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Best Chimney Balloon for an Unused Fireplace: 5 Draft Stoppers That Save Heat
An open, unused fireplace is a hole in the thermal envelope: warm room air escapes up the flue and cold air spills back down. A chimney balloon seals that opening from the inside, and the five picks below cover small flues, large fireplaces, odd shapes and damperless wood stoves. Budget-minded buyers, owners of oversized masonry fireplaces and anyone with a round stove flue will each find a match. The overview table below sorts all five by key spec, best use and price tier, so a decision is possible before the reviews.
The Picks at a Glance
| Product | Key Spec | Best Use | Price Tier |
|---|---|---|---|
| Large Size Chimney Balloon | 14 x 38 in inflatable | Oversized masonry fireplaces | Mid |
| Small Chimney Blocker | 15 x 9 in inflatable | Small flues and tight openings | Budget |
| Herdwick Wool Flue Plug | 5-6 in round flue, wool | Wood stoves without a damper | Mid |
| 14 x 24 in Chimney Draught Excluder | 14 x 24 in inflatable | Standard fireplace openings | Budget |
| THE Chimney Balloon Air Stopper | 14 x 14 in inflatable | Square or compact flues | Budget |
1. Large Size Chimney Balloon, 14 x 38 Inches
Type: Inflatable chimney blocker
Nominal Size: 14 x 38 inches
Intended Use: Large fireplace openings
Reusable: Yes
Installation: Inflate in place
The long 38-inch profile is the reason this pick exists: wide masonry fireplaces that swallow a standard balloon need the extra span to seat against both sides of the flue. The inflatable body squashes slightly as it fills, which helps it grip uneven brickwork, and the whole unit deflates for storage when the fireplace comes back into seasonal use. It suits owners of older, generously proportioned fireplaces who have measured their opening and found it at the top of the normal range.
Who It Suits: Buyers with an oversized fireplace opening and no interest in a custom-made plug. It earns its place as the only large-format inflatable in the lineup.
Trade-off: The wide span means more surface to seat correctly, so an opening that is only slightly too big for a standard balloon may leave this one bunching at the edges.
2. Small Chimney Blocker, 15 x 9 Inches
Type: Inflatable chimney plug
Nominal Size: 15 x 9 inches
Intended Use: Indoor installation
Reusable: Yes
Installation: Inflate in place
The compact 15 x 9-inch footprint targets narrow flues: small Victorian fireplaces, bedroom hearths and openings that a full-size balloon cannot fill without folding over itself. Because the plug is rated for indoor use, it is fitted from the room side, which keeps the job simple for anyone who would rather not climb onto the roof. The low price also makes it a sensible first balloon for a secondary fireplace that sees little use.
Who It Suits: Owners of small or narrow fireplaces, and anyone buying a first plug for a rarely used room.
Trade-off: The small face gives little margin for error on an irregular opening, and it will not bridge a standard-width masonry fireplace.
3. Herdwick Wool Flue Plug for 5-6 Inch Round Flues
Type: Wool flue plug
Material: 100% Herdwick wool
Fits: 5-6 inch round flue
Damper Required: No
Intended Use: Wood stoves and round flues
Origin: Made in England
This is the only non-inflatable pick, and that is its appeal. Dense Herdwick wool is pushed into a round flue and holds itself in place by friction, so there is no valve, no membrane and nothing to puncture. It is designed to work without a damper, which makes it the natural answer for wood stoves and inserts where a balloon has nothing flat to press against. The wool construction also means no rubber smell on first use and no slow deflation over a season.
Who It Suits: Wood stove owners and anyone with a 5-6 inch round liner who wants a plug with no inflatable parts to fail.
Trade-off: Wool is a friction fit, so it is fussier to remove and refit than a balloon, and the round-only sizing rules out rectangular masonry openings.
4. 14 x 24 Inch Chimney Draught Excluder
Type: Inflatable draught excluder
Nominal Size: 14 x 24 inches
Inflation: Mouth tube included
Reusable: Yes
Origin: Made in the UK
The 14 x 24-inch size is the middle of the range and fits a large share of ordinary domestic fireplace openings, which is why it reads as the default choice for most households. A mouth inflation tube is included, so no pump is needed and the balloon can be topped up by breath alone. The revised design suggests the manufacturer has refined the shape since earlier versions, and UK production is a plus for buyers who care where a rubber goods item is made.
Who It Suits: The typical homeowner with a standard masonry fireplace who wants the simplest possible install and a known brand behind the product.
Trade-off: The included tube is the only inflation method, so buyers who find sustained blowing awkward may prefer a pump-based approach.
5. THE Chimney Balloon Air Stopper, 14 x 14 Inches
Type: Inflatable draught air stopper
Nominal Size: 14 x 14 inches
Intended Use: Draft elimination
Reusable: Yes
Installation: Inflate in place
Eliminates cold drafts THE Chimney Balloon Draught Air Stopper, 14 x 14 inch
The square 14 x 14-inch format is built for openings that are close to even in both directions, including compact fireplaces and some flue boxes where a long balloon would crease. Its purpose is narrow and clear: stop cold air coming down the chimney when the fireplace is out of service. The small, near-cubic shape packs down well for summer storage and is easy to handle on a step stool.
Who It Suits: Buyers with a compact or roughly square opening, and anyone who wants a spare plug for a second fireplace.
Trade-off: The square profile leaves gaps on a wide rectangular opening, so it is a poor fit for full-size masonry fireplaces.
Before You Buy
- Size: Measure the flue opening at the point where the balloon will sit, not the fireplace surround; the nominal size must match that opening with a little room to spare.
- Shape: Rectangular balloons suit masonry fireplaces, square plugs suit compact openings, and round wool plugs are for stove flues only.
- Compatibility: A balloon needs a reasonably smooth surface to press against; damperless stoves need a friction plug such as wool.
- Material: Inflatable options rely on a rubberized membrane that can puncture, while wool resists tearing but is harder to clean.
- Care: Wipe inflatable balloons and store them deflated and dry; air wool plugs thoroughly before refitting.
- Storage: All five picks are reusable, so keep the plug and any inflation tube together between heating seasons.
- Included Accessories: Check whether an inflation tube is supplied, since not every balloon ships with one.
Frequently Asked Questions
- Does a chimney balloon work without a damper? An inflatable balloon needs a surface to press against, so a damperless flue is better served by a friction plug such as the Herdwick wool option.
- Can a chimney balloon be left in place all year? It should be removed before any fire is lit and stored dry between seasons; leaving it in permanently risks forgetting it when the fireplace returns to use.
- Which size chimney balloon is needed for a standard fireplace? Most ordinary masonry openings fall in the middle of the range, making a 14 x 24-inch balloon the usual starting point after measuring.
- Is a wool plug better than an inflatable balloon? Wool suits round stove flues and has no membrane to puncture, while inflatables are easier to fit and remove in rectangular fireplaces.
- What happens if the balloon is slightly too small? It will not seal, and cold air will continue to leak around the edges, so sizing up to the next format is the safer choice.
Bottom Line
For most unused masonry fireplaces, the 14 x 24 Inch Chimney Draught Excluder is the top pick: a mid-range size that fits typical openings, an included mouth tube and a design that has been through a revision. Wood stove owners should take the Herdwick wool plug instead, and anyone with an unusually wide or narrow opening can size up or down from the table above.
