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Mechanical / HVACaka: exhaust ventilatoraka: toilet exhaust fanaka: kitchen exhaust fan

Exhaust Fan

In Plain English

A fan that removes stale air, odors, or pollutants from a room and exhausts them to the outside.

Definition

A mechanical fan that removes air, heat, odors, contaminants, or moisture from a space to the exterior of the building. Exhaust fans are used in restrooms, kitchens, laboratories, parking garages, and other areas requiring positive ventilation. They may be wall-mounted, ceiling-mounted, or roof-mounted and must be coordinated with makeup air supply to maintain proper building pressurization.

Why It Matters in Bidding

Exhaust fans are easy to under-scope because the unit cost is small but the associated ductwork, roof penetrations, makeup air, controls interlocks, and electrical connections carry most of the labor and material dollars. Estimators who price only the fan and miss the makeup air coordination or code-required CFM rates risk negative pressurization issues, change orders, and rejected commissioning.

Example

While taking off a restaurant tenant build-out, the mechanical estimator counts six restroom and hood exhaust fans, then prices the matching roof curbs, makeup air unit, and BAS interlock so the bid covers the full ventilation scope rather than just the fans.

Related Terms

Makeup Air UnitDuctworkAir HandlerHVAC

Frequently Asked Questions

Bidders frequently price the fan alone and overlook the roof curb, backdraft damper, ductwork, exterior cap or louver, makeup air provisions, line voltage wiring, and control interlocks. These supporting items often exceed the fan cost, so a clean takeoff lists each fan with its full installation assembly and the responsible trade.
Scope splits vary by spec. Mechanical typically furnishes and sets the fan, electrical pulls power and makes final connections, and controls or low-voltage handles interlocks and switching. Clarify the division in your bid notes or a scope-clarification RFI so no trade assumes another is carrying the wiring, avoiding gaps at award.
Large exhaust volumes must be balanced with tempered makeup air to keep the building from going negative, which causes door problems and combustion backdrafting. If the drawings require makeup air, the estimator must carry that unit, its heating source, and controls. Missing it is a common source of post-award change orders and commissioning failures.

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