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Burning desire

Wood-burning stoves may be fashionable, but are they functional? Our undercover expert makes a cool assessment

November/December 2013

Ten years ago, wood-burning stoves were the preserve of eccentrics and eco-warriors—if you had any sense, under-floor heating was what you aspired to. All that started to change in the mid-2000s, when interiors magazines began using stoves in their photo shoots. Then in 2009 gas prices soared and suddenly heating was something people wanted to do themselves. The Guardian picked a wood-burning stove as one of the five best eco-products of the year. In the past 12 months, more than 200,000 new wood stoves were fitted in Britain alone.

But a stove is not something to buy on a whim. It needs either a chimney or a flue feeding to the outside, and if you're planning to put it in an alcove there are laws about how much space to leave around it. It may be efficient, but it will need feeding: few stoves can be left to their own devices for more than four hours without burning out. When it's working at full pelt, its cast-iron casings will get hot enough to boil a kettle on, so you'll have to keep children, pets and the wobbly-legged clear of it. And its chimney will need cleaning by a certificated sweep every year, and its ashpan by you pretty much every day—at least when you're using it.

Most modern wood-burning stoves have a heating efficiency—the measure of how much of the heat value in wood is delivered into a room—of around 75-85%, compared with 32% for an open fire. Much of the heat produced by an open fire goes up the chimney, whereas stoves use baffles to recirculate hot air around the inside of the firebox, and dampers that slow both the inward flow of cold air and the rate at which your wood burns. Yet the average, fireplace-set stove will still have an only modestly warm nominal heat output of 5kw. (Compare this with the 220kwh it takes to heat the average British house for one day in winter.) So if you want it as a main heat source, you'll have to go larger—though building regulations will then demand you have a permanently open air-vent punched into your wall. Whatever the size, you're going to need somewhere close to the stove to store a fair amount of wood. A 5kw-output model will use around half a cubic metre of logs—about three wheelbarrow-loads—to heat a single room for a week.

The look of the thing seems to make very little difference to efficiency: an ultra-modern cylinder or a traditional square box will do a similar job, and all stoves will have a window, a door, a flue and an ashpan. Large windows are lovely for fire-gazing, but have a tendency to gum up with resin and soot unless you rub the glass with yesterday's cold ash; those with an "airwash" system solve this problem by directing air across the glass, to keep flames and their carbon-load safely clear. Other, smaller design details can be telling. The Morsø 7448 (5.7kw, £1,800, above), a 21st-century cylinder with windows on two sides, is mounted on a pedestal, which means you don't have to bend down to feed it or empty the ashpan. The Stovax Riva Studio 1 (5kw, £1,300) is a modern, clean-lined box that can be mounted high on a bench for greater visual impact. The Jotul F400 (10.5kw, £1,550) is a quite different kettle of wood. It has a gothic-arched, airwashed glass door that is both wide enough to take 50cm logs, and has a removable handle—useful if you have inquisitive young children.

Lastly: fuel. Your wood has to be either kiln-dried, or seasoned—in other words, left to dry out naturally for up to two years after felling—otherwise the efficiency savings will disappear up the chimney along with the water vapour. Willow and pine are cheaper, but are all snap, crackle and fizzle-out; ash, holly and oak cost more, but burn long, hot and strong. Just how we like it.

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