Mandaloril,
I am not sure of the climatic conditions of where you are situated, but i find it very difficult to maintain a low temp for fermentation of lagers without some cooling. living in Qld i use a fridge to ferment my lagers even in the middle of winter as we don't really experience a cold winter. having said that i have also used an insulated wooden box and frozen pet soft drink bottles of ice to keep the temps down. The box is made of plywood and insulated with styrofoam. with a little bit of trial and error you can control the temps reasonably well. i use about 6 1.25lt bottles and change them daily. this allows me to maintain a temp of approx 12 to 15 degrees C. I use this as a backup when I cannot use my fridge to ferment. I also find it useful to keep ale fermentation under 20 degrees C in the middle of summer.
hope this helps
cheers