The fireplace doesn't have a chimney. Is that alright?

Monday, October 8, 2018

We are seeing more ventless fireplaces, also known as “duct-free” fireplaces, in Gainesville homes over the last few years. They have several advantages over a regular fireplace:

  • Nearly 100% energy efficiency. A traditional, ducted fireplace, sends much of the heat up the flue/chimney, while a ventless fireplace retains the heat in the home.
  • Releases less harmful gases than some other heating alternatives.
  • Builders like them because they don’t have the design limitations or additional cost of configuring a flue to the exterior. A ventless fireplace can be located almost anywhere in the home.

   However, there is a downside to the convenience and ease of installation. Here’s an excerpt from an article about the controversy regarding  the safety of ventless fireplaces by the International Association of Certified Home Inspectors (InterNACHI):

Despite their name, they vent unburned combustion byproducts directly into the living space. Traditional fireplaces, by contrast, are equipped with a flue that vents to the outdoors, saving humans and their pets from exposure to the bulk of the carbon monoxide (CO) and airborne particulates created by the fire. As a less serious yet still important side note, ventless fireplaces create high levels of water vapor, which can lead to mold growth and a variety of other moisture-related building problems. Mold can be a serious health hazard for at-risk individuals, and it can damage fabric, photographs, books and building materials.

    To mitigate CO dangers, manufacturers instruct customers to keep a window open while ventless fireplaces are in operation –- advice that is easy to ignore, as an open window allows the entry of cold air, defeating the efforts of the fireplace to warm the living space. Many manufacturers also install an oxygen-detection sensor (ODS) in their ventless fireplaces that will automatically shut down the appliance if oxygen levels in the home become dangerously low. Critics point out that this sensor is typically located at the lower part of the unit near the floor, where it detects cool, fresh, oxygen-filled air and misses hot combustion gasses as they rise and pool toward the ceiling. And if the sensor fails, any CO-producing abnormality experienced by the fireplace will continue unnoticed and potentially harm building occupants.

   Massachusetts, California, and a number of other states in the U.S., as well as Canada and other countries, have outlawed ventless gas fireplaces due to the aforementioned safety concerns. Many individual municipalities, too, have outlawed these appliances in states where they are otherwise legal. 

   The U.S. Department of Housing and Urban Development bans ventless fireplaces in their housing, and advisements against the use of these appliances have been issued by various watchdog groups, such as the American Lung Association, the Centers for Disease Control, the Environmental Protection Agency, and even the Mayo Clinic. 

    In particular, these organizations warn against exposure of individuals who are particularly vulnerable to CO, namely, the elderly, pregnant women, small children, those with pre-existing cardiovascular difficulties, and small pets. To be fair, though, there have been no documented cases of fatalities caused by ODS-equipped ventless fireplaces, according to the U.S. Consumer Product Safety Commission.

   In summary, ventless fireplaces, while attractive and portable, suffer from a design flaw that may allow dangerous gases to enter the living space.

   By the way, not all fireplaces without chimneys are unvented. There is a type of manufactured fireplace, specifically for use with a gas log, that uses a blower to exhaust the combustions gases out a wall vent.

    Also, if it is an older house, the chimney may have been abandoned and removed down to below the roof sheathing in the attic. See our blog post Why would an old, pre-1970s house have a fire place but no chimney on the roof? for more on this.

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 does the house have a chimney but no fireplace?

Why is the chimney leaning away from the house? 

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

   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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