garage ventalation

[red caddy]

My new shop is 35'x 60'X 13' wall height, total volume of about 40,000 cubic feet. the walls are block, and the roof is steel over 5/8 ths sheathing. insulated,with a radiant barrier, without a ridge vent. I have planned for a 4'X4' opening, centered in each eave end, 14' from the floor, for a louvered exhuast fan.
My question is, what is the formula for sizing fans (in CFM) for each opening, for proper air change ? I will be welding , fabricating and assembling, in the shop, but no painting (other than rattle cans) and all my machine tools will be under air, in a clean room. my main concern is to keep the "feels like" temp in the shop around 80 deg. with lots of fresh air, not easy to do in south florida. (average daytime air temp is 86 deg. with 80 % huMUDity) any ideas????? thanks, RED.

 

[Luckydevil]

try this... http://www.csgnetwork.com/airexchangecalc.html

Keep in mind that a large fan that you can point at yourself helps a lot also.

 

[red caddy]

fans

Luke, thanks for the fast reply. that is a very useful link, many good programs.
I currently have 5 -30 in. stand fans, that I use in my current shop,(2- 14' X 22' rented storage bays) but, I have to turn them off when I weld, or the quality of my welds (TIG/MIG) suffer. I've had to do most of my welding at night because of the heat in the shop with the door closed in the daytime.
My goal in the new shop, is to remove the heat from the top of the shop, without making it a wind tunnel, that I can't weld in. Most weld shops around here just live with the sweat, and weld behind/inside roll around flash curtins. The stuff I work on must meet both visual and NDT inspection standards for CrMO and aluminum seamless DOM tubing, so I can't compromise weld quality. There must be a way to ventalate my shop, and still maintain the weld quality, I just havent found it yet, any ideas? thanks, RED

 

[Kevin54]

T remove the heat from the top you need cross ventilation at the top. Just remember..Air out = air in. If you vent at the top with a fan, put a louver that you can open and close at the top opposite end. Without seeing a setup of your garage and not knowing whether you have a ceiling and/or insulation it is hard to really tell you how to do it. If you do have ceilings then a vent fan to pull at one end and a louver at the other wo let air in will cool it. Just make sure you size it larger than what the square footage calls out for by the Mfg. If you have an 85 deg. day and sun bearing down full bore, the attic temps are well above 140 degs. If you have no ceiling then try to size the fan and louvers with the fan oversized, a larger opening louver at the top, and a smaller opening at the bottom to draw. With doors and windows open would accomplish this, but what you want to avoid is air movement across your work. But the best bet would be ceiling insulation, vent fan and opposite louver in attic and air conditioning below. And attic insulation being no less than R-30. Heat is not so much the problem as the humidity. Remove the humidity and higher temps are comfortable. And about the only way to remove the humidity is with an air conditioner. Even a window AC will help drastically if everything is properly insulated.

Kevin