Most poultry producers know the feeling. The days are getting longer, outside temps are creeping up, and somewhere between May and July, the way you manage your houses has to fundamentally change. Not just the settings. The entire logic behind what your ventilation system is trying to accomplish.
That shift is where a lot of operations quietly lose money, and most of the time they never see it coming.
Two Modes, Two Different Goals
Poultry house ventilation doesn’t operate on a single sliding scale from cool to hot. It operates in distinct modes, and the handoff between them is more abrupt than most producers realize.
In warm weather ventilation, your primary goal isn’t temperature. It’s air quality. As house temps rise above your set point, typically somewhere between 65 and 75°F depending on bird age, fans begin to run more frequently as fresh air moves consistently cross-wise through the barn via sidewall inlets. You’re managing moisture, ammonia, and CO₂ before heat becomes the dominant threat.
The critical thing to understand at this stage is that wind chill is your enemy. Running too many fans too early creates airspeed that causes birds to lose body heat faster than they should, forcing them to consume extra feed just to stay warm. Feed conversion ratios climb. Costs follow. It’s a subtle problem that rarely gets flagged because nobody is watching for it.
Hot weather ventilation flips the logic entirely. When outside temps push past roughly 77°F — or when your house simply can’t be managed transitionally anymore — the goal shifts from air quality to heat removal. Exhaust fans begin to run at maximum capacity. Air now travels at higher speeds (somewhere between 400 and 600 feet per minute at bird level) and any air leaks within the house begin to show. The house must be fully sealed, because any air leak bypasses the tunnel path and undermines the entire system. If you have a house design that transitions from cross to tunnel, the need for maintaining ventilation control becomes even more critical until the air becomes stable, even hotter, and consistent through day and night.
And now wind chill is your best friend. The same airspeed that was costing you feed in May is what keeps your birds alive in July.
This is the wind chill paradox, and getting it wrong in either direction has real consequences for your flock and your bottom line.
Where Cool Cells Fit In
Evaporative cooling through cool cells only enters the picture during hot weather ventilation. But running cool cells correctly is more nuanced than most producers expect.
Controllers like Prism’s Command III manage a soak and dry cycle rather than running the water pump continuously. The pads run for a set period, then partially dry before being re-wetted. This matters because fully wet pads evaporate more effectively than constantly saturated ones, and properly spaced cycles reduce the mineral and scale buildup that shortens pad life over a season. Waterlogged pads also increase static pressure at the tunnel inlets, which reduces the airflow you’re depending on.
Research confirms that very short pump cycles — around 10 minutes — produce minimal temperature change and minimal pad drying. The timing and spacing of those cycles is where the real efficiency comes from.
Humidity is the other variable most producers underestimate. When outside relative humidity exceeds roughly 75 to 80 percent, evaporative cooling provides almost no benefit and can actually increase the felt heat index by adding moisture to air that’s already saturated. Controllers with humidity sensing capability can suppress cool cell operation during high humidity periods automatically, rather than running them on a schedule regardless of conditions. That protects your birds and avoids wasting water. (The Command III supports this capability — though whether it’s active in your setup depends on how your system was configured at installation. More on that below.)
The Controller Is the Difference
None of this works the way it should without a controller that understands what mode it’s in and why. The Command III manages fan staging, inlet position, curtain control, and cool cell operation in real time based on temperature, static pressure, and relative humidity readings. It stages fans progressively as temperatures rise, managing airspeed at bird level to avoid the wind chill problem during transitional ventilation while building toward full tunnel capacity as conditions demand.
The difference between a good summer and a hard one often isn’t the equipment. It’s whether the brain running that equipment is making the right call at the right time.
What’s Your Command III Actually Doing?
The Command III is a highly configurable platform. Features like humidity sensing, advanced cool cell logic, and multi-stage pad control are available — but they have to be set up to be active. If your system was installed a few years ago, or configured by someone who wasn’t prioritizing summer performance, you may have capability sitting dormant right when you need it most — or inadvertently had a setting changed throughout the yearly weather changes going unnoticed.Before the heat hits, find out what your Command III is actually capable of. Contact the Prism team for a configuration review and make sure your system is ready before the summer puts it to the test.