Blogs – Temporary Climate Solutions

Understanding the Difference Between Indirect and Direct Heating

When you burn anything, the products of combustion are produced. This includes soot, carbon dioxide and water. The exhaust stack on an indirect fired heater carries these out of the system so these undesirable substances do not enter your space. When you put a fired heater directly into your building and vent the products of combustion into your space, however, you are introducing that soot and carbon dioxide—as well as large amounts of water—into your space. Welcome to a dripping ceiling.

Direct Heater: Low upfront cost, lots of problems down the road

A typical million BTU fired direct heater, for example, creates about 45 lbs. of water every hour. That is the same thing as someone dumping a 5-gallon bucket of water in your building every hour. This is why, when you add direct-fired heat as a temporary climate solution in a space, your windows sweat, and your ceiling drips. With a direct heater, an exposed flame has air blown through it and directly to where it needs to go. Direct heat is dangerous for humans and allows too much moisture to be added to the environment.

Not only is direct heat dangerous for employees, and a problem for the building itself, it’s also more expensive than an indirect heater to operate. For example, a business may purchase a 4 MBTUh direct heater for a very low upfront cost. However, only a fraction of the BTUS would be needed if they recirculated the heat. The low upfront cost is deceptive.

Indirect Heater: A Better, more cost-effective solution

A better option for a temporary climate solution? An indirect heater featuring an enclosed flame.
Indirect heat doesn't have the same problems as direct heat, because the air is processed before it comes into space. An indirect heater uses dry and clean air from outside, instead of dirty wet air. Indirect is significantly more expensive in the beginning, but safer and less costly in the long run.


Polygon Climate Control is putting engineered fit-for-purpose equipment on our customers’ sites for fewer callbacks and enhanced performance to keep projects on schedule! We offer a complete range of services within the areas of temporary climate solutions, document recovery, and emergency drying solutions. Connect with us to discuss more.

Direct Heater:
Low Upfront Cost, Lots of Problems Down the Road

Indirect Heater:
A Better, More Cost-Effective Solution

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