contraptionated
New Member
Is it possible for you to drop the ceiling (by framing and foam board construction) and put a nice rectangular exhaust port over each fixture through the ceiling?The room above the drop ceiling can contain exhaust fans horizontally mounted and vented straight out a window. If you dramatically increase the size of the exhaust duct and eliminate bends and flex duct you will get more airflow. The ducting can easily be made from the exact same foam board in your room. Also, with no physical connection between the exhaust ports above the lights and the exhaust fan in the room above the grow room you will eliminate all the friction losses that prevent your fans from sucking out the max rated cfm.At best, you are only exhausting 1/3 of the rated cfm of your fans by using flex duct. On top of that you also have some bends in your ducting which reduce output considerably more.Venting out of an open window (clandestinely) takes some skill but its done rather easily from second story (or further up ). I cannot ever tell you how to make a full window size exterior exhaust outlet (trade secret , sorry)but with a little imagination you could figure it out.
By constructing oversized runs of rectangular foamboard duct (lining the interior of the duct with steel mesh fabric and fiberglass insulation) and sizing the duct to a full window glass (about 24" x 27" or a little more or less) you will be able to exhaust the max cfm rating of your fan/filter combos and not much airflow will be detected going through the glass less window pane . With a little imagination you could figure out how to make it look like a regular closed window.
I've exhausted 3600 watt rooms (72 sq. ft with 6'7" ceiling) to acceptable levels in the middle of Summer with no help from AC units. Just 2 - 10" fan/filter combos . What matters most is the direction of air flow in and out of the room and large straight ducts.The best airflow you could ever achieve is bottom to top. Up through a foam board perforated raised floor diffuser (for equitable distribution of intake air) and out of many oversized exhaust ports located directly above each heat source. That cannot be argued. That is an infallible scientific fact. You basically want to make your room similar to a large vertical piece of rectangular duct with the air flowing upward. Only this duct happens to contain a grow room.
By constructing oversized runs of rectangular foamboard duct (lining the interior of the duct with steel mesh fabric and fiberglass insulation) and sizing the duct to a full window glass (about 24" x 27" or a little more or less) you will be able to exhaust the max cfm rating of your fan/filter combos and not much airflow will be detected going through the glass less window pane . With a little imagination you could figure out how to make it look like a regular closed window.
I've exhausted 3600 watt rooms (72 sq. ft with 6'7" ceiling) to acceptable levels in the middle of Summer with no help from AC units. Just 2 - 10" fan/filter combos . What matters most is the direction of air flow in and out of the room and large straight ducts.The best airflow you could ever achieve is bottom to top. Up through a foam board perforated raised floor diffuser (for equitable distribution of intake air) and out of many oversized exhaust ports located directly above each heat source. That cannot be argued. That is an infallible scientific fact. You basically want to make your room similar to a large vertical piece of rectangular duct with the air flowing upward. Only this duct happens to contain a grow room.