Poultry House Ventilation Equipment: Sizing and Layout

বায়ু চলাচল sizing starts with house volume and target hen weight, not fan brand. Tunnel systems suit houses roughly 40 ft (12 m) and wider, aiming for 350–800 ft/min air speed; cross ventilation fits narrower houses or cooler climates. Fan capacity, pad area, and inlet sizing all scale off the same cross-sectional airflow number.

Most commercial-scale RFPs specify total bird capacity and house count but leave ventilation as “adequate mechanical ventilation to be provided” — a phrase that gives a contractor no design target. The steps below turn a house footprint and a target bird weight into fan count, pad area, and an inlet plan a project engineer can check against.

Step 1: Establish House Volume and Ventilation Stages

Start with the physical envelope, not the bird count.

1. Record house length, width, and average interior height (sidewall height plus roof pitch allowance) in feet or meters.
2. Calculate house volume: length × width × average height.
3. Separate the ventilation requirement into stages — minimum ventilation (cold weather, moisture and air-quality control), transitional ventilation (mild weather), and tunnel or full ventilation (heat stress conditions). Each stage uses a different fan set, not the same fans running at partial speed.
4. Confirm the design temperature range for the project site. Coastal Southeast Asia and interior Southern Africa call for different tunnel-stage targets even at the same house width.

Skipping stage separation is the most common design shortcut on smaller projects — it leaves a single fan bank trying to do both jobs, which oversizes cold-weather ventilation or undersizes hot-weather cooling.

Step 2: Choose Tunnel or Cross Ventilation

House width and climate decide this before cost does.
টানেল বায়ুচলাচল banks fans at one end wall and pulls air the length of the house, producing the air speed needed for wind-chill cooling. According to University of Georgia Cooperative Extension research on broiler housing, air speeds of 350–400 ft/min have traditionally been used, but larger modern market-weight birds often require 600–800 ft/min to maintain the same cooling effect. Cross ventilation mounts fans along the sidewalls, moving air perpendicular to the house length; it depends on house-wide air exchange rather than wind-chill speed and is generally easier to control in narrower or cooler-climate houses, though it will not reach tunnel-level air speeds in wide layouts.
A rough decision rule: below about 30–40 ft (9–12 m) of house width or in climates where summer heat stress is not the dominant design constraint, cross ventilation is usually sufficient and cheaper to control. Above that width, or in projects where peak-season heat stress drives bird performance, tunnel ventilation with pad cooling becomes the standard design.

Step 3: Size Fan Capacity Against Cross-Section

This is arithmetic, and it is where undersizing usually happens.

1. Calculate the house cross-sectional area: width × average height (in square feet).
2. Multiply by the design air speed target (350–800 ft/min, from Step 2) to get total required cubic feet per minute (CFM).
3. Divide total required CFM by each fan’s rated capacity — but use the rating at 0.05 in. static pressure, not the fan’s free-air (0.00 in.) number. Auburn University’s Agricultural Extension program notes that fan CFM should be selected at 0.05 in. static pressure because that is the typical operating condition for tunnel ventilation; free-air ratings overstate real capacity.
4. Round the fan count up, not down — commercial tunnel fans on the market range roughly 16,000–24,000 CFM at that pressure point, and a shortfall of even one fan below the calculated total leaves the house under 400 ft/min in practice.

A worked example: a 60 ft × 400 ft house with a 10 ft average height has a cross-section of 600 sq ft. At a 600 ft/min design speed, that’s 360,000 CFM total. At roughly 20,000 CFM per fan (0.05 in. rating), the house needs 18 fans — not 15 or 16, which is where “close enough” fan counts tend to land on smaller budgets.

Step 4: Match Cooling Pad Area to Fan Capacity

Pad area is sized off fan capacity, not house floor area — a detail that gets confused often enough to cause real airflow problems.
University of Georgia Cooperative Extension’s published guidance sets the ratio at approximately 1 sq ft of 6-inch evaporative pad for every 350 CFM of tunnel fan capacity, or 1 sq ft of 4-inch pad for every 225 CFM. Using the 360,000 CFM example from Step 3: 360,000 ÷ 350 = roughly 1,030 sq ft of 6-inch pad, split across both sidewalls near the tunnel inlet end. Undersized pad area raises static pressure at the pad face, which reduces the very air speed the fans were sized to deliver — the fans keep running, but the house doesn’t cool as designed.

Step 5: Size and Position Air Inlets

1. Inlets and fans have to balance, or the pressure numbers in Step 6 won’t hold.
   Set inlet opening area so the house runs at negative pressure during minimum-ventilation stages — typically a narrow static pressure band the controller manages automatically once inlets are correctly sized.
2. For tunnel-stage operation, size tunnel curtain or door openings to avoid restricting the pad face; an undersized tunnel opening creates the same static pressure penalty as an undersized pad.
3. Distribute minimum-ventilation inlets evenly along both sidewalls rather than clustering them, to avoid drafts concentrated over part of the flock.
4. Where the project uses a solid-set steel structure house rather than curtain-sided construction, inlet placement has to be fixed at construction stage — this is a decision that has to be made with the building shell, not added afterward.

Step 6: Verify With a Static Pressure Check Before Commissioning

Design numbers on paper and measured performance in the finished house are two different things.
Measure static pressure at the fans once the house is buttoned up and all tunnel fans are running. Auburn’s Extension data on fan performance shows design static pressure running roughly 0.12–0.15 in. for a 600 ft/min house and 0.17–0.20 in. for an 800 ft/min house; a reading well outside that band signals an inlet, pad, or fan-count mismatch, not a fan-quality problem. The same research documented airflow losses of 20.7–27.0% from dirty intake shutters alone — a maintenance issue, not a design flaw, but one that erases a properly sized system’s margin if it isn’t checked.

Ventilation Design Reference Table

None of these figures are Mugong product specifications — they are industry category-reference values used to plan a system, shown here to distinguish design math from equipment claims.

Tunnel vs. Cross Ventilation at a Glance

Ventilation Checklist for Tender and RFP Documents

1. State target bird species, breed if known, and maximum market weight — fan and pad sizing scales directly off this.
2. Provide exact house width, length, and average interior height, not just floor area.
3. Require fan CFM quoted at 0.05 in. static pressure, not free-air rating, in supplier proposals.
4. Ask for the pad-area calculation method the supplier used, not just a finished pad dimension.
5. Request a post-installation static pressure commissioning report as a deliverable, not an assumption.
6. Confirm whether ventilation equipment is bundled into EPC turnkey scope or priced as a separate line item.

প্রায়শই জিজ্ঞাসিত প্রশ্নাবলী

 What’s the real difference between tunnel and cross ventilation?

Tunnel ventilation pulls air the length of the house at 350–800 ft/min for wind-chill cooling and pairs with evaporative pads in hot climates; cross ventilation moves air across the house width at lower speed and works well in narrower houses or milder climates without needing pad cooling.

 How do I calculate how many fans a broiler house needs?

Multiply house cross-sectional area (width × average height) by the target air speed to get total required CFM, then divide by each fan’s rated CFM at 0.05 in. static pressure — not the free-air rating.

 How much cooling pad area do I need per fan?

A commonly used industry ratio is 1 sq ft of 6-inch pad per 350 CFM of fan capacity, or 1 sq ft of 4-inch pad per 225 CFM, based on UGA Cooperative Extension design guidance.

 My house has enough fans on paper but still runs hot — why?

Undersized pad area, an undersized tunnel inlet, or dirty intake shutters can all raise static pressure enough to cut real fan output well below the nameplate CFM, even with a correct fan count.

 Does Mugong sell ventilation fans and pads as standalone equipment?

Ventilation is delivered as part of the Farm Support & Auxiliary Systems scope on full house and turnkey projects; the company does not publish a standalone fan/pad model number or price online, so sizing and quoting happen at the project-inquiry stage.

What static pressure should a properly sized tunnel house run at?

A: Roughly 0.12–0.15 in. for a 600 ft/min design speed and 0.17–0.20 in. for an 800 ft/min design speed, per UGA Cooperative Extension field data — readings well outside that range point to an inlet, pad, or fan-count mismatch.