Ventilators/fans question
 

Hi everyone

I´ve seen a variety of different types of fans with the same cfm but at very different prices. Usually inline fans are the most expensive while attic vents gable fans and simple exhaust fans are cheaper. So, if the cfm is enough, does it matter what type of fan I´m using? or do attic fans push instead of pulling air?

Thanks.

I cannot claim to be an expert, but for what it's worth:

I thought attic fans pulled out, but they are pulling the air up into your face. I always thought you wanted to draw it away from you and out.

The makeup air is really important, so figure out how it can come in and past you to vent the fumes away and out.

Most fan cfm numbers are totally bogus.

Until you get up into the 2000 cfm range (and the associated big $$$) most of the numbers listed for a ventilation fan are pretty much twice or three times what they actually deliver if that.

I used the fan from my old house furnace rated for 100,000 btu for my 2100 square foot, 150 year old house.
It's a squirrel cage fan about a foot across and I am not real certain that it moves air fast enough or with the volume as I would prefer unless I decide to enclose the back and sides.

A fan specification almost as important as CFM is SP: Static Pressure https://www.dscr.com/blog/static-pressure-important/
A simple box fan on the floor might have high CFM but if mounted in a window and wind is blowing against that side of the building, the CFM might be nil.

A good quality fan will have a published CFM vs SP table or graph. I'd say the layout of your studio determines the design of fan to buy. If you need to go through ductwork, get an inline fan (although I haven't found any with metal (not plastic) impellers). The squirrel cage fans are typically better at blowing than sucking (although they can work well enough).

Myself, I bought a 1/4 HP commercial duty direct drive propeller fan to go in the window of my basement garage. I will be making a hood over the work bench to direct fumes to the fan. HVACquick.com is great to work with. Canarm sent me a previously returned fan and did not bother to properly repackage it for shipping. HVACquick gave me a generous partial refund for the bent corner that resulted.

Have been using a Soler & Palau T-250 Fan which fits 10 inch round duct in combination with a barley box. All installed in 2012 and is still performing well and without issues.

Folks are correct in that SP is a major factor in air flow. One must take into account, run length, number and type of elbows, etc to determine the overall CFM. And as pointed out, a window box fan is not an acceptable option for the lampworker.