I have 4 on my roof. they circulate the air. in the summer, they can cool a little bit. save some money. but in the winter they can cool a little bit too. waste some money. so if you live in northern part, you definitely don't need to have it installed. don't know how to install them.
【在 G***G 的大作中提到】 : I have 4 on my roof. they circulate the air. : in the summer, they can cool a little bit. save some money. : but in the winter they can cool a little bit too. waste some money. : so if you live in northern part, you definitely don't need to have it : installed. : don't know how to install them.