How big will your energy bill be this winter?

Just returned from the local barbershop. While there, visited with a local heating contractor about energy costs. He had just booked his propane for this winter at $2.30/gal, up considerably from last summer’s booking.


I’ve also heard of grain farmers trying to decide if they should book diesel fuel for their fall harvest operations this summer. Some are advising to do the bookings now in anticipation of further price increases, while others are suggesting the ‘bubble’ may burst on energy futures and fuel will be cheaper this fall. As this suggests, ‘cheap’ is in the eyes of the beholder.


The cost of energy for swine production units will be up considerably this next winter regardless of which scenario you want to plan for. As a point of reference, fuel and oil expense for the past 4 years for cooperators in the Minnesota Farm Business Association ( have averaged $1.43/pig for wean-finish, $0.71/pig for feeder pig finishing and $0.49/pig for breed to wean. Note that this fuel and oil includes not only propane, but also any fuel use by tractors, generators, pickups, etc. that is charged to the hog enterprise.


Utility expense (generally electricity and telephone) were $1.04/pig for wean-finish, $0.62 for feeder pig finishing and $1.03/pig for breed to wean.


These expenses seem minor compared to the explosion in feed ingredient prices, but a 25-40% increase in these costs is still a shock to many. I’ve been getting a number of calls from clients to do ‘energy audits’ at their production sites. In general, during these ‘audits’ I focus on issues associated with the ventilation system, including set points, bandwidths, furnace sizing, inlet adjustment, etc.


One question commonly asked regards insulation. In southern Minnesota and northern Iowa, many producers have asked about the value of a ‘warm-wall’ wean-finish versus a ‘cold-wall’ facility as it relates to energy savings. A ‘warm-wall’ facility is usually a tunnel ventilated unit that does not use emergency drop-curtains on the side walls. Instead, the walls are fully insulated, often to a R-19 value. This is in contrast to ‘cold-wall’ facilities that have un-insulated stem walls with a 3’ emergency drop curtain, which translates into an effective R-3 value for the side wall.


When I model heat production by a 25 pound pig in these units and add in heat loss from the building shell and heat loss from the ventilation system, the most striking item is the impact of incorrect ventilation management on heat loss. The model I use predicts the balance point temperature of a facility, that is, the temperature of the incoming air that is at balance with the heat loss from the building shell and ventilation system.


A typical 1200 head wean-finish facility in the upper Midwest has 2 24” variable speed pit fans as the stage 1 ventilation. If we assume that each 24” fan has a rated capacity of 6000 cfm, 2 fans operating at full speed equates to 12,000 cfm or 10 cfm/pig. The recommended ventilation rate for moisture control for 25 pound pigs is 2 cfm/pig. Even if the stage 1 ventilation controller can reduce fan output to 50% (notice I didn’t say slow the fans to 50% speed or 50% setting on the controller), this is still 5 cfm per pig with 2 fans operating and the room housing 1200 pigs.


At this setting, the estimated balance point is 43 F for the cold-wall barn and 45 F for the warm wall barn – not much difference, suggesting that a large amount of the heat loss is associated with the ventilation system. If one of the 24” fans is turned off so the ventilation system provides 2.5 cfm/pig, the balance temperature for the cold-wall facility drops to 22 F while it drops to 10 F for the warm-wall facility. Now there is clear value to the insulated ‘warm-wall’.


The above example demonstrates the importance of thoroughly understanding your ventilation controller and matching your ventilation system to the number and size of pigs in the facility. If you don’t get the ventilation right this fall, plan on buying a lot of $2.30/gal propane.

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