We are currently going though a very cold winter here in Sweden – the coldest since I moved here in the early 90s. There is, however, enough sway in temperature to allow the slightly warmer, cloudy days that afford snow. A lot of snow. As it builds up outside, smothering our lawn (just got in from a major shoveling session) and stripping the street of any definition, it feels comforting to get inside and snuggle up next to our ‘kakelugn’.
I’ve heard ‘kakelugn’ translated as ‘tile stove’ or ‘contra-flow stove’ but recently I came across the name ‘masonry heater’ in a green building magazine. Being Australian I’d never seen nor heard of them before I came to Sweden, therefore I’ve never referred to them as anything other then ‘kakelungnar’. Though ‘masonry heater’ is a blanket name covering the many styles and variations that have popped up throughout the world, for the sake of simplifying things I’ve chosen to use it for this blog.
So what is it? The masonry heater is essentially a combustible stove built for slow heat release, thereby making it energy efficient and easy to manage. They are often large and heavy (some weighing up to 2 tons) and come in many designs (see picture of ours). The small firebox is found at the bottom centre and above that a network of channels run through and between masonry, like an elaborate maze. These channels are designed to retain the combustion gases from the fire for as long as possible. Around them material, such as soap stone, olivine, or, as in the older models, simple clay bricks, warm up and, due to the material’s unique thermal capabilities, stay warm for anything up to 24 hours. As ours is quite old and uses bricks for its heat retention, it doesn’t quite last as long as 24 hours, but I would say 18 hours is not unrealistic. The key thing to remember is how little wood one uses to heat it and how much energy one gains from it. Not to mention how little labour is involved.
Its origins: It would seem that the masonry heater dates back to the middle ages in Germany but it wasn’t until the 1700s that, due to concerns over the dwindling wood supplies in Sweden, two Swedes came up with the idea of the contra-flow system (particularly the down-draught contra flow). The architect Carl Johan Cronstedt and General Fabian Wrede presented the first models to the Swedish government in the 1730s and by the late 1700s Sweden had become famous for its cosy indoor temperatures.
Now and the future: Man’s evolution has been built on such monumental moments – responding to crisis and overcoming adversity. In a country as cold as this one energy will always be a major concern. Due to the inventiveness of a few individuals Sweden was able to tackle an 18th century energy efficiency crisis. Naturally we take our heating from elsewhere now (hydro, nuclear and biomass) but the masonry stove remains a desired commodity. Provided the wood is renewable, it remains an energy-efficient tool and could well regain prominence in a world increasingly concerned about the depletion of fossil fuels.
A final observation: Its fascinating how warm we generally are over here during the winter. It might be minus 10 outside but it's always 20 plus or more inside. In Australia, as a kid, I remember how cold I would get in Sydney around July – at home, particularly at night. Naturally, Aussies don’t really need central heating but I find it fascinating that I am generally warmer over here then I was in Australia during winter.
C
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