Who better to ask about choosing temporary heaters than someone who has been in the construction business for more than 30 years? Tapping into that kind of experience, Larry, a Construction Superintendent at Holdsworth Klimowski, shares his thoughts on selecting heating units.
“Of course you want reliability and serviceability,” Larry says. He opts for heaters that are simple to set up, use, and maintain. Larry has been known do minor repairs over the phone with Babfar. “I worry less about materials or the building freezing if I know that I can get a technician on the first call and, if needed, that they’ll be on site within the day.”
But Larry’s biggest recommendation is to choose a heater that uses outside air.
“Some heaters are placed inside an enclosure,” reflects Larry. “Those heater manufacturers try to tell you their units are fine for inside use. But, I have had problems when a heater’s combustion is inside the building.”
Beyond the safety issues related to carbon monoxide levels, re-burning the inside air causes other problems for Larry.
“I prefer to pressurize the building, using a large volume of fresh, outside air,” says Larry. Heaters that force outside air into a building prevent the infiltration of cold, outside air. Smaller, re-circulating heaters do the opposite. By re-heating inside air, the heater allows cold air to seep in from openings all over the building.
“Plus, I have had problems with these heaters contributing to the carbonation of concrete,” adds Larry. Carbonation is the result of carbon dioxide (CO2) in the ambient air settling near the floor and interfering with hydrating cement. Exhaust from heaters placed inside the building adds CO2. Shortly after pouring a slab, for example, flakes or dust may be visible on the surface. Over time, carbonation can penetrate deeper into the concrete and threaten its strength and durability.
“Heaters that use outside air distribute existing CO2 and prevent carbonation,” says Larry. “In addition, since these heaters usually are placed outside the building, their exhaust doesn’t increase CO2 levels inside.”
Another benefit of pressurization is related to temporary windows. Often contractors install temporary panels or poly over window openings. “Positive pressurization counter-balances outside winds to hold the materials in place,” says Larry.
So, there are several reasons for using heaters that use outside air. But how do you know you will get a good air exchange? “You have to look at the size of the blowers on the heating units,” answers Larry. “Bigger blowers have a higher cubic feet per minute (CFM) rating and can push air to the far end of the building.”