Why not switch to a lager yeast? These ferment at low temps, and perform at their best at 10-12 degC. I use these in Winter in Melbourne, and do not heat the brew at all. Temp falls to well below 10 degC overnight, and warms up to just under 20degC during the day. As there is a fair bit of thermal mass in the fermenter, the wort temp will range from approx 8 to 12 degC.
Saflager S23 is a great lager yeast. It ferments very cleanly, but can take 2-3 weeks to finish.
Give S23 a try and I think that you will be impressed.
Barry