I’m currently in the process of finishing my basement also. My question is about a door around the furnace. I have a gas FHA furnace and AC unit directly under my steps. I want to put bi-fold doors around the furnace and try to reduce the sound of the unit while it is running. It is not a loud unit. I was wondering if it would be acceptable to use a solid bi-fold door or use a louvered bi-fold door around the unit? Does a unit as such require a lot of ventilation? Any suggestions or recommendations?