I don't think any yeasts ferment below 40. You could get a keg bucket and a fishtank heater for very little outlay, you'd have a fantastic fermentation control system in that cold garage this way.
You pretty much need to have some heater / temp control, you don't want to freeze your beer when lagering it, if it drops into the twenties or below this could occur.
Give a man a beer, waste an hour. Teach a man to brew, and waste a lifetime! Bill Owen quote
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