Place HVAC supply registers at the perimeter (under windows / against exterior walls) — returns central
ROT/EXT-SUPPLY-REGISTER-PERIMETERDescription
Heating-dominant climates (most of US): supply registers at the perimeter, especially under windows + against exterior walls — counteracts the cold-surface effect. Returns in central halls or interior rooms. Cooling-dominant climates: high supplies in the ceiling are acceptable (cool air falls). For all-electric heat pump systems in cold climates, ceiling supplies are problematic — keep supplies low + perimeter.
Why this exists
Supply location dramatically affects comfort. Perimeter supplies under windows defeat the cold-window-radiation problem; central returns prevent stagnant air pockets. Architects should review the duct layout against this rule with the HVAC designer.
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
- Living spaces south-facing in cold climates · LIVING-SOUTH-FACING
- Mechanical room central, not corner · MECHANICAL-CENTRAL
- Water heater near fixtures · WATER-HEATER-NEAR-FIXTURES
- Roof orientation for future solar · SOLAR-ROOF-ORIENTATION
- Window-to-floor area: 12-20% for daylight quality; 8% is code minimum · ROT/EXT-WINDOW-AREA-TO-FLOOR
Last reviewed 2026-05-15.