Poultry barn air quality trends

These days, whether producers are retrofitting a barn or building a new one, they will face the same ventilation challenge – they must ensure capacity is adequate to safeguard bird comfort year-round while also minimizing energy costs. That said, here are some of the ways Canadian experts suggest accomplishing this feat. 

Increasing knowledge
Producers are becoming more knowledgeable about how the different aspects of barn ventilation interact. Experts would like to see that trend continue. “There are some producers who really understand how everything should work together,” explains Kevin Weeden, president of Weeden Environments, a barn environment specialist company in Ontario. “But many need to increase their understanding so that they can make educated decisions.

“In Canada, barn fans, inlets, cool cells, heating and more must all be set up to ensure birds are kept comfortable when the external weather is extremely cold or hot. The importance of minimum ventilation in the winter is often discounted when considering barn ventilation design. In the first week of February in Canada, every producer needs to make sure the barn is capable of providing adequate air exchange.”

Ensuring adequate capacity
Indeed, in providing barn ventilation design across Ontario and parts of the U.S., Weeden and his team talk to many producers who have barns that lack adequate ventilation. For example, they often speak to farmers who have had tunnel barns built without anywhere near the fan capacity needed to produce the wind speeds for tunnel ventilation to function properly during times of heat stress.

Bill Van Heyst, a professor of engineering at the University of Guelph in Ontario who studies barn ventilation, agrees. “Simply putting on larger or more fans in a tunnel-ventilated system may not do the trick,” he says. 

Van Heyst and one of his graduate students have been working on modelling air-flow in a poultry barn using computational fluid dynamics under minimum and maximum ventilation scenarios. He believes modelling will provide a better understanding of the indoor barn environment, which in turn will lead to enhanced spatial analysis of wind velocity, enhanced prediction of ammonia and particulate matter generation and other factors. 

Ian Rubinoff, a veterinarian and director of global technical services at Hy-Line International, adds that when converting flat deck houses to aviary house layer barns, producers must upgrade their ventilation. Aviaries require much more ventilation because of physical barriers and the greater number of birds they house, he explains.

“I would actually argue that in an aviary or a free-run layer barn, two ventilation systems are best – a minimum ventilation side wall system for winter and a tunnel ventilation system for summer,” Rubinoff says. “Producers can switch back and forth and always have the ventilation needed for proper temperature control and to keep litter dry to ensure good air quality and welfare. Many smaller cage-free houses (with less than 100,000 birds) being built in the Midwest U.S. at this time are putting in dual ventilation systems.” 

Another common ventilation issue that producers sometimes don’t understand is that adding a cool cell is going to require 20 per cent more ventilation power, explains Bryce Bramhill, operations manager at Weeden. Because the cool cell increases air pressure, this acts to lower windspeed. Thus, more fan power is required to achieve the same speed. And whereas five years ago cool cells were unique in Canada – at least in Ontario – Bramhill says they are very common now with the hot summer weather that’s becoming the norm.

“A cool cell is part of every quote now,” he observes. “We always recommend that every producer sits down with an experienced person who can explain ventilation so they can make educated decisions and select the best design. Producers need to understand whether or not they actually need a cool cell, cross flow versus tunnel systems, what continuous baffle or modular sidewall inlets provide, what attic inlets can do, etc. They need to understand their particular barn and also the weather that’s typical in their geographic area as well.” 

Larger and more efficient fans
In terms of fan performance, Weeden advises producers to compare the results of the annual tests at BESS Lab at the University of Illinois, a well-known and trusted fan analysis facility. 

Due to their high performance, lower maintenance requirements and their now-lower costs, direct-drive, variable-speed fans are becoming much more common. They generally produce higher air volumes per minute per watt than similar single-speed, belt-driven fans. 

“The use of more of these fans is great for low-ventilation scenarios like winter when you want to have more incremental increases in your ventilation,” Van Heyst explains. “This helps prevent excessive heat loss due to over-ventilation with simple on/off type fans.”

Overall, many experts consider large, direct-drive variable-speed fans a new, exciting development that can save producers a ton of money. For example, the Weeden team says that a producer running two 54-inch VAL-CO V-Fans running at 50 per cent speed can move 13,400 CFM (cubic feet per minute) at 0.05 static pressure while achieving 53.8 CFM/watt, which is more than a 300 per cent increase in efficiency.

And, as poultry barn size has increased, companies are marketing larger and more powerful fans to ensure efficient air movement. In 2020, the Weeden team installed exhaust fans as large as 72 inches. They recommend only using smaller fans if absolutely needed and to, conversely, use as many larger fans as possible. That’s because, variable speed or not, larger fans are more efficient. 

Preventing baffle and freezing
In terms of incoming air, Bramhill says most producers are still battling with both continuous baffle and modular side wall inlets freezing up during the coldest parts of winter. To avoid this situation, which can negatively affect both bird health and power consumption, he recommends one of two solutions. 

The first is to use a side wall inlet designed for good performance in frigid temperatures. “The other is to use attic inlets where tempered air from the attic is introduced to mix with the warmest air in the barn having risen to the ceiling, and then it’s gently mixing that air over heaters,” Bramhill says. “More and more growers are using attic air, and I don’t think we’ve equipped a barn in the last two years without them.” 

Van Heyst believes any method of preheating air is always good, and that a lot of barns are designed with the incoming air first entering the attic space and then being dropped through the ceilings as a way of heating the air up a bit. “Pre-heating the incoming air does require specialized equipment, usually in the form of an air-to-air heat exchanger,” he adds. “These range in size to units that are mounted single fans to larger centralized heat exchangers.

“We have measured ammonia and particulate matter in one broiler barn with a centralized heat exchanger and found that the litter was drier (and hence had more particulate generation) as a result of low moisture content of the cold outside air and the higher ventilation rate that was used (venting out the moist barn air).”

Technology evolution
In the next five to 10 years, Weeden expects that remote control of the barn environment will continue to improve. “Already, the communication between the barn systems and the producer is improving,” he says. “You used to get an alarm with very little information provided. And now with controllers linked to your smartphone, you have instant and detailed information pertaining to which specific heater is producing too much heat or which individual fan motor has died. 

“I also think that artificial intelligence will be coming in the future where controllers will begin to learn and anticipate user preferences to automatically make improvements in environmental parameters. Sensors are also evolving and I believe ammonia level, for example, will be another parameter that will soon be commonplace in any ventilation set up. And there will clearly be much more use of wireless systems.” 

As the genetics of broilers, layers and turkeys evolve to enable faster growth and climate change effects worsen, Weeden says ventilation systems will continue to adapt. He says that even with modern technologies, producers still need to carefully plan what they select and how it will interact with existing equipment. “Overall, whether it’s cold stress or heat stress, it’s about the birds being comfortable, so educate yourself before you make your decisions to maximize flock health and avoid costly retrofits.”  

Key ventilation trends for 2021
Increasing Knowledge Level: Producer understanding of how barn ventilation works and the merits of various options is growing, enabling them to make more educated decisions.

Ensuring Adequate Capacity: Across the industry, under-ventilated barns are becoming scarcer and well-ventilated barns are becoming more widespread. 

More Efficient Fans: Producers are adopting larger, direct-drive, variable speed fans because they provide the most efficiency.

Avoidance of Inlet Freezing: While many producers still struggle with this problem, more of them are implementing strategies and tools that solve the issue permanently.

Better Remote Monitoring: Barn ventilation and environment sensors are becoming more specific, allowing easier and more effective remote management.