A fireplace that draws fine on a still night and then puffs smoke back into the room when the wind picks up is dealing with downdraft. October is when Bolingbrook homeowners usually notice it for the first time, because that is when the first real fires of the season line up with the first gusty cold fronts. The good news is that wind-driven downdraft almost always has a physical cause at the top of the chimney, and most of those causes can be fixed.
By James Rodriguez, Central Chimney Service.
What downdraft actually is
Downdraft is air moving down the flue instead of up it, pushed by wind pressure at the chimney top. A chimney works because warm flue gas is lighter than the outside air, so it rises and pulls fresh air in through the firebox. Wind blowing across or against the top of the flue can overpower that gentle lift, especially before the flue has warmed up.
Why it gets worse on windy days specifically
Wind creates zones of high and low pressure around a house. When a gust hits a roof or a taller neighboring structure and rolls over it, it can create a pocket of higher pressure right at your chimney outlet. If that pressure is higher than the pressure inside the firebox, air goes the wrong way. When the wind dies down, the draft recovers, which is why the problem seems to come and go.
The most common causes we find
In our experience the cause is nearly always at the roofline: chimney height, what surrounds it, or what is (or is not) sitting on top of it.
A chimney that is too short for its roof
Chimneys that barely clear the roof sit inside the turbulent air that tumbles over the ridge. Additions, second-story build-outs, and taller replacement roofs can all leave a chimney that used to be tall enough now sitting in that dead zone.
Nearby obstructions
Mature trees, a taller section of the same house, or a neighboring two-story wall a short distance upwind can all deflect gusts straight down onto the flue outlet.
Missing or wrong cap
An open flue with no cap is exposed to wind from every direction. A standard cap helps, but a flue in a genuinely windy spot may need a cap designed to use the wind to help draft rather than fight it. You can read more about the options on our chimney caps and crowns service page.
Two flues side by side
When a fireplace flue and a furnace or water heater flue end next to each other at the same height, exhaust from one can be drawn down the other on a gusty day. Separating the outlets or adjusting their heights usually solves it.
What you can try before calling
A few habits reduce downdraft while you work out a permanent fix. None of them replaces finding the cause.
- Warm the flue first. Hold a rolled sheet of newspaper, lit, up near the open damper for a minute before lighting the main fire.
- Crack a window on the side of the house the wind is hitting. That raises the indoor pressure slightly and helps the flue win.
- Build smaller, hotter fires on the windiest nights rather than a large smoldering load.
- Make sure the damper is fully open and the ash level in the firebox is low.
Our DIY chimney care guide covers these steps and other safe homeowner checks in more detail.
When downdraft is a safety issue
Smoke rolling into the room means combustion gases are coming with it, including carbon monoxide. If a gas appliance shares the area and you notice soot around a fireplace opening, a smell of exhaust near the furnace, or a CO alarm going off on windy days, stop using the fireplace and have the system looked at. That pattern can mean appliance exhaust is being pulled back into the house, not just wood smoke.
How we diagnose it in Bolingbrook homes
We start on the roof: chimney height relative to the ridge and anything nearby, the cap, the crown, and where every flue outlet sits. Then we check the firebox, damper, and smoke chamber from inside, and we look at the house itself, because a tight home with strong exhaust fans can make wind problems much worse. We work to NFPA 211, the standard we follow for chimney inspections, so the visit includes the clearance and condition checks that standard calls for. If a camera look at the flue is needed, we will tell you why before we do it.
Homeowners across our Bolingbrook chimney sweep service area can book an inspection and get the price up front before any work starts; current rates are on our pricing page. We are insured and bonded, and James has been doing this work in the area for 29 years. Call (815) 305-5510, seven days a week from 7 AM to 7 PM.
Frequently asked questions about chimney downdraft
Why does my fireplace only smoke when it is windy?
Wind creates pressure at the chimney top that can push air down the flue. When the gusts stop, normal draft returns, so the smoking comes and goes with the weather.
Will a chimney cap stop downdraft?
A cap helps by blocking wind from blowing straight into the flue. Chimneys in very exposed spots sometimes need a wind-directional cap rather than a basic one.
Can a chimney be too short?
Yes. A chimney that barely clears the roof sits in the turbulent air rolling over the ridge, which makes it prone to downdraft.
Do trees near the house affect my chimney draft?
They can. Tall trees upwind of the chimney can deflect gusts down onto the flue outlet, especially once they grow taller than the chimney top.
Is smoke coming back into the room dangerous?
It can be. Smoke carries carbon monoxide and fine particles, so persistent spillage should be diagnosed and not simply tolerated.
Does opening a window really help with downdraft?
Often, yes. Cracking a window on the windward side raises indoor pressure slightly and gives the fire a supply of air, which helps the flue draw.
Can the furnace flue pull smoke from the fireplace flue?
When two flues end side by side at the same height, wind can pull exhaust from one outlet down the other. Adjusting or separating the outlets usually fixes it.
How do I get a downdraft problem diagnosed?
Call (815) 305-5510 to book an inspection. We check the roofline, cap, flues, and house pressure and quote any fix up front.
Published October 15, 2026