Commercial Kitchen Hood Exhaust Calculator

Concepts behind this calculation

Check a CaptiveAire ND-2 catalog exhaust floor against actual nameplate flow, appliance layout, cooking temperatures and mounting limits.

This hood comparison uses a specific catalog profile rather than a general exhaust rate for every commercial kitchen. The selected configuration and temperature row establish a length-based catalog floor. The governing exhaust minimum is the largest of that floor, the actual assembly nameplate minimum and any additional project minimum. Back-to-back hoods use a common length per bank and combined assembly airflow.

Airflow is only one constraint on capture geometry. Each rear-aligned cooking surface has a position, width, depth and temperature, allowing the tool to check left, right and front overhangs as well as mounting and temperature limits. Every appliance must meet the selected temperature row; the tool does not average a hot appliance with cooler neighbors. Direct hood supply is assessed separately from whole-building replacement air.

How to use this calculator

1. Select ND-2 configuration and Selected catalog temperature row, then record the Model, nameplate and appliance reference and Any solid-fuel appliance status.
2. Enter Common hood length per bank, Hood coverage depth per bank, required overhangs, Cooking surface to hood lower edge and the documented mounting and temperature limits.
3. Supply the nameplate and project exhaust minimums, Proposed or measured exhaust airflow, and documented and proposed direct hood supply.
4. Enter Appliance rows with the correct bank and common rear reference; review individual margins rather than the exhaust total alone.

Calculation method and applicability

Catalog floor = common length in ft × ND-2 rate (150, 200 or 250 CFM/ft for single wall at 450, 600 or 700 °F; 300, 400 or 500 combined for back-to-back). Governing minimum = max(catalog floor, assembly nameplate minimum, project minimum). Left = min(start); right = hood length − max(start + width); front = coverage depth − max(appliance depth).

Input definitions and units

ND-2 configuration

Only the two configurations in the cited ND-2 table are supported. Back-to-back uses two equal-length banks and a combined flow. Choices: Single wall canopy; Two wall hoods back-to-back.

Selected catalog temperature row (°F)

Use the applicable documented row. The source heading says average cooking surface temperature; this conservative screen checks every appliance against the selected row and does not average appliance temperatures. Choices: 450 °F; 600 °F; 700 °F.

Model, nameplate and appliance reference

Required: exact model and assembly, source revision, applicable nameplate limits, appliance types and fuels, selected rating basis, supply accessory and cooking-surface rear reference. A text reference does not authenticate data.

Any solid-fuel appliance?

This implemented profile has no verified solid-fuel listing fixture; selecting yes withholds a numeric result. Choices: No; Yes — outside this profile.

Common hood length per bank (in.)

Use the documented available model length. Back-to-back banks must have the same length; do not add both lengths together.

Hood coverage depth per bank (in.)

Coverage depth measured from the same rear cooking-surface reference as the appliance depths. Not a combustible clearance or overall shipping dimension.

Required front overhang (in.)

Actual assembly nameplate or approved project requirement. The example 6 in is constructed and is not a universal ND-2 requirement.

Required overhang at each side (in.)

Same requirement applied to left and right of each bank; asymmetric requirements are outside this profile. The example value is constructed.

Cooking surface to hood lower edge (in.)

Vertical installed distance from cooking surface to the front lower edge. This is not height above the finished floor.

Documented minimum mounting clearance (in.)

Copy the actual assembly documentation or approved project range. Example 36 in is constructed, not a manufacturer default.

Documented maximum mounting clearance (in.)

Use the actual allowed upper bound. Example 48 in is constructed; the manual’s typical height above floor is not this clearance.

Nameplate maximum cooking temperature (°F)

Actual assembly limit checked separately from the catalog row. Every entered appliance must meet both limits.

Nameplate minimum exhaust for this assembly (CFM)

Actual selected assembly minimum. For back-to-back, enter the combined total for both banks, not a per-bank value.

Additional project exhaust minimum (CFM)

Same assembly and total-flow basis. Enter a higher approved project requirement where applicable; zero means no additional minimum entered.

Proposed or measured exhaust airflow (CFM)

Total delivered airflow for this assembly at the operating condition. The calculator does not solve the fan or duct system.

Documented maximum direct hood supply (CFM)

Applies to the actual hood supply accessory on the same total basis. Enter documented zero if none. Example 500 CFM is constructed; no universal supply percentage is assumed.

Proposed direct hood supply (CFM)

Supply through the documented hood accessory, not total building replacement air. Example 400 CFM is constructed.

Appliance rows: bank, start, width, depth, temperature (CSV)

One to 50 rows. Bank 1 for single wall; banks 1 and 2 required for back-to-back. Start, cooking-surface width and depth in inches; temperature in °F. Start is measured from the hood left edge. One nonoverlapping row per bank, all rear-aligned to the documented reference. Touching edges allowed.

How to interpret the result

Review the governing exhaust minimum alongside every bank’s geometry, cooking-temperature, mounting and direct-supply margins. A favorable entered-limits status does not establish field capture or resolve an unsupported hood or fuel configuration.

Worked examples

Assumptions and limits

• Only the cited ND-2 performance profile is implemented. Type II, proximity, other island hoods, other brands, unequal back-to-back banks and solid fuel are outside scope. No universal hood-length coefficient or duty-class substitution is used.
• The catalog heading uses average cooking surface temperature. This page requires every appliance to be no hotter than the selected row and nameplate limit; it does not average appliances or infer their duty classification. This conservative screen does not reproduce a listing test.
• Actual assembly availability, selected size, cooking equipment and accessories must be supported by the submittal. Catalog arithmetic does not establish that an arbitrary dimension or arrangement is a listed product.
• Geometry assumes one rear-aligned nonoverlapping cooking-surface row per bank. It does not handle offset backs, staggered rows, asymmetric side limits, cross-drafts or obstructions. Coverage dimensions are not clearance to combustibles.
• The manual requires actual nameplate information. Typical height above finished floor is not an allowed cooking-surface clearance range. Worked-example 6 in overhangs, 36–48 in mounting range and supply values are constructed, not copied nameplate specifications.
• No automatic end-panel discount, supply percentage, fan selection, grease duct sizing, fire suppression, building pressure balance, field capture test or current local-code approval is provided. Direct hood supply is distinct from whole-building makeup air.

Sources

• CaptiveAire ND-2 product profile and performance tablePerformance table on PDF page 2 provides the named temperature/configuration rates. Page 1 gives the 4 ft, 150 CFM/ft, 600 CFM benchmark. No dimension-specific nameplate is supplied by this brochure.
• CaptiveAire hood installation, operation and maintenance manualPage 9 requires nameplate clearance, minimum exhaust, maximum supply, front and side overhangs and cooking temperature. Its typical height above floor is not a generic permissible cooking-surface range.
• Greenheck canopy hood installation manualIndependent manufacturer context for nameplate-based installation constraints; no Greenheck flow coefficient is transferred into the ND-2 calculation.