Calf barn ventilation options when building new

By Harold K. House, M.Sc., P.Eng.
Agricultural Engineer, DairyLogix

Choosing a ventilation system for a new calf facility will depend on several factors:

1. Natural versus fan ventilation
2. Individual versus group pens
3. Cold versus modified housing
4. Operator preference
5. Operating cost

The first major factor is: “Will my ventilation system use natural ventilation or fan powered ventilation?” Natural ventilation works best when a calf barn is a standalone entity that can be oriented to make best use of wind direction, or a separate room that projects from the barn and can make use of natural air flow. If this is not possible, the best option is a fan powered ventilation system.

Natural ventilation uses large adjustable sidewall openings to deliver natural air flow through the barn or room for summer ventilation and chimneys are used in the winter to provide for air exchange and exhaust. In calf barns, it is best to automate the curtains to adjust for changing conditions.

Fan ventilated barns use adjustable air inlets mounted in the ceiling to distribute fresh air into the barn or room. Fans are used to exhaust air from the room. The fan capacity is sized to meet the ventilation needs of the calves and the number of air exchanges needed for proper ventilation.

Air inlets are used primarily for late spring, summer, and early fall ventilation. Systems must be designed so that fresh outside air does not pick-up attic heat before it enters the room. The location of the air inlets dictate which system works best to avoid picking up attic heat. If one or more rows of ceiling inlets are used in the design, it is best to use the entire attic space as the air plenum. In this design, air enters the attic through soffit inlets and is then pulled through the ceiling inlets by the exhaust fans. The attic must have insulation under the roof steel so that the air does not absorb heat through the roof. The air exchange through the attic should be one air exchange every 45 seconds or less, to avoid absorbing attic heat.

If the air inlets are in the centre of the room and the truss is a standard ‘W’ design, an insulated duct can be constructed using the truss webs for support to deliver air to the ceiling inlets. If the inlets are located along the outside wall, the system can be designed so that air can enter through the soffit and directly enter the ceiling inlets without picking up attic heat.

The minimum ventilation requirement for calves from birth to weaning is based on 17 m³/h (10 cfm) or four air changes per hour, whichever is greater. It is difficult to establish a good ventilation pattern to distribute this small amount of air evenly with either a natural ventilation or fan ventilation system alone. A positive pressure ventilation tube system (PPVT system) is the best method to supply the small amount of air required for minimum winter ventilation and distribute it evenly throughout a calf room or barn. The air speed at calf level should be less than 0.3 m/s (60 fpm) or the calves will notice the air movement as a draft. A PPVT system can be designed to meet these requirements.

A variation of the basic PPVT system is a double walled tube design that allows the system to be used for both winter and summer ventilation. When the tube is in one position the fan inflates the winter tube with appropriate sized holes, and then by rotating the tube the fan inflates the other tube with summer sized holes. With this design the system can supply the winter ventilation rates and a portion of the summer ventilation rates.

Calves require extra air and at higher speeds in hot weather for cooling. They should have at least 170 m³/h (100 cfm) per calf or 40 air changes per hour. Air speeds of 1.3 m/s (250 fpm) are needed for cooling. In naturally ventilated barns, the reliance is on outside wind speed to provide this extra volume of air. Unfortunately, the hottest days are often the days with the least amount of wind. Therefore, in the summer it may be necessary to use panel fans to direct air at higher speeds to the calves. Panel fans work well to provide air at higher speeds in a group pen situation. In a barn or room with individual pens and solid partitions, a PPVT system with tubes designed for summer ventilation can be used to direct air into individual pens. Ventilation in group pens is more forgiving as calves can move to find the most comfortable location.

In a fan ventilated barn with individual pens, the fan capacity and air inlets should be sized and positioned to direct summer air volumes through the calf pens. Summer air tubes can still help to deliver air directly through the pen. Fan ventilation works well in both individual and group pen situations.

A third factor to consider is cold versus modified housing. Supplemental heat should be used in a calf barn to dry out incoming air to improve the fresh air exchange, not to make it more comfortable for the operator. It is best to keep the room temperature below 10^oC and it can be set as low as 4^oC to keep the environment above freezing while still maintaining fresh air exchange. At temperatures below 10^oC it may be necessary to use calf coats to improve insulation and preserve body heat. A cold, naturally ventilated barn without heat will only stay a couple of degrees above the outside temperature.

Finally, ventilation choices often come down to operator preference, whether they would prefer working with natural ventilation using adjustable curtains and chimneys relying on wind speed and direction, or fan ventilation with controlled inlets and more automation. Operating costs associated with each is also a factor. 

There are many other things to consider when designing a calf housing facility beyond the ventilation system. The design needs to consider labour requirements for feeding, bedding and manure management, and health management to name a few. The more time spent in planning a facility will be rewarded when the project is completed.