--- title: Why is it necessary to cut the joists when installing Belt-Drive Whole House Fans? description: Here is some information explaining why it's necessary to cut the joists when installing the belt-drive whole house fan. --- [Skip to content](https://help.gibraltarbuildingproducts.com/en/knowledge/why-is-it-necessary-to-cut-the-joists-when-installing-belt-drive-whole-house-fans#main-content) English Show submenu for translations ![GBAD Full Color.png](https://blog.stealthbond.com/hubfs/GBAD%20Full%20Color.png) Open main navigation Close main navigation - English Show submenu for translations - Go to www.gibraltarbuildingproducts.com Go to www.gibraltarbuildingproducts.com Hello. How can we help you? - There are no suggestions because the search field is empty. 1. [Help Center](https://help.gibraltarbuildingproducts.com/en/knowledge?hsLang=en) 2. [Ventilation](https://help.gibraltarbuildingproducts.com/en/knowledge/ventilation?hsLang=en) 3. [Whole House Fan](https://help.gibraltarbuildingproducts.com/en/knowledge/ventilation?hsLang=en#whole-house-fan) # Why is it necessary to cut the joists when installing Belt-Drive Whole House Fans? ## Here is some information explaining why it's necessary to cut the joists when installing the belt-drive whole house fan. The reason the belt-drive installation requires the cutting of joists is the Air Vent shutter specific for that unit. Air Vent belt-drive motors require that the shutter vanes all open and that the vanes be directed/oriented in such a way as to direct airflow to the motor (to help keep the motor cool and prevent overheating). The shutter vanes cannot fully open unless the joist is cut because the joist will be in the way of some of the vanes. 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