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Cold Draft From a Fireplace You Rarely Use: Causes and Options
A fireplace is an opening to the outside, and even when it sits unused it can leak air into the room. Here are the usual reasons, what to check, and the options for reducing it.
Why the room feels drafty
A chimney is a vertical passage that ends outdoors. Anything that lets air pass between the room and the top of the flue will show up as a draft in the fireplace. The usual suspects are:
- A damper that is open or does not seal. The U.S. Department of Energy advises keeping the damper closed unless a fire is burning, because an open damper causes drafts and heat loss, and suggests checking the seals around the flue damper. A damper that is warped, rusted or worn may not close tightly; see rust in the damper and firebox and damper repair and replacement.
- Wind. Home-inspection training material notes that chimneys should be high enough to prevent downdrafts caused by wind, and that flue size relative to the fireplace opening matters for draft.
- A missing or damaged cap. An uncapped flue top is open to wind, rain and animals; see choosing a chimney cap.
- Unused openings. CSIA inspection guidance recommends sealing unused thimble openings found during a camera scan; see unused flues and fireplace openings.
What to check first
- Is the damper fully closed, and does the handle or rotary control actually move it?
- Does the draft change with the wind, or is it constant?
- Do you also have damp smells, water stains or animal sounds? Those point to a cap, crown or flashing issue; see why is my chimney leaking and animal noises and nesting.
Do not light a fire to test the draft if the damper is stuck or you cannot tell whether the flue is clear.
Options for reducing the draft
| Option | What it does | Points to weigh |
|---|---|---|
| Repair or replace the throat damper | Restores the existing damper to close properly | A throat damper does not seal the top of the flue |
| Top-sealing damper | A damper mounted at the top of the flue that closes onto the liner and is operated by a cable from the firebox | It must be opened before and stay open during any fire until the fire is completely out; the cable eventually needs replacing |
| Glass doors | Cover the fireplace opening | The Department of Energy suggests tempered glass doors along with a heat-air exchange system that returns warm air to the room |
| Plugging and sealing the flue | Blocks the flue when the fireplace will not be used | The Department of Energy advises consulting an expert; a plugged flue must not be forgotten when someone later wants to use the fireplace, see using a fireplace after long disuse |
| Cap | Covers the top of the flue | Keeps out rain, animals and debris but is not a damper; see caps and chase covers |
About top-sealing dampers: a trade-publication installation article describes a metal frame fixed to the top of the flue liner with a stainless steel control cable running down to the firebox, and a fusible link that releases the damper if there is a chimney fire. It also warns that closing the damper while embers are still burning lets carbon monoxide into the house, and that the cable will need replacing eventually. A professional can tell you whether this type of damper suits your flue; see also liners, since the damper attaches to the liner.
Carbon monoxide: never close any damper, top-sealing or throat, while a fire or embers remain. See carbon monoxide and your fireplace.
Frequently asked questions
Will closing the damper fix a cold draft?
If the damper was open, yes; the Department of Energy advises keeping it closed unless a fire is burning. If it is already closed and you still feel air, the damper may not seal or the cause is elsewhere.
Is a top-sealing damper better than a standard damper?
It seals at a different place, at the top of the flue rather than at the throat. Whether it is the better choice depends on your chimney, which is something to discuss with a professional.
Can I stuff something up the flue?
We do not recommend it. Anything blocking the flue can be forgotten and then cause smoke and carbon monoxide to enter the home if someone lights a fire. Ask about a purpose-made solution instead.
Next step
Request a visit or call (862) 225-6529. We can check the damper, cap and flue and talk through your options. AM Chimney Sweep is a registered (NJ HIC #13VH14312300) and insured New Jersey home improvement contractor.
Sources
- U.S. Department of Energy, 5 ways to maximize your fireplace and chimney efficiency (keep damper closed unless burning, check damper seals, plug and seal an unused flue with expert help, glass doors)
- Journal of Light Construction, Installing a flue top damper (how a top-mounted damper works, cable, fusible link, carbon monoxide caution)
- InterNACHI, How to Inspect Fireplaces, Stoves, and Chimneys (wind downdrafts, flue size and draft)
- CSIA, Level 2 Inspection of a masonry chimney (sealing unused thimble openings)