Are the shutters on the SD24 line of fans sealed good? I am looking something to use in a cold climate & do not want un-necessary air drafting in when not in use.

The SD24 fan uses a tightly closing, gravity-assisted aluminum shutter system designed to minimize backdrafts when the fan is not in use. While the shutters are not completely air-tight like an insulated damper, they close securely and significantly reduce cold air infiltration and drafts. For very cold climates, many customers pair the fan with an insulated backdraft damper for added protection. This shutter design from Canarm is well-suited for cold-weather applications where limiting unwanted airflow is important.