SIAP, you could use a lager (bottom fermenting) yeast instead of ale or bread yeast.
It is used to produce lager beer (most German beers, most common American beers [bud, miller, coors, etc.]) and is meant for colder fermentation temperatures.
Just a thought. Also, if you insulate the fermenter, the fermentation process itself will keep the liquid a little warmer than the ambient air temperature.