How much insulation do I need to save propane expense?

I’m writing this blog on Tuesday morning just prior to heading out for the Illinois Pork Congress in Peoria where I am on the program tomorrow. Once again a winter storm is passing south of Minnesota and covering the central portions of the corn belt with snow to be followed by cold temperatures.

The governors of Iowa and Minnesota have declared energy emergencies due to the shortage of propane. This morning there was talk on farm radio of a possible change in a pipeline so as to send more propane our way yet this spring.

On top of all of this, the wind and wind driven snow this winter has made for dreadful driving in the open areas of our region. I have had reports of several barn ceiling collapses due to snow drifting into attics. Will winter ever end?

If you had snow in your attic this winter (have you even dared to look in your attic), once spring comes be sure and do a thorough investigation of the roof and ceiling structure. If the insulation became soaked, even once it dries it will be compressed and have a much lower R value. You may need to talk with an insulation expert about how to return the ceiling to a reasonable R value.

What’s a reasonable R value? In most cases R=30 is more than sufficient for swine facilities, even for nurseries and farrowing rooms in Minnesota. The vast majority of the heat loss from a swine production facility is associated with the ventilation system. Wall and ceiling insulation is there to keep the surface temperature high enough to minimize or prevent condensation.

When I model heat flow from a 1200 head swine nursery heated to 84F with minimum ventilation set at 2 cfm/pig, going from R30 to R40 in the ceiling makes almost no difference in the expected use of propane (gal/hr) with newly weaned pigs. Going from R20 to R30 only adds 0.1 gal/hr to the propane usage when the incoming air is -20F.

In grow-finish facilities where the minimum ventilation rates are higher for moisture control, it makes even less economic sense to install ceiling insulation with high R values. For ceilings in grow-finish facilities, R25-R30 is generally more than sufficient given the fact the minimum ventilation rates are often 4.5 to 5 cfm/pig when 55 lb pigs are placed in a facility.

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