Hello All,
 
Sorry for the regionality (?) of this question, but does anyone in the
mid-southern US use top ventilation in the winter?  What are the
benefits/drawbacks?  This finishes my second season on beekeeping, and I
have never ventilated on the top (eg Imrie Shim).  I anxiously await your
responses!
 
Steve Creasy in Maryville, Tennessee