Yet another ventilation question-newbie

[AmandaL]

My studio will be in a room we are converting to a sunroom. The room is 8x24 and I will have use of 1/2 of it with windows in front,to the side and all along 8 ft behind me...

I have a carlisle mini cc and plan to use nat gas and a concentrator.

There is a crawl space w/ basement windows beneath this room.

My husband and I have been reading all of the many ventilation threads on here-all of which are pretty much shooting down his ideas. (he was thinking about making something like GLasscraft has that would be on the bench top or was thinking of hooking up thru a dust collector and exausting it outside)...It's really just confusing me teh more I read...

The idea we discussed a bit ago was to use some sort of range hood, galvanized 2x8 flat ductwork between the 2x4's to the crawlspace then vented out a basement window which would be behind me but nearly 20 ft to my left so it shouldn't effect the fresh air intake. Now my question is how do i figure how large to make the hood-or can I use a regular hood and rig it to make it larger? DH asked about using something from Fantech or a squirrel cage fan and have that hooked up in the crawlspace that way it's not so loud in the studio. Is there somewhere to calculate what cfm's I need (does my square footage dictate that at all?)

Any thoughts/opinions? I need all the help I can get!!!Thanks!!!
Amanda

[Dale M.]

You are trying to hard to reinvent ventilation....

Use the KISS principle (Keep It Simple Stupid)...

Hood over bench, attached to a squirrel cage fan, run duct out side....

Have sufficient make up air source coming in behind you.....

Basic formula is hood opening in square feet multiplied by 100 equals fan size in cubic feet a minute (cfm)...

Your 2x8 inch duct is only 16 square inches of "duct area", way to small! Where a 8 inch round duct has a "duct area" of 50.26 square inches... About minimum duct size for good ventilation... IF duct is to small, there is to much static pressure, this restricts air flow, restricted air flow means reduce efficiency...

Squirrel cage blowers of almost any size are available form places like Graingers, McMaster-Carr and maybe even local HVAC shop or salvage yard...

Ventilation Basics (http://www.artglassanswers.com/forum/viewtopic.php?t=150)

Dale

[MikeAurelius]

Amanda - you mention the room has lots of windows. If they are double hung windows, remove the screen, have your DH make a plywood insert to fit into the window opening, and mount the exhaust ducting to the plywood insert. Keep the run as short as possible, use smooth sided galvanized metal hvac ducting, and use as few as possible bends in the run. Use a window that is near your bench.

If your bench is on the outside wall, use a similar method to bring in fresh air. Just be sure the exhaust and fresh air intake are at least 10 linear feet apart. The fresh air can be ducted to underneath the bench, then ducted up into the bench area with a standard floor vent.

For an overhead vent hood, I like to see a minimum of 125 CFM per square foot of coverage - overhead vent hoods pull a lot of non-contaminated room air, and the additional CFM makes sure that you have good "pull" at the bench surface where the torch is.

If you decide to use a totally enclosed hood style (5 sided box - left, right, back, top) that mounts directly to the bench, you can use 80 to 100 CFM per square foot.

You can find basic match for calculating static pressures and design information here:

http://www.artglassforum.com/forums/showthread.php?t=2293
http://www.artglassforum.com/forums/showthread.php?t=2294