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Old 10-18-15, 02:50 PM   #4
JRMichler
Apprentice EcoRenovator
 
Join Date: Apr 2012
Location: Phillips, WI
Posts: 103
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I built a heated garage/workshop in 1985. The heat was from two rows of heat lamps in the ceiling. Ten heat lamps at 250 watts each for 2.5 KW. That was enough to maintain 60 degrees in all but the coldest weather.

The floor was pitched 2" back to front, and an additional 1/2" sides to center at the front door. That worked perfectly. I could drive in my car with a full Wisconsin winter load of ice underneath, eat supper, and have the ice all melted off. The melt water drained out under the car, so the floor was dry on both sides and in front.

My current shop was originally built as a garage. I added 2" Styrofoam around the slab. The Styrofoam goes down 24", and out 24". There is no insulation under the slab. The wall studs were doubled to make room for 7" fiberglass batts, plus 2" Styrofoam on the outside. The ceiling was covered with drywall, foamed from above, then fiberglass blown in for a total R-value about 80. The 16' insulated steel door has 1" foil faced polyiso insulation glued to the inside. Heat is from a water to air fan coil unit that I built.

The floor stays warm enough that I have no desire to heat it. It would be even warmer if there was foam underneath it.

The total heat loss is about 10,000 BTUH. I leave the thermostat at 65 degrees. The highest inside temperature during an unusually hot summer was 70 degrees. A well insulated shop does not need air conditioning.

It will need a dehumidifier. A dehumidifier is especially important in an insulated building with minimal internal heat gain. Without it, the entire inside with be a moldy swamp whenever the outside dew point is above the inside temperature.
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