Originally Posted by wormraper
try wrapping your carboy in a blanket as an insulation layer. put it in the warmest spot in the house, say the laundry closet or something.
Yup this is usually enough. If not you can go to the next level and wire up a 25 dollar ebay temp controller and hook up a heat belt, ceramic heater or an older analog electric blanket without any safety shutoof.
This is a homebrewing heat belt available online or at every LHBS.
This is the ubiquitous Ebay temp controller wired up with several different sockets, there's only about 100,000 threads and wiring diagrams on here to help folks, including mine,
You can even but it all into a light blocking chamber made from a rubbermade bin, and even use it to lager on a sunporch or in a garage if you live in a cold clime for any part of the year...
You just pretty much tape the temp probe to the side of your fermenter, and when it drops below your set temp the heater will come on, and stay on as long as it needs.