Hey Daduck, thanks for swapping goods here. It is very informative to hear how others are working through their issues.

I have the luxury of time. I'm itching to get started but I have a huge project list that I have to work through before I can start the room. Yesterday I put down 550 sf of sod in the rain... So I have had all kinds of time for planning and research. This a good thing. I received some good advice early on to settle on a plan and work with it, rather than getting bogged down with endless configuration changes. However, it took me a while to understand my space needs. During research I concluded that I need a clone / veg / mother chamber. I will also need for space to work around the plants. I will also want some floor space for buckets, accessories, etc. plus shelving for nutes, tools, and miscellaneous items. I doubled the room size to account for these realizations.

I will be doing relatively small grows - 4 to 8 plants and I will do them scrog style to maximize both space and light. I am lucky that I have a nice unfinished space to work with, venting issues aside. I will section off 1/3 of the room with wood frame and drywall. (Note if you are building from scratch, apply liberal bead of silicone to the studs and joists before you hang your drywall. This is one of he most effective means of mitigating noise that you can employ).

My room will be 8'.5"L x 6'W x 6'.5"H for 332 cubic feet. I will be pulling fresh air from an adjacent room and venting into a third room. I am not concerned about the door. The current space is already light tight before I even start. I will seal it no worries and the rest of the room will be sealed tight by drywall. Once the room has a reasonably good seal an appropriately sized fan will create enough negative pressure so that the only air escaping the room is through the vent. My duct setup is very simple. Only a few feet long with no elbows or obstructions to account for besides the filter. I will use ona in the vent room too.

The key factor here is employing a good appropriately sized fan and a very good filter. So if I want to exchange the air every 5 minutes my calculation looks like this:

332 CF / 5 = 66.5 CFM
66.5 x .5 (to account for 5 feet of duct) = 99.7 CFM
99.7 x 1.3 (to account for filter) = 129.6 CFM

I ran this for exchanging air every 4 minutes although with my setup 5 minutes should be sufficient.

332 CF / 4 = 83 CFM
83 x .5 (to account for 5 feet of duct) = 124.5 CFM
124.5 x 1.3 (to account for filter) = 168.9 CFM

If you are looking for help with your calculations checkout Rhizome's Noob Guide. It is an outstanding read if you haven't seen it:

http://boards.cannabis.com/indoor-gr...-progress.html See the second post which deals with ventilation.