Define The Boundary
State the design airflow, louver orientation, rain control, insect screen, filter, face velocity and allowable pressure. Check the path from outdoor opening to occupied zone, not only the louver catalog table.
Louver Size Follows The Replacement-Air Duty
Make-Up Air Louver Sizing
A louver is not sized by its outside dimensions alone. Net free area and pressure loss determine whether replacement air reaches the room without excessive noise or negative pressure.
DefineReal Duty
CheckComplete Path
SelectExact Model
VerifyInstalled Result
Direct Answer
What Is The Practical Method For Make-Up Air Louver Sizing?
A louver is not sized by its outside dimensions alone. Net free area and pressure loss determine whether replacement air reaches the room without excessive noise or negative pressure.
State the design airflow, louver orientation, rain control, insect screen, filter, face velocity and allowable pressure. Check the path from outdoor opening to occupied zone, not only the louver catalog table.
A louver can be physically large and still have restricted net free area. Louvers, filters, dampers and make-up fans must be included in the same pressure and interlock review as the exhaust fan. There is no universal make-up-air percentage. The correct balance depends on exhaust diversity, process capture, envelope leakage, door operation and the pressure target.
Engineering scope and sources reviewed 6 October 2026 · Project conditions still govern final selection
Decision Framework
Four Checks For Make-Up Air Louver Sizing
Keep the recommendation tied to a field decision and a measurable boundary.
Check The Whole Assembly
A louver can be physically large and still have restricted net free area. Louvers, filters, dampers and make-up fans must be included in the same pressure and interlock review as the exhaust fan.
Commission The Result
There is no universal make-up-air percentage. The correct balance depends on exhaust diversity, process capture, envelope leakage, door operation and the pressure target.
Keep Evidence
Record the assumptions, test condition, responsible reviewer and stop criteria so a later change does not erase the original decision.
Field Inputs
Inputs To Put In The Review Record
Use one row for every assumption that can change the answer.
| Record | What to capture | Why it matters |
|---|---|---|
| Design input | Document the measured or specified condition | A generic label does not define duty |
| Physical path | Check inlet, fan, outlet, supports and access | Local geometry can dominate the result |
| Control condition | Record speed, schedule, interlocks and alarms | The fan may not run at one fixed point |
| Verification | Measure airflow, pressure or the relevant acceptance signal | Running is not proof of performance |
| Change trigger | Define what requires a new review | Chemistry, layout and duty can change |
Boundary: The values and limits are project-specific. Confirm the exact equipment instructions, standards and responsible engineer before release.
Practical Sequence
Work Through Make-Up Air Louver Sizing In Six Steps
- State the job.Write the room or process objective, required airflow, pressure and the condition that must be controlled.
- Map the path.Mark source, inlet, fan, filters, dampers, duct, discharge, replacement air and service access.
- Check constraints.Review structure, materials, electrical supply, controls, safety classification, noise and maintenance.
- Select with evidence.Compare exact models at the same duty and disclose catalog, test and project assumptions.
- Install to instructions.Use the approved mount, guard, connection, clearance and control method for the equipment.
- Verify and record.Measure the relevant result, document the operating condition and set the next review trigger.
Connected Decisions
Use The Next Page Only When It Answers The Next Question
These links continue the same project workflow rather than sending the reader to loosely related content.
Size The Exhaust Duty
Start with required airflow, pressure and the actual air path before picking a series.
Measure The Installed Airflow
Use a repeatable field measurement when a symptom could be caused by the system rather than the fan.
Check System Effect
Short elbows, transitions, dampers and discharge restrictions can change the operating point.
Review Air-Make-Up
Replacement air and pressure balance belong in the same design conversation as exhaust.
Questions Buyers Actually Ask
Make-Up Air Louver Sizing Questions
What is the most important input for make up air louver sizing?
State the design airflow, louver orientation, rain control, insect screen, filter, face velocity and allowable pressure. Check the path from outdoor opening to occupied zone, not only the louver catalog table. The input should be written down before a model or setting is treated as final.
Can a catalog value prove the installed result?
No. Catalog values are screening evidence. Verify the actual operating condition, measurement method and system configuration before accepting performance.
What should I send for a project review?
Send the duty, air or process condition, layout, pressure assumptions, controls, power, environment, photos and any baseline measurements.
Is there one universal setting or size?
No. The correct value depends on the exact fan, building, air path, controls, environment and acceptance requirement.
When should the design be reviewed again?
Review it after a change in process, contaminant, temperature, layout, filter condition, duty, control sequence or observed performance.
How do I account for louver free area when sizing make-up air?
Convert the required airflow into a face velocity using the louver's published free area, then check rain, screen, filter and pressure-drop effects. The gross wall opening is not the same as the effective airflow area.
Source Boundary
References Used For This Guide
Sources define methods and safety boundaries. They do not certify a proposed AirMoveX model or replace the adopted code, OEM instructions or a qualified project designer.
AMCA International
AMCA Publications and Education
AMCA separates fan performance, system effects, sound and application conditions; use the applicable publication and test basis for a project decision.
Open sourceU.S. Department of Energy
Better Buildings and Industrial Systems
DOE guidance supports measured operating data, controls and whole-system comparisons rather than unsupported universal savings claims.
Open sourceOSHA
Safety and Health Regulations
Safe access, guarding, energy control and competent-person requirements remain site-specific and apply before field work.
Open sourceProject Review
Send The Inputs, Not Just The Fan Name
Share the building or process objective, airflow and pressure basis, air condition, layout, controls, power, access and existing measurements. AirMoveX can prepare a shortlist while keeping the assumptions visible.