I have been for a little while the proud owner of an Ecofan. A bit esoteric, I know, and not something my boatmen ancestors would have known about, or needed. They lived in a cabin about ten feet long. I know I am supposed to translate imperial to metric measures, but how many of you have metre-long feet?!
So, for those of you who are not boaters, what, exactly, is an Ecofan? Well, here is an image.

When the stove gets warm enough the fan starts spinning. After that it drives heat around the boat. Without the fan the heat from the stove simply rises and spreads along the top of the cabin. So, there you are, doing the crossword or watching telly, thinking it’s a bit chilly, and you stand up to find there is a sauna from shoulder height upwards. The fan spreads the heat more evenly.
The manufacturer claims the Ecofan will save up to 18% of fuel and, going on limited experience, that doesn’t seem extravagant. I don’t have a thermometer, yet, but with this light snow it’s not warming up outside, so any help is appreciated.
