Static Pressure Budget Calculator

Build up total external static pressure (ESP) for fan selection. Sum duct, coil, filter, and terminal component losses with live budget tracking.

💨 Supply Side Components (in. w.c.)

Duct System
Supply duct system0.10–0.50 typicalin. w.c.
Supply diffusers / registers0.02–0.10in. w.c.
Coils & Filtration
Cooling coil (wet)0.40–1.20in. w.c.
Heating coil0.10–0.40in. w.c.
Pre-filter (MERV 8, clean)0.10–0.25in. w.c.
Final filter (MERV 13-14)0.25–0.60in. w.c.
OA & Dampers
OA intake louver + screen0.05–0.15in. w.c.
OA damper (open)0.05–0.15in. w.c.
Mixing box0.05–0.15in. w.c.
Return Side
Return duct system0.05–0.25in. w.c.
Return grilles0.02–0.08in. w.c.
Special / Misc
Energy recovery wheel / ERV0.40–1.00in. w.c.
HEPA filter0.80–2.00in. w.c.
Misc / other—in. w.c.

📊 Static Pressure Budget

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Total ESP (in. w.c.)
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Duct System (in. w.c.)
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Coils + Filters (in. w.c.)
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OA + Dampers (in. w.c.)
Fan selection range—
00.5"1.0"1.5"2.0"+
Supply Duct System
Supply ducts—
Diffusers / registers—
Coils & Filtration
Cooling coil—
Heating coil—
Pre-filter (MERV 8)—
Final filter (MERV 13-14)—
OA & Dampers
OA louver + screen—
OA damper—
Mixing box—
Return Side
Return ducts—
Return grilles—
Special
ERV—
HEPA—
Misc—
Total ESP—

📚 Typical Total ESP by System Type

System TypeTypical ESPNotes
Small residential / packaged0.3–0.6"Simple filter, short duct runs
Commercial VAV with MERV 131.5–2.5"Full AHU with cooling + heating coil
Lab / clean room AHU2.5–5.0"HEPA + ERV + multiple coils
100% OA DOAS unit1.5–3.0"ERV + coil + high OA fraction
Fan coil unit (FCU)0.2–0.5"Minimal duct, coil only
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