I use my garage for lagering. I live in a cold winter climate, so I use a wrap type heater and digital temp controller to keep above freezing. A blanket goes over the fermenter (to help maintain a constant temp and to keep out any ambient natural light). I duct tape the temp probe to the side of the vessel, sometimes insulating it with a wad over kitchen towel over it. Temp set to, say anywhere from 33°F to 40°F, depending on the brew, with an offset of 2F°. Works really well.
The Ranco ETC 111000 digital temperature controller can be had off eBay for around $50. The wrap heater I have costs around $30 from a HBS. The only other thing needed is a cheap short power cord that gets cut in two and installed in the ETC ($5)..... and some duct tape! Probably one of the best pieces of equipment I have. Use it for ales in the basement too, to maintain higher temps.