Benchracer,
You've come to the right place. Benefit from all of the GJ users before you construct.
Simple answer is use natural gas if available. Assuming your in Chicago, the electric rates are about $0.12-$0.14 per Kilowatt hour. Your 24X24 building will need about 45K BTU to heat just the lower portion. Assuming you insulate perfectly, you would need at least 6KW of Electric to heat. $0.14/KW hrX6KW=$0.90 or almost a $1.00 per hour to run. At 8 hours per day over a month is over $200 per month.
Gas calc's 1 cubic foot of gas is 1000 BTU of heat. I used 1700 cubic feet to heat my whole house for a month and it ran $27. Safe to say that currently gas is cheapest and electric is most expensive. It is proabably true that electric will be cheapest to install from equipment and labor stand point.
Trade offs:
1. Electric: most expensive to run, heats shop quicker, least expensive equipment ($500-$600)
2. Forced air, low-moderate expense to run, takes a little longer to heat shop (come up to temp), equipment not that expensive ($800-$1000) includes gas line)
3. Concrete floor radiant low-moderate to run, takes longest to heat shop if coming from a cold start, equipment is most expensive ($2,000-includes heater, pump, manifolds, and 4 rolls of 1/2 inch pex and foam board insulation), and is most comfortable heat. It can be argued that if you keep it up to temp, it might in fact be the lowest.
The hanging forced air unit like a Hot Dawg will do well, but since you're starting from scratch, consider the concrete floor radiant heating solution. The effect and comfort are like no other.
The single most important item to do regardless of which method you choose is insulate well! Not just the walls/ceiling but under the concrete floor and inside perimeter of the foundation. Owens Corning Foamular #250 should be used the (25 PSI rated 2 inch thick Foam inslulation), not #150 (the 15 PSI version) normally offered at Lowes/Home Depot/Menards/Etc. IMHO, the weight of the concrete and/or loads will crush the Foamular 150 (15 PSI) Foam boards into something useless.
Owens Corning page:
http://commercial.owenscorning.com/products/foam/foamular-250/
And don't be fooled by the air bubble silver rolls. There are many documented cases of fraud with that type of insulation.
If you go with the concrete floor radiant; My suggested solution:
TAKAGI- Jr tankless water heater, circulator pump, four loop PEX manifolds. The Jr model has four heat settings and lowest setting should produce the right amount of BTU's to keep the cycle water solution at 90-100 degrees. use the right oxygen barriar rated PEX tubing rated for Radiant heat applications. 1/2 inch PEX will permit up to 300 foot long loops. Loops should not vary be more than 10 percent differance in length. (300 to 270 feet),loop layout should minimize the number of times you cross and expansion joint, mount heat hardware where nothing will block it and the pex wil enter/exit easily. Suggested source:
www.PEXsupply.com
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and WATER lines in ! ! ! Be VERY SURE to check Zoning ! ! ! ! ! !
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