Horse-barn fans should be sized from combined horse weight and seasonal ventilation demand, not from stall count alone. A 1,000-pound horse and a 1,600-pound draft cross do not create the same design load, and a winter moisture-control rate is nowhere near a hot-weather heat-removal rate.

The University of Minnesota Extension gives three useful mechanical-ventilation benchmarks: 25 CFM per 1,000 pounds of horse in cold weather, 125 CFM per 1,000 pounds in mild weather, and 325 CFM per 1,000 pounds in hot weather. Those are total seasonal rates, not three interchangeable “recommended fan sizes.” Read the University of Minnesota’s horse-barn ventilation guidance.

Quick answer

  1. Add the body weight of the horses normally inside the barn at one time.
  2. Multiply the combined weight in thousands of pounds by the seasonal CFM rate: 25, 125, or 325.
  3. Divide the required CFM by the fan’s published CFM and round up to a whole fan where mechanical exhaust is appropriate.
  4. Size and distribute fresh-air inlets with the exhaust capacity. A fan without a planned inlet path can create negative pressure without giving every stall fresh air.
  5. Decide whether the barn is actually closed and mechanically ventilated. If large doors and windows are open, circulation fans and natural airflow become part of a different system.

This is an equipment-screen estimate, not a building design or a guarantee of cooling at the horse’s head. Static pressure, shutter condition, inlet area, dust, wiring, controller compatibility, and the fan curve still matter.

Interactive sizing tool

Estimate horse barn exhaust CFM

Enter the horses' combined weight, choose the season, and add the rated CFM of a fan you are considering. The result is a mechanical-ventilation starting point, not a promise of delivered airflow through a dirty shutter, restricted inlet, or poorly sealed barn.

Count the horses that are normally inside the ventilated barn at the same time.
Use the estimated total weight of all horses, not the weight of the largest horse alone.
Use the highest normal seasonal load you want the mechanical system to handle.
Use the product's published CFM as a comparison input; real installed airflow can be lower.
Open doors and windows change the airflow system. A circulation fan can create a breeze, but it does not replace fresh-air exchange.

Your CFM starting point

Enter the barn inputs to see a seasonal exhaust target.

The seasonal rates follow the University of Minnesota Extension: 25, 125, or 325 CFM per 1,000 lb of horse. Penn State Extension uses the same horse-weight benchmarks and recommends sizing inlets as part of the system.

The horse-barn CFM targets: cold, mild, and hot weather

The Minnesota benchmark is expressed per 1,000 pounds of horse because animal weight is a better sizing input than the number of stalls. The table below turns it into a practical first screen.

Seasonal conditionTotal exhaust targetMain job of the air exchangeExample for 4 × 1,000-lb horses
Cold weather25 CFM per 1,000 lbRemove moisture and reduce condensation, odors, and stale air100 CFM
Mild weather125 CFM per 1,000 lbKeep minimum exchange while removing transitional heat500 CFM
Hot weather325 CFM per 1,000 lbRemove heat with the barn operating as a mechanical system1,300 CFM

The mild and hot values are totals. The University of Minnesota describes mild weather as an additional 100 CFM per 1,000 pounds on top of the 25 CFM cold-weather rate, and hot weather as another 200 CFM on top of the mild-weather total. This is why “one fan per stall” is not a useful universal rule.

The formula

Required exhaust CFM = combined horse weight ÷ 1,000 × seasonal CFM rate

For six horses with an estimated combined weight of 7,200 pounds:

Cold:  7.2 × 25  = 180 CFM
Mild:  7.2 × 125 = 900 CFM
Hot:   7.2 × 325 = 2,340 CFM

The result is the capacity the mechanical system should be able to deliver at the chosen operating point. It does not mean that a 2,340-CFM product-page number will deliver 2,340 CFM after a dirty shutter, a restricted inlet, or a long duct path reduces airflow.

Horse count, combined weight, and the right design point

Horse count is still useful because it tells you how many animals share the air space, how many stall-level inlets need attention, and how many occupants may be present during the warmest part of the day. It just should not be the only input.

Use a reasonable estimate of each horse’s current body weight, add those estimates, and update the total if the herd changes. A barn with four 900-pound horses has a 3,600-pound design load; four 1,300-pound horses have a 5,200-pound load. At the hot-weather benchmark, those totals correspond to about 1,170 CFM and 1,690 CFM respectively.

When the barn also houses foals, ponies, draft horses, or unusually large warmbloods, use the actual combined total rather than an “average horse” shortcut. If you are uncertain, choose a transparent planning assumption, document it, and leave enough control range or staged capacity to handle the next season.

Mechanical exhaust versus an open barn

The calculator’s CFM output is for a barn that is operating as a mechanical ventilation system: exhaust fans remove air, fresh air enters through deliberate openings, and the building is closed enough for the airflow path to be predictable.

The exhaust fan is only half of that system. The University of Minnesota says well-distributed inlets prevent stagnant spaces and that each box stall should have an inlet near it. Penn State Extension gives a useful planning check of about 1.7 square feet of free inlet area per 1,000 CFM of fan capacity. The actual opening still needs to suit the building, wind exposure, screens, shutters, and the fan’s operating pressure.

An open or naturally ventilated barn is different. Large doors and windows can supply more air than the exhaust fan, and once those openings are open, the exhaust fans no longer provide the same mechanical air-exchange benefit. The University of Minnesota recommends turning them off in that situation and using circulation or mixing fans only to move air over the horses. A circulation fan creates a breeze; it does not bring new air into a closed stall.

This distinction prevents a common mistake: placing a large circulation fan in the aisle, feeling moving air there, and assuming the stalls have received the required fresh-air exchange.

How many fans do you need?

Once you have the required CFM, use the published fan rating as a comparison point:

Fan count = ceiling(required exhaust CFM ÷ one fan’s rated CFM)

For example, a 7,200-pound group at the hot-weather target needs about 2,340 CFM. A 4,244-CFM fan appears to clear that capacity screen with one unit. That does not automatically make one fan the best layout: the fan may serve only part of the barn, the stalls may not have enough inlet area, and the product’s CFM may be measured at a condition that does not match the installed wall.

Multiple smaller fans can make staging easier. A low-capacity fan can run for cold-weather moisture control, a second stage can engage in mild weather, and a higher stage can run in hot weather. This follows the seasonal logic in the Minnesota guidance and can be more useful than running one oversized, single-speed fan continuously.

Leave room for inlet area

Using the Penn State planning check, a 2,340-CFM mechanical system needs roughly:

2.34 × 1.7 square feet = about 4.0 square feet of free inlet area

“Free” matters. A nominal vent opening can lose useful area to mesh, louvers, dust, insulation, or a narrow path behind a shutter. Keep inlets spread across the horse area, make sure each stall has access to fresh air, and inspect them at the same time as the fan shutters.

Why a product’s CFM number is not the whole answer

CFM values are useful for comparing products within a sizing screen, but they are not interchangeable test results. Before accepting a product-page number, check:

  • Static pressure: A fan that moves a stated volume in free air may move less through a restrictive opening, screen, duct, or louver.
  • Air path: Exhaust should pull stale air from the horse area and draw fresh air across the stalls rather than short-circuiting from a nearby open door.
  • Shutters and guards: Dust, chaff, cobwebs, rust, and a shutter that cannot open fully can reduce airflow and create motor load.
  • Control range: A variable-speed fan may not deliver a published full-speed CFM at every dial position. A controller also cannot make an undersized fan large enough for hot weather.
  • Power and installation: Voltage, amperage, breaker sizing, weather exposure, wall framing, and the rough opening belong in the purchase decision.

If the barn smells strongly of ammonia, develops condensation, or feels hot in the stalls while the aisle feels comfortable, measure the airflow path before buying a larger fan. The problem may be an inlet or distribution fault rather than a lack of motor capacity.

Fans and controllers to compare after the calculation

Horse-barn exhaust fans and compatible control options

Product Best useListed airflowControlPower / fit Product page
iLIVING ILG8SF20V-ST 20-Inch Shutter Exhaust Fan iLIVING A 20-inch wall shutter fan with listed 3,368 CFM airflow, automatic aluminum shutters, and an integrated Thermospeed temperature and variable-speed controller.
  • 3,368 CFM listed airflow for capacity comparison
  • Integrated Thermospeed temperature and variable-speed control from 32–130°F
  • Automatic aluminum shutters and UL/cUL listing stated by iLIVING
 A compact, temperature-controlled exhaust starting point for a smaller mechanically ventilated barn 3,368 CFM listed Integrated Thermospeed temperature + variable-speed control; 32–130°F 115 V / 2.2 A / 0.2 HP Check current price on Amazon →
iLIVING ILG8SF24V 24-Inch Variable-Speed Shutter Exhaust Fan iLIVING A 24-inch variable-speed shutter fan with listed 4,244 CFM airflow, automatic shutters, corrosion-resistant construction, and a controller sold separately.
  • 4,244 CFM listed airflow and automatic shutters
  • Variable-speed motor intended for a compatible iLIVING controller
  • 120 V, 1/4 HP, and 2.75 A specification listed by iLIVING
 A mid-size wall fan when you want to select a separate speed or temperature controller 4,244 CFM listed Variable-speed motor; compatible controller sold separately 120 V / 1/4 HP / 2.75 A Check current price on Amazon →
iLIVING ILG8SF30V-T 30-Inch Two-Speed Exhaust Fan iLIVING A 30-inch wall shutter fan with listed 5,088 CFM airflow, two speeds, automatic shutters, and an adjustable built-in thermostat.
  • 5,088 CFM listed airflow with two-speed operation
  • Built-in 32–130°F capillary thermostat with bypass switch
  • Automatic aluminum shutters and enclosed motor design
 A larger closed barn where two-speed operation and an integrated thermostat can stage seasonal airflow 5,088 CFM listed Two speeds + built-in adjustable thermostat; 32–130°F 115 V / 1/3 HP / 3.1 A Check current price on Amazon →
iLIVING ILG8SF36S 36-Inch Single-Speed Shutter Exhaust Fan iLIVING A 36-inch wall shutter fan with listed 6,128 CFM airflow, automatic aluminum shutters, and a 120-volt 1/2-HP motor.
  • 6,128 CFM listed airflow
  • Single-speed operation with automatic aluminum shutters
  • 120 V, 1/2 HP, 6.0 A, and 825 RPM specification listed by iLIVING
 A high-capacity single-speed exhaust reference for a large barn with a separately designed electrical and control system 6,128 CFM listed Single speed; control gear must be designed for the exact motor 120 V / 1/2 HP / 6.0 A / 825 RPM Check current price on Amazon →
VEVOR AMX-FAG36 36-Inch Shutter Exhaust Fan, 11,000 CFM VEVOR A 36-inch steel shutter exhaust fan with listed 11,000 CFM airflow, automatic louvers, and a fan-only configuration in the selected listing.
  • 11,000 CFM, 120 V AC, 405 W, and 760 RPM listed by VEVOR
  • Automatic louvers and Q235B carbon-steel construction
  • A high-capacity reference for large mechanical-exhaust layouts
 A high-CFM comparison point for a large, closed barn after the inlet and installation design is complete 11,000 CFM listed Fan-only configuration; no bundled controller 120 V AC / 405 W / 760 RPM Check current price on Amazon →
iLIVING ILG8SFST Thermospeed Temperature and Speed Controller iLIVING A plug-and-play iLIVING controller with an NTC temperature sensor, automatic on/off cycling, and solid-state full-range speed control.
  • Temperature and speed control with automatic on/off cycling
  • NTC temperature sensor and solid-state full-range speed control
  • 120 V, 3 A FLA, 18 A LRA, and UL listing stated by iLIVING
 Automatic temperature cycling and variable-speed control for compatible iLIVING fans from 7 to 24 inches Controller only; it does not add fan CFM Temperature cycling + full-range variable-speed control 120 V / 3 A FLA / 18 A LRA Check current price on Amazon →
iLIVING ILG8SFRC Smart Remote Thermostat, Humidistat, and Timer Kit iLIVING A controller kit with a programmable thermostat, humidistat, timer, dual temperature sensing, and low/medium/high or automatic speed control.
  • Automatic cycling by temperature or humidity plus a 24-hour timer
  • Receiver and remote with dual temperature sensors
  • Solid-state speed control and up to 1,000 feet of control range stated by iLIVING
 Programmable temperature, humidity, timer, and remote control on compatible iLIVING variable-speed fans Controller only; it does not add fan CFM Temperature, humidity, timer, remote, and L/M/H or automatic speed 120 V / 3 A FLA / 18 A LRA Check current price on Amazon →
iLIVING ILG8SFSC Solid-State Variable Speed Controller iLIVING A rotary solid-state controller with on/off function, a single-gang wall-plate format, and an 8-amp 120-volt rating.
  • Rotary speed adjustment with on/off function
  • 120 V and 8 A rating stated by iLIVING
  • Fits a standard single-gang box and is UL listed
 Simple wall-mounted speed adjustment for a compatible iLIVING variable-speed shutter fan Controller only; it does not add fan CFM Rotary solid-state variable-speed control with on/off 120 V / 8 A Check current price on Amazon →

Use the linked US product page to confirm the exact model, package, electrical requirements, compatible controller, and installation details before purchasing. Marketplace configurations can change.

Affiliate links: We may earn a commission from purchases made through these links, at no extra cost to you.

These are comparison points, not a ranked “best fan” list. The iLIVING products make compatibility information easier to follow because the manufacturer documents which controllers work with variable-speed models and which do not work with single-speed fans. The VEVOR 36-inch product is a high-CFM reference point, but its selected configuration is fan-only, so do not infer controller compatibility from a marketplace title.

iLIVING 20-inch ILG8SF20V-ST: built-in temperature and speed control

Check current price on Amazon →

The 20-inch ILG8SF20V-ST is a useful small-to-mid-size comparison when the barn needs a wall-mounted exhaust fan with a temperature and speed control already integrated. iLIVING lists 3,368 CFM, a 115-volt 2.2-amp motor, automatic aluminum shutters, and a 32–130°F Thermospeed range. The product is listed as UL/cUL certified on the manufacturer page.

For a 4,000-pound group, 3,368 CFM is well above the 1,300-CFM hot-weather benchmark on paper. That is not a reason to run the fan at full speed all year. It is a reason to ask whether the fan can be staged or controlled at the required operating point, whether the inlets can support that capacity, and whether the installed airflow reaches the stalls.

The main limitation is scale. A 3,368-CFM unit can be a sensible starting category for a smaller barn, but it should not be treated as a universal answer for a long, closed aisle with many large horses. If the product’s controller is used, set it around the ventilation plan—not simply around a comfortable temperature in the aisle.

iLIVING 24-inch ILG8SF24V: flexible mid-size fan with a separate controller

Check current price on Amazon →

The 24-inch ILG8SF24V is the flexible middle option in this comparison. iLIVING lists 4,244 CFM, a 120-volt 1/4-HP motor, automatic shutters, corrosion-resistant construction, and a variable-speed motor intended to work with a separate ILG8SFSC controller. The official product information describes hardwired installation, so plan the electrical work and the wall opening instead of assuming a plug-in package.

For an owner who wants simple manual speed adjustment, the iLIVING ILG8SFSC speed controller is the relevant accessory family. For automatic temperature cycling, the iLIVING ILG8SFST Thermospeed controller is the more direct fit for compatible iLIVING variable-speed fans from 7 to 24 inches. The Thermospeed controller is not for single-speed fans.

The strength of this pairing is control range. The limitation is that a separate controller adds another compatibility and installation check, and the fan’s 4,244-CFM headline still does not size the inlets or prove delivered airflow in the finished barn.

iLIVING 30-inch ILG8SF30V-T: two-speed thermostat stage

Check current price on Amazon →

The 30-inch ILG8SF30V-T is a larger wall-exhaust option with a built-in adjustable thermostat and two-speed operation. iLIVING lists about 5,088 CFM, 115 volts, a 1/3-HP motor, automatic shutters, a six-foot power cord, and a 32–130°F thermostat range.

This is a practical match when the CFM calculation suggests a meaningful mild-to-hot step-up and you want a control layer included with the fan. It is not a substitute for a multi-stage barn design: one large fan may still leave far stalls without a good air path, and a thermostat in the wrong part of the building can respond to the aisle rather than the horse area.

Do not connect the 30-inch fan to the small iLIVING Thermospeed controller simply because both products mention “temperature.” The manufacturer’s compatibility information for that controller is limited to compatible variable-speed iLIVING fans up to 24 inches, while the 30-inch model has its own control arrangement.

36-inch options: iLIVING single-speed versus VEVOR high-CFM

The iLIVING ILG8SF36S 36-inch fan is a single-speed, automatic-shutter fan listed at 6,128 CFM with a 120-volt, 1/2-HP motor and 6-amp draw. It is a straightforward high-capacity wall-exhaust reference when a qualified installer is designing the control and electrical system around it.

The VEVOR AMX-FAG36 36-inch fan is a higher-CFM comparison point. VEVOR lists 11,000 CFM, 120V AC, 405W, 760 RPM, automatic louvers, steel construction, and a fan-only configuration. That capacity can be relevant to a large closed barn, but it raises the importance of a properly framed opening, adequate inlets, animal-safe guarding, circuit design, and a control plan.

Do not add a generic speed dial to a single-speed 36-inch fan without confirming the motor and controller compatibility. A product listing that mentions variable speed for another size or variant is not proof that the selected fan can be controlled that way.

Controllers: temperature, humidity, timer, or simple speed?

The iLIVING ILG8SFRC smart remote kit adds programmable temperature and humidity control, a timer, dual temperature sensing, and low/medium/high or automatic speed control for compatible iLIVING variable-speed fans. iLIVING explicitly excludes single-speed models such as the 36-inch ILG8SF36S from this controller family.

The iLIVING ILG8SFSC is simpler: a wall-mounted rotary speed controller for compatible variable-speed fans. It does not create an automatic seasonal plan, measure barn humidity, or fix an airflow shortage. Choose the control function that matches the fan motor and the barn’s operating sequence, then verify the wiring with a qualified professional.

Installation and horse-barn safety checklist

Penn State Extension warns that horse barns carry more dust, chaff, moisture, odor, mold, and manure-related air contaminants than a typical home. It also recommends agricultural-rated fans with enclosed or sealed motors rather than cheap residential stall fans whose motors can collect dust and ignite.

Before installation, check the following:

  • Fan location: Mount the exhaust fan out of the horse’s reach and where the airflow path serves the horse area, not only the aisle.
  • Fresh-air inlets: Provide distributed, year-round access to outside air for each stall. Do not reduce the inlet to a small, dust-clogging residential screen.
  • Motor and guard: Use an agricultural or suitably rated fan with a proper guard, thermal protection, and a shutter that can open fully.
  • Electrical work: Match voltage, amperage, disconnect, breaker, conduit, and weather protection to the installation. Do not use an extension cord as a substitute for fixed barn wiring.
  • Dust maintenance: Turn power off before cleaning. Remove dust, chaff, cobwebs, and nesting material from the fan, motor area, controller, and inlets on a scheduled basis.
  • Controller fit: Confirm that the controller is rated for the exact motor type and that its temperature sensor represents the horse area rather than a warm ceiling or sunny wall.
  • Wall opening and drainage: Follow the fan manual for the rough opening, framing, shutter clearance, rain exposure, and service access.

The Penn State fire-prevention guidance for equine facilities specifically calls out dust around unsealed fan motors, damaged cords, and the need for agricultural-rated fans. The University of Minnesota’s barn-disaster guidance likewise advises maintaining ventilation motors, keeping hay away from wiring, and never overloading circuits.

A simple seasonal operating plan

Cold weather: maintain the minimum exchange

The cold-weather target is modest because the main job is moisture control, not cooling. The University of Minnesota describes continuously running sidewall exhaust fans as the best cold-air exchange in a mechanical system. Keep fresh-air inlets available and avoid aiming a cold jet directly at a horse. Fresh air should mix before it reaches the stall occupant.

Watch condensation on ceilings, walls, windows, and metal fittings. A barn that feels warm but holds moisture is not well ventilated, and closing every opening to preserve heat can worsen air quality.

Mild weather: add a second stage or a higher setting

Mild weather needs the 125-CFM total target. This is where a controller or staged fan setup becomes useful: the low stage can handle moisture while a second stage removes transitional heat. The Minnesota guidance uses an indoor setting around 50°F as an example for the mild-weather stage, but the correct sensor location, building, horse population, and weather pattern still need observation.

Hot weather: use the maximum mechanical rate only in the right system

Hot weather needs the 325-CFM total target when the barn is operating as a closed mechanical system. The Minnesota guidance describes another exhaust stage and a separate controller activating around 60°F to help stop the temperature from rising. A fan can support air exchange and air movement, but it cannot replace shade, water, turnout decisions, or veterinary attention for a horse showing heat stress.

If the barn is opened widely for natural ventilation, reassess the system instead of leaving all exhaust fans on automatically. The exhaust fan may no longer improve the exchange rate, while circulation fans can be used to create a cooling breeze over the horse.

Three worked sizing examples

Two 1,000-pound horses

Combined weight is 2,000 pounds:

  • Cold: 50 CFM
  • Mild: 250 CFM
  • Hot: 650 CFM

A 3,368-CFM wall fan is much larger than the hot-weather capacity screen for this pair. That can be workable only if the motor/control setup permits a suitable lower operating point and the inlet path is designed accordingly. A single-speed fan that cannot be staged may be a poor match even when its headline CFM is more than enough.

Four 1,000-pound horses

Combined weight is 4,000 pounds:

  • Cold: 100 CFM
  • Mild: 500 CFM
  • Hot: 1,300 CFM

A 4,244-CFM variable-speed fan clears the hot-weather capacity screen on paper. The choice now depends on whether it can be controlled safely, whether the inlets provide enough free area, and whether the fan serves all four stalls rather than short-circuiting to a nearby door.

Twelve 1,000-pound horses

Combined weight is 12,000 pounds:

  • Cold: 300 CFM
  • Mild: 1,500 CFM
  • Hot: 3,900 CFM

One 5,088-CFM two-speed fan has enough listed capacity for this simplified screen, but layout becomes more important as the barn gets longer. Two staged fans may distribute air better, provide a lower cold-weather stage, and give the operator a fault-tolerant way to keep some exchange running during service.

What to check after the fan is installed

Do not stop at “the blades are turning.” Walk the stalls and check the result at the horse’s breathing zone and near the floor where dust and ammonia can collect.

  1. Confirm that all shutters and inlets open fully when the fan runs.
  2. Look for a clear path from each fresh-air inlet across the stall area to the exhaust.
  3. Compare the aisle with the farthest stalls; a comfortable aisle does not prove good stall ventilation.
  4. Check for condensation, persistent odor, dust accumulation, or hot, still pockets.
  5. Clean the fan and inlets, then repeat the check before increasing fan size.
  6. If the motor overheats, the breaker trips, the controller cycles unexpectedly, or the barn develops strong ammonia odor, stop treating the issue as a simple CFM shortage and bring in a qualified electrician, agricultural ventilation professional, or veterinarian as appropriate.

Frequently Asked Questions

How many CFM does one horse need in a barn?

There is no single all-season number. The University of Minnesota benchmark is 25 CFM per 1,000 pounds in cold weather, 125 CFM per 1,000 pounds in mild weather, and 325 CFM per 1,000 pounds in hot weather for a mechanical system. A 1,000-pound horse therefore screens at 25, 125, or 325 CFM depending on the season and the operating mode.

Is 3,000 CFM enough for four horses?

For four 1,000-pound horses, the hot-weather benchmark is 1,300 CFM, so 3,000 CFM clears the simple capacity screen. It may still be a poor installed system if the fan is single-speed, the inlets are too small, the shutters are dirty, or the air does not reach the stalls. Use the CFM result together with the inlet and control checks.

Should I use a circulation fan or an exhaust fan?

Use an exhaust fan when the goal is mechanical air exchange through a planned inlet path. Use a circulation or mixing fan when the barn is naturally open and the goal is a cooling breeze. A circulation fan does not replace fresh-air exchange in a closed stall.

Should a horse-barn exhaust fan run in winter?

A mechanical system still needs minimum winter exchange for moisture and stale-air control. The Minnesota guidance uses 25 CFM per 1,000 pounds and describes continuously running sidewall exhaust as the best cold-weather exchange. Keep the inlet path mixed and draft-safe, and follow the fan/controller manual rather than turning off all ventilation whenever the temperature drops.

Can I put a thermostat controller on a 36-inch fan?

Not automatically. The iLIVING ILG8SFST and ILG8SFRC controller families are documented for compatible variable-speed iLIVING fans and exclude single-speed models, including the iLIVING 36-inch ILG8SF36S. Match the exact motor and control specification; never rely on a generic dial because the plug or voltage happens to fit.

Does a larger fan guarantee a cooler horse?

No. A larger fan can increase capacity, but poor inlets, short-circuiting air, high humidity, shade limitations, limited water access, or a horse that is already overheating can still create a welfare problem. CFM is a ventilation design input, not a diagnosis or a complete heat-stress plan.

Bottom line

Start with the combined weight of the horses, not the number of stalls. Use 25 CFM per 1,000 lb in cold weather, 125 CFM in mild weather, and 325 CFM in hot weather as a transparent mechanical-ventilation screen. Then round up to a practical fan arrangement, size the inlets, choose a controller that actually matches the motor, and confirm the airflow in the stalls after installation.

The right fan is the one that fits the whole air path: clean, distributed inlets; safe agricultural-grade equipment; correct electrical work; seasonal control; and enough delivered airflow where the horses breathe.

Sources and further reading