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Shop smarts

Todd Intermill heats, cools and dehumidifies his 36-by-56-foot shop for $650 per year with an air-source heat pump and an electric furnace. The air-source heat pump moves heat from outside to inside the shop, and vice versa, to maintain the desired temperature. The electric furnace works as a backup in the winter. Its blower distributes the heat pump’s air throughout the shop.

The air-source heat pump is better than in-floor heat, says Intermill, Colman, S.D.

It’s more efficient than a combustion furnace, because nothing is burned to generate heat. Installation is simpler than in-floor heat. There are no valves or pipes to maintain as with in-floor heat. There are no worries about digging up the floor to repair a break in a line as with in-floor heat.

The heat pump works faster than in-floor heat. While it may take an in-floor heat system two days to raise or lower a shop’s air temperature 20 degrees, the heat pump with its forced-air system will do it in less than two hours in his shop, Intermill says.

An air-source heat pump consists of a compressor and two copper tubing coils, one coil indoors and one outdoors. The coils are surrounded by aluminum fins to facilitate the transfer of heat.

In the heating mode, liquid refrigerant in the outside coil extracts heat from the air and evaporates into a gas. The indoor coil releases heat from the refrigerant as it condenses back into a liquid. A reversing valve can change the direction of the refrigerant flow for cooling.

The system needs a little help on the coldest days of the winter, Intermill says. That’s why he has a backup electric furnace. The blower system also distributes the warm air generated by the heat pump.

Intermill insulated the wood-frame shop well. The 8-inch sidewalls have M\zn-inch thick OSB (oriented strand board) sheets on the inside and outside. The outside wall is clad in steel. The inside walls are covered with a high-quality gloss paint. The walls have R26 fiberglass insulation. There’s 18 to 20 inches of fiberglass insulation in the vaulted ceiling, giving it an R rating of 60-plus. The 16-by-24-foot hydraulic door is insulated to R20. Two-inch-thick expanded polystyrene boards insulate the concrete slab and foundation.

Solar energy

Sunlight from several 3-by-3-foot and 4-by-4-foot south-facing windows helps heat the shop in the winter.

Two 57-inch shop fans mounted on the ceiling recirculate warm air that collects in the peak of the vaulted ceiling. The air can be as much as 8 degrees F warmer near the ceiling than it is near the floor, Intermill says.

Simple – but handy – shop ideas

There are lots of simple, handy ideas in Todd Intermill’s shop. For example, his tool chests are different colors. Each color indicates a different type of tool. Black is for metric tools; blue, air tools; red, standard wrenches; and green, specialty tools. When someone is trying to find a particular tool, Intermill doesn’t have to describe where the chest is located. If someone wants a wrench, he just says, “Look in the red one.”

More plans for next time

Todd Intermill says there are a number of things he could do differently to make the shop even more energy efficient. If he were building another shop, he:

• wouldn’t insulate the slab. The ground beneath the slab stays between 45 and 50 degrees F even through the winter — if the frost stays out of the soil under the floor, Intermill says. He would insulate the foundation to a depth of 4 feet or more to keep the frost out and just put a vapor barrier under the slab. “If I hadn’t insulated the floor, I could have used more natural heat coming up under the building,” he says.

• would build 10-inch rather than 8-inch-wide walls so he could put in more insulation.

• would reduce the number and size of the ceiling fans. He has two 57-inch industrial fans in the shop ceiling now, but figures he needs only one 52-inch residential fan, or one fan for every 2,000 square feet. The bigger fans move too much air, even at low-speed settings, and the floor feels drafty when they run.

• would mount a sensor on the outside of the shop to turn the security light inside the shop on at dusk and off at dawn. The sensor costs about $50 and would have been well worth the investment, Intermill says.

• would install windows at the top of the south-facing wall so that in the winter sunlight would reach all the way to the opposite side of the shop.

LOSER BOARD: There’s nothing wrong with the wrenches hung on the loser board. They are the ones that can be used outside the shop, where they are likely to be lost — hence the “loser” label. But no other tools can be removed from the shop.

Todd Intermill writes on the erasable white board that covers one wall in the shop office.

MUSCLE: A 6,000-pound over-head crane made by Intermill can reach across the shop to move heavy objects.

Todd Intermill built an energy-efficient and highly functional shop.

PAPER PLACE: Delivery drivers and employees leave receipts, scale tickets and other paperwork in the mailbox by the shop door.

This article published in the November, 2010 edition of DAKOTA FARMER.

All rights reserved. Copyright Farm Progress Cos. 2010.