Gain Coefficient (SHGC) measures how much solar energy passes through a window — high SHGC (0.40-0.60) admits more heat (useful in winter); low SHGC (≤ 0.25) blocks it (useful in summer). Best practice: south-facing windows in cold climates use SLIGHTLY HIGHER SHGC for passive winter heating, with adequate overhang to block summer sun. West + south-west windows in hot/cooling-dominated climates use LOW SHGC to block afternoon heat. North windows: SHGC mostly doesn't matter (no direct sun).
Why this exists
Tuning SHGC by orientation is a free architectural performance lever — same window cost, dramatic comfort difference. Architects should call out specific SHGCs on the window schedule by orientation; the default of one SHGC for the whole house misses the easy win.
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
Last reviewed 2026-05-15.