Attic fan for Ventilation...Could this work?

turtledove53 · #1 2010-01-31, 9:10pm

I posted this in the Tips section...but it probably should be here instead.

Would this attic fan work if ducted straight to the top of a hood?

Master Flow Power Roof Mount Vent 1600 CFM'S $118.00

http://www.homedepot.com/webapp/wcs/...ctId=100072633

I don't have anything set up for ventilation yet. Currently work in my shop that has a lot of air flow in it, but I would like to bring my studio set up into the small 2nd bedroom of my mobile home.

I was thinking that I could put this on the roof with galvanized ducting going straight up from a hood over my work bench.

What do you all think?

NMLinda · #2 2010-02-01, 10:39pm

Unfortunately, the link seems to be broken, so it's hard to comment. Do you have an updated one?

Linda

turtledove53 · #3 2010-02-04, 11:54am

Quote:

Originally Posted by NMLinda

Unfortunately, the link seems to be broken, so it's hard to comment. Do you have an updated one?

Linda

I will include picture and description here since the link is not reliable. The proposed installation is in a mobile home that does not have an attic...this would went just from the hood.

Master Flow Power Roof Mount Vent 1600 CFM'S (Shingle Match Weatherwood)
Model # PR3DXSMWW Internet/Catalog # 100072633

Our Power Roof Vents are your best overall investment in attic ventilation. Our vents mover the greatest volume of hot and/or humid air from your attic, saving you more in heating and cooling costs than any other type of ventilation. Available in popular colors to blend with your roof.

Reduces Energy Costs and saves money
Mounts on the back of your roof
Blows hot air out side and cools the attic
Helps prolong life of the roof and Shingles
MFG Brand Name : Master Flow
MFG Model # : PR3DXSMWW
MFG Part # : PR3DXSMWW

NMLinda · #4 2010-02-05, 11:49am

Thanks for posting the info. With such a short run straight up through the roof, no bends, I don't see why it wouldn't work

Linda

turtledove53 · #5 2010-02-05, 12:01pm

Thanks Linda.

Moth · #6 2010-02-16, 9:43am

I use almost this exact same fan...mine is only 1200 cfms...but otherwise the same.

This baby sucks air. It works great...but make sure you have enough make-up air coming in. I just open the window behind me full open and if I stand under my vent hood, it will suck my hair up the vent. Sometimes I wish I had put it on a dimmer switch so I could turn it down.

Also, I installed mine on a box outside my basement window, then ran my ductwork through the box, into my vent...it's a run of about 4 feet total with no right angles--just one sloping upward curve.

When ice fell off my house roof- it hit my fan and killed it. So watch where and how you install this. I'm sorry I put mine under the eaves of the house. LOL

~~Mary

Moth · #7 2010-02-16, 9:45am

OH, and watch what comes with yours. Sometimes they come with a thermostat attached that controls the operation of the fan. Mine came with one. I took that off, and hardwired right into the fan motor with an on/off switch at my bench.

turtledove53 · #8 2010-02-17, 12:57am

Wow! Thanks so much Mary! Would you have gotten a lower CFM fan if you were doing it over again?

Moth · #9 2010-02-17, 10:10am

Not necessarily, Annie. I REALLY like knowing that I can fume and work with enamels (wearing a respirator) and I'm not going to kill myself with my craft. LOL

The only reason I wish I had put it on a dimmer is because in the winter time, it gets cold because this fan draws a lot of air and I don't necessarily always need 1200 cfm of air movement.

You also have to figure (read guesstimate) that you don't really get the full 1200 cfm that the fan is rated. You lose a little bit when you have bends in the pipe. You lose a little bit with turbulence inside the ducting. You lose a little bit when your fan cover gets snowy (or it's windy) or whatever. Even with a 1200 cfm fan I bet I'm only really moving about 800-900 cfm.

I'm glad I have the bigger fan, but a high/low setting or a dimmer would be nice to slow down the air exchange when I'm freezing and only working with regular glass. Then I could kick it up in the summer or if I'm working with metals or enamels.

Just something to think about. When I replace this fan, I'm replacing it with exactly the same thing---so that would illustrate my opinion best.

Have fun.
~~Mary

NMLinda · #10 2010-02-17, 5:53pm

Below is one of the best resources I know of to calculate what cfm your fan needs to be:

http://mikeaurelius.wordpress.com/ventilation-primer/

As Mary points out, you lose cfm to static pressure losses in vent ducting and bends, although you don't have any bends and very little ducting in your case

It's not generally a good idea to use a variable speed control if the cfm of your fan is already where this link calculates it should be for the vent hood you have. Also be aware that a fan's cfm isn't necessarily linear with the variable speed control setting. Unless the fan comes with some kind of information to that effect, you won't really know what protection level you actually have if you turn it down. You could accidentally put yourself in a situation where you've turned it down too far and you don't have enough draw.

Linda

Moth · #11 2010-02-18, 9:26am

That's an excellent point, Linda. One I didn't think of because I never actually put the dimmer on. LOL

Annie, whatever system you do end up with, be sure to do tests on it to make sure it is adequate. There are lots of threads on how to do those tests here in the safety forum.

~~Mary

pablordstribe · #12 2011-03-31, 6:38am

try this...

Powered Attic Ventilators

Mounts easily between rafters ? template included for cutting roof boards and shingles; Mesh screen keeps out birds and insects; 14 in. diameter steel blade specially designed for maximum air movement., Operates automatically. Adjustable thermostat built-in. http://www.thehardwarecity.com/produ...ilator/0002862

cheng076 · #13 2011-03-31, 10:12am

pablordstribe,
Note that she is in a mobile home...no rafters.

I think it will work just fine, IMHO
PJH

Cherylka · #14 2012-02-24, 8:30pm

Pardon me if this is obvious, but how would I connect the Attic Ventilator shown here to my fume hood? I looks like they just open into the attic, do thay have a flange or some such to connect to a duct?

I just started designing my ventilation system, using great advice on these boards, when I found out I need a new roof. So, I want to have the roofers install either a vent cap or maybe one of these while they're up there. Then I can connect to my hood down below.

Thanks!
Cheryl

cheng076 · #15 2012-02-25, 10:35am

If it does not have a duct flange built in then you can add one by inserting the flange underneath the fan flange when you install it or mount it in a box as Mary did.
PJH