If you’re living aboard or cruising the UK’s canal network, your log burner is probably your main source of comfort during colder months. But if smoke is billowing back into your cabin instead of up the chimney, you might be experiencing downdraft—and it can be a real problem.

Downdraft occurs when air flows down the flue instead of up, pushing smoke and fumes back into your boat. This not only causes discomfort but can also be a serious safety risk. Luckily, there are a few straightforward ways to reduce or even eliminate downdraft in your narrowboat stove.

1. Fit a Proper Chimney Cowl

One of the most effective solutions is to install a rotating or anti-downdraft chimney cowl. These are specially designed to encourage upward airflow and reduce turbulence around the chimney top—especially useful on windy days or when moored in sheltered areas.

Recommended types:
– H-shaped cowls
– Spinning (rotating) cowls
– Wind-directional cowls

2. Extend Your Chimney

The taller the flue, the better the draw. A short chimney—common on boats for clearance reasons—can struggle to establish a strong upward draft, especially when starting a fire. Consider fitting an extension section to your flue when moored up, especially in winter.

Tip: Always remove or lower your chimney when cruising to avoid low bridges.

3. Warm the Flue Before Lighting

A cold flue can prevent smoke from rising properly. Before lighting your fire, try:

• Burning a piece of newspaper in the stove to pre-warm the flue.
• Using a blowtorch or firelighter near the flue entrance for a few seconds.

Warming the flue helps create a natural updraft and avoids that first rush of smoke into the cabin.

4. Check for Blockages or Soot Build-Up

A partially blocked flue drastically reduces draw and increases downdraft risk. Make sure your chimney is:

• Swept regularly (at least once a season)
• Free of bird nests, spider webs, or creosote build-up
• Properly sealed with no gaps or leaks in joints

A clean flue means a safer and more efficient burner.

5. Improve Cabin Ventilation

Log burners need oxygen to burn well and maintain upward airflow. If your boat is tightly sealed or you’re using extractor fans, it can create negative pressure, drawing air down the chimney.

Add or open a dedicated air vent near the stove. It doesn’t need to be large—just enough to equalise air pressure.

6. Avoid Burning Damp or Green Wood

Wet wood produces excess smoke, which increases the chance of backdraft and soot build-up. Use only seasoned wood with less than 20% moisture content, and store it somewhere dry onboard or under a canopy.

Final Thoughts

Downdraft in narrowboat log burners is a common issue, but with the right setup and a few smart adjustments, you can maintain a clean-burning, efficient stove all season long. A little attention to your flue, fuel, and ventilation can make your boat warmer, safer, and more enjoyable—no matter how chilly the towpath gets.