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How is a factory-built fireplace different from a regular fireplace?

Sunday, October 7, 2018

Gathering around the fireplace on a cold evening is one of the most satisfying rituals of winter in Gainesville. Our customers are evenly divided between the more primal wood-burners--who meticulously follow the steps of the “right” way to build a fire they were taught by their dad--and the no-fuss gas-log aficionados. For the ultimate in effortless fires-starting, some newer gas-log fireplaces come with a hand-held remote that, with a click from across the room, ignite a roaring fire in seconds.

   The traditional site-built fireplace is based on a design by Count Rumford. The Count was born Benjamin Thompson in Woburn, Massachusetts, in 1753. Because he was a British loyalist, Benjamin left abruptly for England in 1776, where he applied his knowledge of thermodynamics to design a smaller, shallower fireplace, with a widely angled back to better radiate heat into the room. Also, he restricted the throat to make the chimney draw smoke more efficiently. 

   Count Rumford’s  designs for an improved fireplace were widely published and, by the 1790s, his “Rumford fireplace” became a state-of-the-art standard, with the principles he established still in use for fireplace design. Incidentally, he spent most of his career as an employee of the Bavarian government, where he received the  title “Count of the Holy Roman Empire.”

   Fast-forward to today: about 75% of all new fireplaces are factory-built units, with components that are easier and less expensive to install than a site-built masonry fireplace. The fundamental difference between the two types of fireplaces is that a traditional fireplace is integral to the structure of the home, whereas a manufactured fireplace is essentially an installed appliance. And, just like a washing machine or a refrigerator, it has a serviceable lifespan--usually 20 to 30 years. 

   The primary component of a factory-built fireplace is a firebox enclosed in a steel cabinet, which is fitted to a steel chimney or flue. The whole assembly is lightweight, inexpensive, and efficient. They are often called “zero-clearance” fireplaces because of the minimal safe clearance distance required around them for installation. An insulating air blanket is a key part of the design that keeps the outer wall of the fireplace cool, and enables the fireplace to be set in close proximity to wood framing.

   All factory-built fireplaces are tested to rigorous standards set by Underwriters Laboratories (UL) and the American Gas Association. They have an excellent safety record when properly installed and maintained; but, like any appliance with an open flame, there are several safety rules to follow to avoid a fire hazard:

  • The fireplace should sit on a non-combustible material. If the floor is wood, then it should rest on a metal or tile panel that extends the length and width of the fireplace.
  • Any combustible flooring must be a safe distance from the fireplace opening.
  • The grilles for inlet and outlet air should be unobstructed.
  • The same fire-safety precautions used for a traditional fireplace should be observed for a manufactured fireplace.
  • Regular maintenance and cleaning are required. The chimney should be inspected monthly during the heating season for creosote buildup (the black, oily residue from wood-burning), and an annual cleaning by a professional chimney sweep is recommended. 

    Also, see our blog posts Why does the house have a chimney but no fireplace? and The fireplace doesn't have a chimney. Is that alright?

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Here’s links to a collection of our other blog posts about FIREPLACES AND CHIMNEYS:

 Is a gas log lighter dangerous?

What is the 3-2-10 rule for masonry chimneys? 

What causes black soot buildup on my gas fireplace logs?

Why is creosote buildup in a chimney dangerous?  

Why is the chimney leaning away from the house?  

   Visit our FIREPLACES AND CHIMNEYS page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

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