The Bigger, the Better?
By Shawn Conley
Factors to consider when deciding on barn size
By Shawn Conley
For many farmers, building a new barn is a once in a lifetime experience. Few farmers will have the opportunity to build more than one new barn, let alone an entirely new farm. There is only get one chance to get it right — and it’s crucial that the latest technology and research is used to build the ideal barn. In this industry, getting the barn and equipment right can make a bigger difference, possibly, than in any other industry (especially in terms of performance of the product and the profitability of the farm). For this reason, it is extremely important to do the necessary homework into the latest innovations. Poultry barn dimensions are a great place to start.
Is Bigger Really Better?
In general, the bigger a barn is, the lower the production the cost is per square foot, and therefore, the cost per bird. In Canada, tunnel ventilation has not historically been the ventilation of choice, but as summers here have become increasingly hot, and bird sizes have ramped up, the U.S. style tunnel building has begun to enter the Canadian system. We need to look at the lowest cost, highest return way to construct these barns. Building fewer barns with more square feet has helped producers come out ahead. In the U.S. and other countries, typical sizes have been around 40’ x 500’.
More recently, the pressure of producing more or bigger birds has led to the trend of adding width to barns because a small increase in width adds a lot of space without a lot more cost. Widths over 60’ have become common in these new barns. Some of the considerations we need to factor in when doing this are the structural demands, management style, housing the equipment needed — and perhaps most importantly — how the building will be heated and ventilated.
Everything about the structure should be designed by an engineer with experience in the region in which you are building. Most people know that the trusses need to be engineered due to snow load requirements or wind, but there are many other “pillars” in the design of a building, from the soil under the building, to the concrete, to the bracing and anchoring of the trusses. All of them could be a source for structural failure. With a building of widths over 60’, everything matters, even the quality of the materials.
Management and Equipment
It may be that it is more efficient to manage less buildings, so from this standpoint, it makes sense to go bigger. Maintenance inside and outside buildings is reduced, and daily tasks like picking up mortalities, adjusting equipment, tweaking controllers need to be done less frequently.
When it comes to setting up equipment configurations, feed and water affect the ideal dimensions of the barn. If most feeding equipment companies recommend approximately 55-75 birds per pan to maximize efficiency and provide enough feeding space, based on this, in a 500’ barn with a standard density of birds, we would need 18-22 feet of width per line. That means we need to go 36-44’, or 54-66’ wide, otherwise we are wasting feed space and money by installing too many lines, or we are cutting feed space and sacrificing performance, which will cost more over the long run.
The way the heaters fit into the system can get complicated. Making sure you can get the right number of BTUs into the barn while at the same time covering the floor space adequately is a tricky balance. When working with a 40’ wide barn with high ceilings, a standard tube heater can cover well, but with a low ceiling, the same building may require a newer style short U-tube style heater with a wide heat footprint. In a 60’ wide building, the short U-tubes can still work if spaced closely, but two rows of regular tubes will definitely be needed for 66+ foot wide barns.
A 60’ wide barn is not as simple to ventilate as a standard 40’ wide, although it can work better. It is mandatory to minimum ventilate with inlets on both sides, and utilize ceiling inlets if possible. Instead of air needing to travel nearly all the way across the 40’ barn, the air only needs make it about 25’ to get close to the center. This is assuming that most barns are still being cross ventilated — it is still easier to get the air travel if ventilating a two sided system in a 40’ wide building. It is important to make sure static pressure is 0.1-0.12 to get the proper air velocity and travel.
When setting up tunnel ventilation systems in wider buildings, note that the best ratio of length to width for proper airflow is 11-12:1. If you want to build a wide building to minimize cost per square foot, a 60’ x 500’ will not run as efficiently as a 50’ x 600’. So, even though a 40’ wide may cost as much as 15 per cent less per square foot to construct, it may cost more over time due to inefficiency.
The message here is that there is no absolute solution to building dimensions, although a 54’ x 600’ is the closest we can come to a standard for a tunnel barn. It gives the right ratio of width to length for airflow in tunnel and minimum ventilation, and also allows enough space for feeders and drinkers. In addition, a single row of newer style short U-tube heaters down the center would work well.
With all that said, every situation requires a thorough analysis to figure out the best configuration for your farm, birds, and future business plan. Do your research, and utilize your industry experts.