Elevator Hoistway Pressurization Calculator

Calculator

Input unit set

Target pressure (Pa)

Number of hoistways

Floors served per hoistway

Doors per floor

Closed door leakage each (cm²)

Other leakage per shaft (cm²)

Open doors during design

Open door width (m)

Open door height (m)

Open door area used (%)

Hoistway height (m)

Shaft plan area each (m²)

Inside Temperature (°C)

Outside Temperature (°C)

Wind speed (m/s)

Wind pressure coefficient

Air density (kg/m³)

Discharge coefficient

System static pressure (Pa)

Fan efficiency (%)

Airflow safety allowance (%)

Motor power allowance (%)

Formula Used

The calculator uses an orifice leakage method.

Q = Cd × A × √(2 × ΔP / ρ)

Q is airflow in m³/s. Cd is discharge coefficient. A is effective leakage area in m². ΔP is adjusted pressure in Pa. ρ is air density in kg/m³.

Adjusted pressure = target pressure + stack allowance + wind allowance

Stack allowance = ρ × g × H × |Tin - Tout| / TinK

Wind allowance = 0.5 × ρ × V² × |Cp|

Fan power = Q × total pressure / fan efficiency

How to Use This Calculator

Select the input unit set.
Enter the target pressure difference.
Add hoistway count, floors, and door count.
Enter closed door leakage and other leakage areas.
Add open door assumptions if needed.
Enter height, temperatures, wind speed, and fan data.
Press the calculate button.
Download the CSV or PDF report for records.

Example Data Table

Scenario	Target Pressure	Floors	Door Leakage Each	Other Leakage	Safety Allowance
Low-rise office	35 Pa	6	90 cm²	500 cm²	15%
Mid-rise apartment	50 Pa	12	116 cm²	775 cm²	20%
High-rise tower	60 Pa	30	140 cm²	1200 cm²	25%

Understanding Hoistway Pressurization

Elevator hoistway pressurization helps limit smoke movement during a fire. A fan supplies air into the shaft. The added air raises shaft pressure above nearby spaces. This pressure difference pushes smoke away from elevator doors and cracks. The exact design still needs local code review. This tool gives an estimating method for early design checks.

Why Leakage Matters

Airflow demand depends on leakage area. Closed elevator doors leak through gaps. Construction joints also leak. Open doors create a much larger path. The calculator combines door leakage, other leakage, and optional open door area. It then applies an orifice flow equation. Larger areas need more supply air. Higher pressure targets also increase airflow.

Pressure Effects

A shaft is tall. Temperature differences can create stack pressure. Wind can also push or pull on the building envelope. These effects may reduce useful pressurization. The calculator adds stack and wind allowances to the selected target. This makes the estimated fan duty more conservative. Designers may adjust each value after testing or simulation.

Fan Power Estimate

The tool estimates fan power from airflow and total pressure. Total pressure includes the pressurization duty and system static pressure. Fan efficiency is applied. A motor safety allowance is then added. This helps select a preliminary fan size. The result should not replace final fan curves, balancing data, or smoke control commissioning.

Design Use

Use measured leakage data when available. If it is not available, use conservative assumptions. Review door counts, hoistway height, and expected open doors. Compare airflow in cubic feet per minute and liters per second. Check air changes when the shaft plan area is entered. Save the result as a CSV or PDF for design notes. Recalculate after architectural changes. Document each assumption. Keep separate notes for normal power, emergency power, and control sequences before final review starts. Shafts, lobbies, relief openings, and controls can change the required airflow quickly.

Important Limits

This calculator is an estimator. It does not certify code compliance. Final systems may require fire modeling, stair and lobby interaction checks, damper sizing, relief paths, pressure sensor locations, and acceptance testing. Always coordinate with the authority having jurisdiction, fire protection engineer, mechanical engineer, elevator consultant, and commissioning team before construction.

FAQs

What is elevator hoistway pressurization?

It is a smoke control method. A fan supplies air into the hoistway. This creates positive pressure. The pressure helps resist smoke movement through doors, cracks, and shaft openings.

Is this calculator suitable for final design?

No. It supports early estimating and review. Final design should follow local codes, fire protection guidance, manufacturer data, and acceptance testing requirements.

What leakage area should I enter?

Use tested leakage data when possible. If that is not available, use conservative door gap estimates and include construction leakage. Larger leakage areas increase required airflow.

Why does stack pressure matter?

Stack pressure comes from height and temperature differences. It can push air up or down the shaft. This can reduce useful pressure at some floors.

Why include wind pressure?

Wind can add pressure to one side of a building. It can also pull air from another side. A wind allowance gives a more conservative fan estimate.

What is the discharge coefficient?

It adjusts ideal orifice flow for real leakage paths. Cracks, joints, and door gaps do not pass air perfectly. A value near 0.60 to 0.70 is often used for estimates.

What does safety allowance mean?

It adds extra airflow above the base leakage result. It helps cover uncertainty in leakage, field conditions, balancing, and future design changes.

Can I export the result?

Yes. Calculate first. Then use the CSV or PDF button. The export includes pressure, airflow, leakage area, and fan power results.