We had some really cold temperatures here last winter. My garage isn't heated and only one wall is really insulated.
Nothing froze at all. Compressor rarely ran though.
I know we had sub-zero windchills, but if you're further north you'd probably have issues.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10