Why a narrowboat feels colder than a house

Steel is a wonderful material for a boat and a terrible one for keeping heat in. A bare steel hull will pull warmth out of the cabin faster than almost anything else, and because a narrowboat sits in cold water on three sides, it loses heat downwards as well as through the walls and roof. Add single-glazed windows, a few unavoidable gaps around the hatch and vents, and a long, thin cabin with the stove at one end, and you can see why winter aboard takes a bit of planning.

The good news is that a well-insulated, sensibly heated narrowboat is genuinely cosy, even when the canal has a skim of ice on it. The trick is to deal with insulation first, heating second, ventilation third — in that order. Get it the wrong way round and you will spend a fortune on fuel while still feeling chilly and damp.

Insulation is the foundation

If you are fitting out or refitting, spray foam applied directly to the bare steel is the gold standard. Around 25mm to 50mm gives you both thermal insulation and a vapour barrier, and it seals awkward curves behind the gunwales that batts simply cannot reach. Older boats often have rockwool, fibreglass or foil-backed foam boards behind the tongue-and-groove, which is fine if it is dry and has not slumped.

• Check for gaps behind cupboards, under the floor and behind the bed — cold bridges here create damp patches and draughts.
• Insulate the floor if you can. Cold rising from the baseplate is the single most common complaint in winter.
• Secondary glazing using acrylic sheet or cheap plastic film over portholes and windows makes a noticeable difference for very little money.
• Curtains and thermal linings should be drawn at dusk, but kept clear of the stove and any flue.
• Draught-proof the hatch with brush or rubber strip, and fit a removable cover over the front doors at night.

Choosing your heating

Most liveaboards end up with two heat sources: a main system and a backup. That redundancy matters when a fuel run is delayed or a part fails in January.

• Solid fuel stove — the classic. A small multifuel stove on a well-insulated boat will heat the whole cabin comfortably. It is dry heat, it works when the electrics are down, and you can cook on it. Keep a good stock of smokeless fuel and seasoned logs, and learn to damp it down overnight.
• Diesel-fired central heating — a boiler feeding radiators or a matrix heater gives even warmth throughout, and is easy to run on a timer. It does need a healthy battery bank and a clean fuel supply, so service it before the cold arrives.
• Gas heaters — convenient, but a flueless catalytic or cabinet heater produces a lot of water vapour and demands serious ventilation. If you use one, it must be room-sealed or correctly flued, never improvised.
• Electric heating — useful on a shoreline, expensive off it. A small oil-filled radiator or a low-wattage tube heater under the bed is a good investment for shoulder seasons.

Whatever you choose, keep the stove flue swept, use dry fuel, and never block the permanent ventilation. A carbon monoxide alarm in the cabin, and ideally a second one near the sleeping area, is not optional.

Ventilation and condensation control

Here is the counter-intuitive bit: to stay warm and dry, you need to let cold air in. Cooking, showering and simply breathing put litres of moisture into the air every day. On a sealed steel box, that moisture condenses on the coldest surface it can find — usually the hull sides behind the bed, the window frames and the underside of the ceiling.

• Keep low and high vents clear. Cross-flow ventilation from a floor-level vent to a roof mushroom or Houdini hatch is what actually dries a boat out.
• Use an extractor over the hob and in the shower, and run it for ten minutes after you finish.
• Wipe down window frames and cold hull surfaces each morning with a cloth, and wring it out over the side.
• Leave cupboard doors and locker lids ajar in the daytime so air can circulate behind them.
• Dry washing outside or in a launderette whenever possible. Indoor drying is the fastest route to black mould.
• A small dehumidifier on a shoreline works well; chemical moisture traps are better than nothing when cruising.

Keeping warm without burning everything you own

Small habits add up. Heat the cabin you are in, not the whole boat — close the doors to the bedroom during the day and warm it an hour before bed. Fit radiator reflector panels behind radiators on the hull side. Use a hot water bottle, a good duvet and a fleece blanket rather than running the stove flat out at 2am.

Layered clothing beats a single thick jumper, and a pair of thick socks and slippers on a cold floor is worth more than an extra degree on the thermostat. If you are cruising in winter, remember that water taps and Elsan points are thinner on the ground, and ice on the canal can trap you for days, so keep the water tank topped up whenever you pass a working point.

A safe winter routine

Test your carbon monoxide and smoke alarms weekly. Keep a fire extinguisher and a fire blanket within reach of the galley and the stove, and never leave a solid fuel stove unattended with the vents wide open. Check the flue and chimney for tar, keep spare fuel dry and away from heat, and know where your fuel shut-off and battery isolators are in the dark.

Do that, and a frosty morning on the cut becomes something to look forward to — a hot mug of tea, a glowing stove and the canal quietly steaming either side of you.