Talk to a farmer about building a farm shop, and you can pretty well tell what part of the country they’re from by how interested they are in insulation. Southern farmers are often indifferent to insulation, though the improved work environment provided by air-conditioned shops has made insulation increasingly popular in southern shops. Northern farmers, however, take insulation seriously when building a shop and need to be conversant about climate zones, R-factors, air/vapor barriers and other variables that dramatically influence the cost and efficiency of heating or cooling their shop.
Here are pro tips to consider when insulating a shop:
1. Optimal insulation of a building starts with its foundation. Shops with in-floor heating require sheet-foam beneath the entire concrete slab to act as a thermal break that prevents heat transfer between the slab and ground. Buildings without in-floor heat can benefit from foam sheets installed vertically around the perimeter of the slab to a depth of a couple feet to reduce heat loss into the surrounding soil. “Insulating the perimeter of a shop floor that doesn’t use floor-heat isn’t absolutely necessary, but is better than not insulating it,” says Nick Horstman, Morton buildings representative in central Iowa. “If you want to reduce heat loss over the building’s lifespan, laying insulation along the foundation is probably cost effective.”
2. R-value is a measure of how well a barrier such as a layer of insulation, a window pane or wall components resist the conductive flow of heat. Steel siding has an R-value of 0.61, ½" plywood has an R-value of 0.63, and a single-layer glass window is rated at 0.91. Higher insulation values come with fiberglass batts providing R-3 per inch of thickness, closed cell foam offering R-7 per inch, and blown cellulose yielding around R-3.85 per inch.
3. Air barriers and vapor barriers are adjuncts to some types of insulation. Air barriers control air infiltration and reduce drafts. Vapor barriers control the movement of water vapor to prevent condensation on or in walls and windows.
4. Fiberglass insulation provides economical insulation but for optimum results requires attention to detail during installation. “Fiberglass is not an air barrier,” says Dan Frisch, with Cullen Insulation, Fargo, N.D. “If you’re using fiberglass, the exterior sheeting needs to be air-sealed in some way to stop drafts and air infiltration.”
5. Fiberglass insulation will absorb and hold moisture. Open cell foam absorbs and holds moisture. Closed cell foam is water resistant.
6. Open-cell spray foam can serve as an air barrier if applied in thicknesses greater than 3 3/4”. While open-cell foam tends to be a lower priced spray foam per inch of applied thickness, it requires thicker applications than closed-cell spray foam to achieve comparable R-values.
7. Closed-cell spray foam is a heavier, denser product that provides an R-7 value per inch of depth. “A 3" layer of closed-cell (foam) in a wall provides R-21, plus it’s a vapor barrier and air barrier,” Horstman says. “It really seals up a building. Plus, depending on the thickness after it cures, it can strengthen the exterior building envelope to some degree.”
8. Closed-cell spray foam sprayed on the inside of exterior sheet metal might make replacing damaged sheets difficult, nearly gluing them together. “If the bottom of a roof has been spray-foamed, for example, and gets significant hail damage,” Horstman says, “we’re finding it’s easier and more cost effective to just install new rows of purlins on top of the damaged roof and lay new sheet metal right over the old roof.”
9. Hybrid insulation packages combine spray foam, fiberglass batting and blown-in attic insulation for optimal economy and performance. “You can foam the walls with an inch or so of foam, fill the rest of the wall cavity with fiberglass batts, then blow insulation into the attic,” says Scott Bickett, Illinois Valley Insulation, Princeton, Ill. “The foam seals it, and the fiberglass does a good job insulating at an economical cost.”
10. Spraying an entire building with closed-cell foam is a one-and-done process, but it could also increase your heating bills when compared to a multistep insulation process. “If you just coat the inside of all the walls and the bottom of the roof with closed-cell foam, that means you’re heating the attic,” Bickett says. “In a big building, that’s a lot of space. We recommend insulating the walls, installing a ceiling on the bottom of the trusses, then blowing in fiberglass to get an R-30 value to keep from heating the attic. Compared to the cost of spray-foaming the extra square footage of the sloped bottom of the roof and the gable ends to R-21, you could put up a ceiling, spray just the walls, blow R-30 fiberglass above the ceiling rafters and avoid heating the attic, all for about the same money as spray-foaming everything.”
11. Spray foam could create warranty issues. “Some building manufacturers don’t want foam sprayed directly on steel siding,” Horstman says. “Especially if it’s lighter gauge sheet metal. As spray foam cures, it expands slightly, and that can create pressure between wooden framing and steel siding, causing thin siding to bow. Twenty-six gauge or thicker siding should be fine, but there could be issues in siding thinner than 29-gauge. To avoid this issue, we prep our building by putting housewrap or plywood inside the sheet metal for the foam to be sprayed on, to act as a break between the foam and exterior steel.”
12. Fiberglass insulation is fire retardant and could find favor with insurance agents for that reason. Because spray foams are not fire-retardant, most insurance companies require at least the lower 8' of foamed walls in farm shops be covered with sheet metal or plywood, or coated with a fire-retardant mastic/paint.
13. Any type of insulation, properly installed, will help keep a farm shop warm/cool. “Fiberglass is economical and does a great job if all surfaces are sealed against wind and air infiltration,” Frisch says. “Sprayed open-cell foam provides an air seal and has good R-value if applied thick enough. Closed-cell spray foam creates an air and vapor seal, and offers good R-value per inch of thickness. It’s up to the farmer to work with his building contractor and insulation installer to figure out which insulating system best fits their building, their climate zone and their budget.”
14. Air-conditioned farm shops are gaining popularity as owners learn how much more productive they are on hot, humid days inside cooled shops. “Heating and air conditioning are pretty much the same when it comes to insulation,” Frisch says. “The only difference is where condensation develops if there’s not a vapor barrier.”
15. Money will buy R-value when it comes to your shop’s windows. “A double-pane window is more expensive,” Frisch explains, “but you won’t see as much condensation on the warm side of that window. The more separation you can get between warm and cold, the more heat you’ll hold inside the building.”
Your Next Read From Dan Anderson’s Shop Building Series:
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Farm Shop Concrete: One Chance To Do It Right
