100% year round garage brewer. Love not really having to deal with weather issues (rain, snow, wind, etc) except for heat/humidity in the summer and frigid temps in winter (Western NY south of Buffalo, Lake Erie). I have not had any issues with mold or moisture problems in my garage but I only brew 5 gallon batches at a time. Just leave the garage door about 1/3 open to allow for some airflow and CO escape from propane burning.
Having floor drains also is a real plus!