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Warming trends

Features, On the Job | October 1, 2013 | By:

Provide a safe, comfortable environment for guests by matching the right heating solution to a tented event.

A proper heating system can extend the tent-event season into cooler months. By understanding the different types of heating methods, their pros and cons, and special considerations, tent rental companies can let clients know that they don’t have to limit tent time solely to the summer months—and all the while provide a safe, comfortable environment for their guests.

Which way to warm?

There are three different methods for heating a tent. One is indirect heat, in which the fan of the unit blows air across a heat exchanger, sending the hot air into the tent from the outside through ductwork. Indirect-fired heaters typically operate on propane but can use heating oil, diesel or natural gas.

The direct-fire method is just as it sounds: air passes directly over an open flame to heat a space. These types of heaters most often rely on propane and are ducted into the tent.

Electric, the third method to heat tents, emits warmth from coils within the unit. Electric heaters run off of diesel generators or tap into utility power located on the site of the event. Tent rental companies also can employ an HVAC system, in which the heating and air conditioning are
tied together.

Each method has its advantages and disadvantages, and the ultimate choice depends on the municipality, along with the type and site of the event. With direct-fired heaters, some of the products of combustion can end up inside the tent since there is no heat exchanger as there is with indirect heating. “Indirect fired heaters are 99.9 percent always the heating of choice for tents [over direct fire] since the flame is enclosed in a separate heat exchanger,” says Buddy Phillips, a regional manager for Atlas Sales and Rentals Inc., which has nationwide locations. “Thus flame is less likely to combust foreign material, which is much safer.”

Propane is the most common fuel used for both indirect and direct heaters. It is odorless, not to mention the most affordable and efficient energy source (it burns at about 99.5 percent efficiency). “The bad news is that some municipalities will not allow you to use propane,” says Spencer Etzel, president of the SEC Group in Wilsonville, Ore. “There are just certain fire marshals who believe that propane is a giant fire hazard, and they won’t let you have it no matter what.”

The biggest fear about propane, Etzel says, is that someone will knock a tank over, break one of the supply lines, knock the fuel loose and cause an explosion. “Protecting the propane tank becomes important—staking it to the ground so it can’t tip over or putting a barrier around the tank so no one can get near it,” he notes.

Despite the concerns surrounding propane as a tent-heating source, Etzel estimates that seven out of 10 events still use propane.

Diesel can serve as a cost-conscious alternative to propane in indirect heating, but “there’s just not many of those [units] on the market today,” Etzel says. “Diesel is a little harder fuel to handle, it smells and it’s a little oily if you spill it. But with good care it works just fine.”

When deciding between electric and diesel heaters, it is important that event planners and tent rental companies consider their unique situation, says Daryl Benz, Northeast event sales for Aggreko North America. Electric resistant heat, for instance, often is used in places where flammable sources are not allowed.

“Many fire inspectors and security teams insist on electric heat, which can be used in both indoor and outdoor applications without risk of fuel spills or emissions,” Benz says. “Electric heat is the cleanest heat out there since there are no fumes or particulates coming out of that heater whatsoever.”

He adds that if utility power is available at the site, “then electric heat becomes even more efficient. You don’t have any diesel fuel to burn, and you don’t have any propane to refill.” If there is not a utility source, then an electric heater can be combined with a generator to effectively heat the space.

Benz cites several factors to be considered when determining which heat source to use, such as security concerns, fire department regulations, venting of gas, proximity of equipment and site access for refueling. “It’s important to have a rental utility partner who knows how to evaluate all facets of a tented event to make the best possible decision,” Benz says.

Because electric heaters are housed in a protective cabinet and don’t burn fuel or emit fumes, they can be placed within the tent. However, the fire marshal’s office will make the final call on whether such placement is allowed. As Benz puts it, “Like any heat source, it is a best practice to make sure flammable items like pipe and drape, decorations or even paper goods are kept a safe distance away from the heating system.”

How much heat do I need?

“There is a lot that goes into determining how much temporary heat is needed depending on the location and the time of year,” Benz says. “Heating a 40-by-60-foot tent in Virginia in December is going to be a lot different than heating that same sized tent in Maine in December.”

Benz advises that when designing a heating system for a large tent, “you want to make sure you maintain a certain temperature, especially with snow loads. Also,
it’s always good to have more heat than you think you’ll need. For example, doors open and close, and weather changes can affect heating efficiency.”

The type of event is another important consideration. “If you have a black-tie event and the ladies are wearing the perfect black dress, you have to put a little more heat into the tent to make sure everybody is happy,” says Tony Tauer, president of American Event Services in Danville, Ill. “If it is an event that has a BMX track inside and everyone is hot and sweaty, then there doesn’t need to be so much heat.”

Many of the heater manufacturers will provide a chart or other documentation that shows the preferred amount of BTUs needed per square foot of tent. To ensure guest safety and comfort, the SEC Group will add 25 percent more heat to the recommended output. “If you are behind with heat power, you will never catch up,” Etzel cautions.

To make the most of heating, Phillips also advises keeping obstructions away from the tent. “Another important consideration is to keep an eye out for changing weather conditions that may affect the sizing of the heating requirements,” he says.

In the winter, “changing weather conditions” often translate into snowfall. Etzel says that the tent’s surface temperature should be above 50 degrees to keep the snow from sticking to the roof. Maintaining that temperature in freezing conditions means more heat is necessary. “In those situations, I would add 25 to 50 percent to my heat power just to make sure the tent never got below 50 degrees,” he says.

In the event of heavy, quickly accumulating snowfall, Tauer recommends that the tent company or event planner have someone on-site who can help remove snow from the tent if necessary. Other ways to improve heating efficiency and accelerate snowmelt include using a liner to create a barrier at the top of the tent, fastening sidewalls to the ground and installing a quality door system with tight closure.

Finding a home for heaters

In terms of placement, heaters should run along the side of the tent, with ductwork blowing heat through the bottom of the tent. Etzel says that units should be placed about 20 to 40 feet apart since that is how far the heated air will reach. A 100-foot-wide tent would need heaters on either side of the structure. Etzel also notes that heater units should be 10 feet from the tent for most code regulations; some, however, require 20 feet.

Heating specialists often hear concerns from event planners and tent rental companies that ductwork and heating equipment will affect the look of a tent. To that end, Atlas Sales and Rentals will employ a variety
of methods to keep interference to a minimum. For heaters fired by natural gas, propane
or diesel, these options include:

  • Placing heating diffusers under the walls of the tent.
  • If floor is raised, installing ductwork underneath the floor.
  • Running heating ducts off the main supports
    of the tent.
  • Providing cable ramps
    to prevent trip hazards.
  • Inserting duct adapters that interconnect with the walls of the tent.
  • Locating heating equipment in the least visible location (i.e., the back side of the tent, or behind bushes or other obstructions).

Sometimes, the desires of the event planner and the heating needs of the tent don’t mesh. “The decorator wants everything to look perfect for the customer, and the HVAC person is trying to keep everyone warm and happy inside,” Tauer says. “It is the responsibility of the HVAC guy or gal to speak up if something won’t work. You just have to work together.”

Holly O’Dell is a freelance writer based in Joshua Tree, Calif.

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