Why a Los Feliz duct redesign and air balancing starts at the air path, not the brand
hillside heat, older ducts, pet dander, smoke days, and quiet bedroom expectations is the underlying pressure on most Los Feliz HVAC calls before a single brand is named. The homeowner is not buying a SEER2 number; they are buying a sleep environment, a smoke-day operating plan, or a return path that does not depressurize the laundry room into the conditioned space. Pre-1980 homes in Highland Park, Eagle Rock, Echo Park, Silver Lake, and parts of Pasadena often have undersized 14×25 returns and crushed flex serving back additions. Postwar Westside (Mar Vista, Culver City, Inglewood) frequently has 1-inch filter slots in hallway returns. Hot Valley homes (Sherman Oaks, Encino, Woodland Hills) live or die on duct integrity because attic temperatures push 130–140°F by 4 p.m. The audit separates those concerns into measurable line items.
Manual D total external static budget allocates 0.50 in. w.c. for PSC blowers, 0.80 for ECM. Friction rate FR = (TESP × 100) / Total Effective Length runs typically 0.06–0.10 in. w.c. per 100 ft. Return-air free-area rule is 144 sq in (1 sq ft) net per ton. Insulation requirement Title 24 §150.0(m)1: R-8 minimum on supply and return in unconditioned spaces (CZ 1–16, CZ 6 may use R-6).
Average summer high near 85°F with winter low around 47°F at an elevation of 430 ft and roughly 12 miles inland. CEC Climate Zone 9. The cooling design temperature for Manual J calculations runs about 92°F, with typical Manual J load landing in the 380-500 sq ft per ton band. Los Feliz was outside the January 2025 fire perimeters and downwind exposure was lighter than foothill or coastal areas, though regional smoke days still affected indoor PM2.5 in homes with leaky filter cabinets. The proposal that follows is a written engineering scope, not a brochure with a discount code.