The Chimney Balloon

March 09, 2009
March/April 2009
A version of this article appears in the March/April 2009 issue of Home Energy Magazine.
Click here to read more articles about Heating
Most homeowners like to have the option
of using the fireplace once in a while.
I operate Grading Spaces LLC, Home Inspection and Performance Analysis, serving residences in southern Wisconsin since 2002. It’s the typical one-stop-shop, whole-house inspection service. Grading Space’s success is due in large part to an educate-the-homeowner approach that involves a detailed reporting method that I developed over time. Half of my time is spent educating homeowners. This is the most exciting part of the job to me, because I am imparting information that seems obvious and yet is enlightening. The information is presented in such a way that clients can easily prioritize their energy upgrade decisions. Most homeowners appreciate having an independent and objective source of information available to them, one that is not trying to sell them on any particular product, but rather gives them information that can help them to get the best value for their dollars.

Last year I was hired by Jason Raddenbach, a manufacturer’s rep for Chimney Balloon USA, to perform a blower door test on his home, using the Chimney Balloon, in order to measure the capability of this European fireplace flue sealer. Air sealing, along with properly insulating the building shell, is one of the most cost-effective ways to keep heated (or cooled) air inside a structure, thus saving energy and increasing occupant comfort. I often don’t suggest ways to seal the fireplace flue when I do a typical home inspection, because homeowners usually tell me that the fireplace is used “sometimes.” This makes it difficult to prescribe a permanent means of air sealing the flue. Most homeowners like to have the option of using the fireplace once in a while. This job was to measure what happens when a removable inflatable damper is inserted into a client’s fireplace flue.

What Is a Chimney Balloon?

A British plastics engineer named David Woodman invented the Chimney Balloon in 1989. While he was working in his drafty study on a windy winter day, his fireplace flue stuffed ineffectively with crumpled-up newspapers, it occurred to him that a specially designed balloon could be fitted into the fireplace to stop the draft. The balloon membrane had to be durable enough to withstand the acidic and corrosive environment of the chimney, but supple enough to grab tightly to the uneven surface of the flue wall. He solved the problem by using a proprietary polylaminate that had the chemical characteristics needed for what he christened the “Chimney Balloon.”

The manufacturers claim that the Chimney Balloon stops drafts, heat loss, chimney smoke crossover, and insect entry, and reduces outside noise infiltration through the flue. Special adaptations of the Chimney Balloon have been used to plug HVAC vents and skylight chutes. It comes in ten standard sizes (prices range from $42.99 to $53.99) to fit a variety of common American stoves and fireplaces. Custom sizes are also available, fitting anything up to a cavernous 3 foot x 6 foot fireplace flue.

The Chimney Balloon is basically an inflatable balloon. There’s a valve on the bottom of the handle that resembles a gas spigot. To inflate the balloon for insertion into the flue, you blow it up and close the valve. To remove, open the valve and deflate the balloon. The balloon membrane is designed to deflate if you accidentally light a fire under it. If you use the fireplace regularly, you can keep the balloon somewhere out of the way—on the woodpile, for example, or in a paper bag next to the fireplace.

The Testing Ground: Jason Raddenbach’s Home

Jason’s home is a 1,100 ft2 ranch style in Janesville, Wisconsin, purchased in 2003. The home is relatively well insulated, with R-50 cellulose blown into the attic and R-9 fiberglass batts in the walls. The living room has a prefab fireplace (Majestic L36B Prefab Zero Clearance) with a flapper-style downward-opening metal damper and a 9-inch flue. The fireplace has Sears Brand bifold tempered-glass doors.

Jason had upgraded his house with new insulation in 2004. I did a preliminary scan of the home with my IR camera and noticed a spot on the ceiling, showing that an area of insulation had been missed during the upgrade. It turned out to be a very difficult spot to reach and correct, but overall the home was reasonably tight.

The Raddenbach home is heated with natural gas. It has been occupied by the same family, and served by the same gas utility, since 2003. Table 1 shows natural gas consumption per heating year, October through March, for the past five years.

I tested the Raddenbach home in August 2008, using a Minneapolis Blower Door Test System. The home was depressurized to 50 Pa and air loss measurements were recorded in CFM. First I tested the home with the damper wide open, to see how the home would perform in a worst-case scenario. Then I closed the metal damper and retested the home. I tested again with the glass doors closed and again with both the damper and the glass doors closed. Finally, I tested with a 9 inch x 9 inch Chimney Balloon installed. The Chimney Balloon was quite effective, as the results show (see Table 2).

Using a Chimney Balloon made the home 27% less leaky than it would have been without a damper; 15% less leaky than it was using the damper only; and 6% less leaky than it was using the glass doors and the damper.

Energy is lost through open chimney flues in many homes, both when a fire is burning and when the fireplace is not being used. Air sealing is one of the most cost-effective ways to keep heated (or cooled) air inside a structure, as I explained above. Chimney flues, however, are often not air sealed. The Raddenbach house was tested to assess the effectiveness of the Chimney Balloon in sealing off this potentially large energy loss.

The results show that the Chimney Balloon achieved an improvement of 27% over the worst-case all-open scenario. The damper and doors on this fireplace were in good condition and worked relatively well; however, many of the fireplace components that I inspect are not in good condition, and will contribute much less to air sealing the home.

Installing the Chimney Balloon might occasionally pose a problem. To be honest, I have never installed a Chimney Balloon. Since I was working on the home of an expert, Jason handled installation and removal. But I have inspected a lot of chimneys. Some hearth designs and damper arrangements make it difficult to get under the flue, and installing the balloon in those chimneys might take some finesse. The balloon comes with an 8-inch handle, as described above, but a handle extender can be purchased to make insertion and removal easier.

It also takes a bit of work to get the Chimney Balloon out if you want to use the fireplace. In general, the best way to deal with a fireplace that is used frequently is to install an EPA-approved sealed-combustion unit, or wood-burning stove insert, into the masonry opening. However, these inserts are so expensive that you should probably view them as a last resort. The fact that the Chimney Balloon is inexpensive and gets quick results is appealing to most clients I talk to, especially once I tell them that an insert can cost $3,000 and up.

I actually saw a Chimney Balloon for the first time a few years back, but I didn’t really think about it until Jason contacted me. After running the test, I realized that it’s a quick, inexpensive solution for the drafty-chimney syndrome I see all the time. If I hadn’t done the blower door test in the various configurations, I probably wouldn’t have become a fan, but that’s what I like about this business; the solutions are based on testing, and on the application of building science. Often the solutions are remarkably simple and make perfect sense—once you do the testing and apply the science.

Mark Furst has been involved in the construction industry in some capacity for 30 years, beginning as a designer and contractor of structures at Renaissance Festivals all around the country and then moving into more conventional remodeling practice. While nursing an aching back some years ago, he discovered that there was a living to be made looking at and writing about buildings, rather than having to actually build them! In 2000, Grading Spaces was born, at first offering “regular” home inspections (for real estate purchases) but then moving into energy efficiency and home performance testing, which now occupies the bulk of Grading Spaces’ business.

For more information:
For more about Grading Spaces LLC, Home Inspection and Performance Analysis, go to or phone Mark Furst at (920)563-7480.

For more on Chimney Balloon USA, go to, or phone (608)467-0229. Wholesale pricing is available.
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