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When the Nelsons of Belmond, Iowa, built their shop in 2008, a top consideration was how they would keep it warm in colder months. Brothers David, Dennis, and Neal turned to Chris McMurray for guidance on how to heat their 80×80-foot building.
“We laid out the heating, and I broke it down as to what their best options were for a shop that large,” says McMurray, who owns McEzs, a plumbing, heating, and refrigeration business in Meservey, Iowa.
McMurray says there are basically three types of systems to choose from.
1. Radiant Hydronic. This system uses water to carry heat from a boiler unit through a series of pipes placed under a floor or embedded in a concrete floor. “One of the biggest advantages of this system is that the entire floor is warm,” says McMurray. Boilers can be placed just about anywhere. That's because the flame is enclosed and the system is only heated to around 130°F.
2. Radiant Tube (Infrared). “Radiant tube heat, or infrared heat, is a heater that hangs from the ceiling with the reflectors,” says McMurray. “It's the one that, as you walk into a building, you get blasted with heat. It heats the object from the top down.”
3. Forced Air. This system doesn't heat objects but rather the air, and basically it uses a flame to heat the air. Most of the time this system hangs from the ceiling away from objects that can overheat. Because heat rises and heat is produced at the top of the room, this system is relatively inefficient.
Of the three, McMurray recommended in-floor heat for the Nelsons' shop. “My initial thought was that they needed to do this radiantly in the mass,” he says. “By going with radiant heat through the concrete, you can heat an area the size of the Nelsons' shop very cost effectively.”
The brothers also did their homework. “We talked with people who installed in-floor heat, and they said they really liked it,” says David Nelson.
“Right now I'm putting 95°F. water into that floor, and it's maintaining +60°F. in their shop,” says McMurray.
What's the feature the brothers like most? “The best part is that the floor is warm so our feet are always warm,” says David Nelson. “We can open the large door on a cold day to bring in a piece of equipment, shut it, and within five to 10 minutes, the shop is back to 60°F.”
How to decide
Ultimately, the size and type of heating system you choose will depend on the size of the shop, how often the shop is used, and how often large doors will be opened and closed.
According to Kenneth Hellevang, North Dakota State University, the heating system for a shop should provide about 50 Btu per square foot per hour depending on desired shop temperature and building insulation level.
“A 40×50-foot shop would require about a 100,000 Btu-per-hour heating system,” Hellevang says. “If a floor heating and forced air system is used, the heating requirement may be divided between the two.”
Where appropriate, Hellevang and McMurray recommend using zone heating. “If there is any variation in what you need for heat in areas segregated from the rest of the shop, it's worth thinking about zone heating,” says Hellevang.
“The Nelsons' shop is split into three zones,” notes McMurray. “The office is one, and the shop is divided into two.”
He says zones are set up with pumps rather than valves. “I don't zone with zone valves because they cost more than pumps,” McMurray says. “With pumps, I can isolate areas so I can shut them off on either side. I also would rather install four smaller pumps rather than one gigantic pump to do the work. By doing it that way, if one pump goes out, you still have the others to fall back on.”
Besides the type of system, you also must decide on the most economical fuel source.
“There are a number of options available,” says Hellevang. “The key is to analyze all of the costs involved with each and make your decision based on that.”
For example, he says wood is a viable option, but there are hidden costs to add into the equation like labor; you can't simply look at the cost of the wood.
Other possibilities include corn, which the Nelsons used initially.
“Corn boilers are great if there is somebody to maintain them daily,” notes McMurray. “When it burns, corn is so caustic that it just ate that machine up from the inside out because it wasn't maintained. The corn boiler failed so many times the Nelsons finally decided to get rid of it, and I put in a new boiler that uses liquid propane.”
Hellevang says no matter which way you go, it's important to look at insulation. “With fuel prices the way they are today, you need to make sure the shop is well insulated,” he says. “Know what the recommendations in your area are for the R-value of a farm shop.”
Should you go geo?
While McMurray would have liked to have seen the Nelsons go with geothermal heat (which is a type of radiant hydronic heat) from the start, cost was a deciding factor.
“The boiler was around $7,000,” says David Nelson. “All of the underground piping was another $7,000 or so.”
McMurray says, “The tubing will cost the same no matter what drives it, but the geothermal equipment is probably double a boiler in cost. The initial cost for geothermal is going to be twice as much because you have a loop field and then your equipment to drive it.”
Depending on size, location, and terrain, the underground loops are the most expensive part of this system. “But once you hit your payback, it's starting to pay you to use it. Whereas with a gas-fired boiler or corn boiler, you'll always have that cost of the fuel,” says McMurray.
That's not to say the brothers have completely ruled it out. “I have it all spec'd out to move from the boiler to geothermal,” says McMurray. “The dollar willing, we will pour the tubes this coming fall. They will then use the boiler as a backup or for emergency-type heat.”
The geothermal system has some added incentives. “Some electric companies will give you a 5¢-per-kilowatt rate to run geothermal equipment, and USDA will give you a 20% grant on farm buildings,” says McMurray. “There's also a tax credit of around 30%. It might be worth taking a look at, especially if your shop qualifies for any of these incentives.”
Regardless of the system you choose, McMurray has one final piece of advice. “Even if you don't have the money to put a heating system in your shop initially, bury the tubes in the concrete anyway because you can't go back,” he notes.