Chimney and fireplace symptoms
Cold air pours out of my fireplace when it is not in use
Cold air falling out of an idle Portland fireplace often means the throat damper does not seal or is missing, leaving the flue open to the sky. It costs heat but is not a fire hazard, and a top-sealing damper closes it.
Updated
What to do right now
Check that the damper is actually closed; a poker handle left in the open notch after the last fire is often the answer. If it is closed and the draft continues, this is a comfort problem rather than a hazard, and a rolled towel across the opening holds until we come. Leave the clamp on a gas log damper alone; that one is meant to stay open.
Likely causes, most common first
Each of these turns the flue into a cold air pipe, and the way the draft behaves points to which one you have.
- Most common
The throat damper closes but does not seal
The sign: Cold air through the gap around the plate's edge, daylight or a warped rim in the flashlight beam, and a firebox back wall as cold as the yard.
The fix: A top-sealing damper, a gasketed lid on top of the flue worked by a cable from below, seals far better than a cast iron plate. Damper Repair and Replacement, from $149
- Common
There is no damper, or it was removed for gas logs or an old insert
The sign: A flashlight straight up shows the flue or the sky with no plate across it, or a bare frame with the plate gone.
The fix: A top-sealing damper goes on the flue top where no throat damper remains, or glass doors where a gas log set needs the flue kept open. Damper Repair and Replacement, from $149
- Common
Wind is pushing down an uncapped flue
The sign: The draft comes in gusts on windy days, east wind days especially, with a puff of soot smell and ash lifting off the grate.
The fix: A cap breaks the downward push, and a wind-directional cap handles a chimney that sits below a ridge or taller trees. Chimney Cap Installation, from $299
- Less common
The house itself is pulling air down the flue
The sign: The draft is worst on still, cold nights, strongest in a basement or ground-floor fireplace, and eases when an upstairs window is closed.
The fix: A draft test with the house closed up shows where the warm air is leaving, and sealing the idle flue and the upstairs leaks follows. Chimney Inspection, from $129
Two minutes of safe checks
Two minutes at the hearth tells you whether the damper, the wind or the house is letting the cold in.
- Hold a strip of tissue at the top of the fireplace opening with the damper closed: tissue pushed steadily into the room is a leaking damper, while tissue that jumps in gusts is wind down the flue.
- Shine a flashlight at the closed plate and look for daylight at its edges, a bowed rim, or no plate at all.
- Touch the firebox's rear wall: as cold as the outdoors with the damper shut means the flue above is open to the weather.
- Note the weather when it is worst; calm, cold nights point to the house's own stack effect, and east wind days point to the cap.
Why a closed throat damper still lets cold air in
A throat damper is a cast iron plate dropped into a cast frame with no gasket; even new it leaves a gap around its edge, and rust and warping widen that gap over time.
Warm room air leans against that gap all winter. Heat rises through the house, and the pressure that pushes warm air out at the top pulls cold air in at the bottom through the easiest opening it can find, and a fireplace flue is the easiest.
A top-sealing damper is a gasketed lid on the flue's top, spring-loaded shut and opened with a cable reaching down to the firebox. It seals far better than any throat plate, keeps rain and animals out, and the flue above the firebox no longer holds a column of outdoor air.
East wind days in Troutdale, Gresham and east Portland
On east wind days, a flue in Troutdale, Fairview, Gresham or east Portland takes a downdraft no throat damper stops. Pressure building east of the Cascades drives that cold air west through the Columbia River Gorge, hardest along Interstate 84.
While an east wind blows, an uncapped flue delivers cold air in pulses, with ash and soot smell riding along. A cap with a solid lid and screened sides turns the gust aside, and a wind-directional cap, which swivels to put its back to the wind, suits a chimney hemmed in by a ridge or trees.
Wood Village and the rest of east Multnomah County get the same, as does any chimney with open ground toward the Gorge. On these chimneys a top-sealing damper matters most, because the wind leans on a leaky throat plate for hours at a time.
Glass doors, chimney balloons and the fixes that last
Here is what each common answer to a cold fireplace does, from stopgap to permanent.
| Option | What it does | Where it fits |
|---|---|---|
| Glass doors | Slow the air moving through the opening and keep the draft off your ankles, but they are not airtight and the flue behind them stays full of outdoor air. | Alongside a leaky damper; not a substitute for one that seals. |
| Chimney balloon or foam plug | Blocks the flue below the damper while it is in, but a fire lit under one fills the house with smoke. | A stopgap only, with the warning tag kept visible. |
| Top-sealing damper | Closes the flue top with a gasketed lid, installed in a single visit, with the cable and handle fitted in the firebox. | A throat damper that leaks, or a flue with no damper at all. |
| Cap | Turns wind aside at the flue top; a sealed cap with no openings retires a flue nobody will use again. | Wind down the flue, fitted at the same visit as a damper when both are needed. |
| Draft test | We test with the house closed up and show you where the warm air is going. | A fireplace that is only the exit for air the house is losing somewhere else. |
Cold draft from the fireplace: common questions
Why is cold air coming from my fireplace when the damper is closed?
Because a throat damper closes without sealing. The plate rests in a cast frame with a gap around it, rust and warping widen the gap, and warm air leaving the upper house pulls cold air in through it all winter. A flashlight at the closed plate often shows daylight at the edges, and a top-sealing damper is what closes it.
Is a top-sealing damper the fix for a cold draft from the fireplace?
When the damper is the leak, yes. It sits on top of the flue as a spring-closed gasketed lid with a pull cable down in the firebox, and it seals where a cast iron throat plate cannot. It also keeps rain and animals out. Wind pushing down an open flue while a fire burns is a different problem, and that one takes a cap.
Will glass doors stop the cold draft from my fireplace?
They reduce it without stopping it. Glass doors are not airtight, so air still moves through the frame, and the flue behind the doors stays full of cold outdoor air that chills the firebox and the wall around it. They pair well with a top-sealing damper and stand in for one when a gas log set needs the flue left open.
Are chimney balloons safe for stopping cold air from the fireplace?
Safe as long as nobody lights a fire under one. An inflatable plug blocks the flue below the damper and stops the draft, but a fire lit with it in place fills the house with smoke and can melt the plug into the flue. If you use one, hang its warning tag in plain sight in the firebox and take it out before the first fire of the season.
Why is the cold draft from the fireplace worse on windy days?
Because wind across an uncapped flue pushes air down it in gusts, and a damper that leaks a little in calm weather leaks a lot under pressure. In the east metro the Gorge wind can do this for hours at a stretch in winter. A cap turns the gust aside, and a top-sealing damper closes what the cap cannot.
Related pages
Areas we cover for this
Calls about cold draft from the fireplace come in from Rose City Park, Tualatin, Arbor Lodge and Overlook and every other part of the metro we serve.
Ready to book a sweep?
Call with what the fireplace is doing, or text a photo of the opening and one of the chimney top, and we will name the service and its posted price before we come out.