# Looking for a square (16" O/C) carbon filter exhaust fan



## Hackerman (Apr 26, 2014)

I would like to simply mount an exhaust fan in the ceiling of my grow room. It's standard 16" O/C wood construction.

I picture a high volume bathroom style exhaust fan with a carbon filter all built in. I saw a Broan model that had a charcoal filter but I doubt that is the same.

I am using a hood (not air cooled) so I figure I'll just vent the heat right through the ceiling and into the rafters above. That would stink up the room above pretty bad so I figure a carbon filter built in would do the trick.

I did some searching and I didn't find anything resembling what I have in mind. Would probably be a pretty simple DIY project but if I could get one that's well designed and well made (with easily replaceable filters), it would probably be better.

Anyone ever hear of anything like this?

Thanks


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## Hackerman (Apr 27, 2014)

Another related question. On the canister style filters like the Phresh and the others, does it matter which direction the air flows through? 

If not, I assume it could be mounted on either side of the fan and the fan could suck the air through the filter or blow it through.

EDIT: From my reading, you suck the air through the filter. Thanks


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## lyfespan (Apr 27, 2014)

First off what size is the room you're going to be venting? Average fart fan, is 110 cfm' and already costs more than one of these setups

[ame]http://www.amazon.com/VenTech-Hydroponic-Inline-Carbon-Control/dp/B0051HDECS/ref=pd_sim_lg_9?ie=UTF8&refRID=0X0HXPEMT5KJCX27CSDX[/ame]


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## Hackerman (Apr 27, 2014)

The room is 4' x 7'. Yeah, I have been reading and learning. Now, it's down to which canister filter to buy. Phresh looks like it gets good reviews. And something Mountain.

It looks like a Phresh 6x16 with my Active Air 400 CFM fan will be a good choice. However, I was looking for something that would mount nicely in the ceiling between the rafters. Mounting this giant Active Air fan doesn't look like it's too easy.


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## lyfespan (Apr 27, 2014)

Hackerman said:


> The room is 4' x 7'. Yeah, I have been reading and learning. Now, it's down to which canister filter to buy. Phresh looks like it gets good reviews. And something Mountain.
> 
> It looks like a Phresh 6x16 with my Active Air 400 CFM fan will be a good choice. However, I was looking for something that would mount nicely in the ceiling between the rafters. Mounting this giant Active Air fan doesn't look like it's too easy.



Mount the fan in the attic, prep the fan down stairs, by screwing 2  2x4s that are longer than 16 inches to the fan assembly. Poke a long skinny screwdriver Thursday the ceiling about where you want the fan, if it keeps slipping out tape it up there. Now go up in the attic, find the driver, and see how close to where you need to mount the fan, make necessary adjustments. Set the fan a crossed the rafters, you might want to put isolators under the 2x4s to dampen sound, you can screw it down if you want. Now go back into the room and using a hole saw or key whole saw cut your small circle out of the ceiling push tubing up to fan body and connect, presto clean instillation and less noise.


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## Hackerman (Apr 27, 2014)

Unfortunately, I don't have an attic on top of me. Just the finished floor from the room above. So, I only have 16" of vertical space. I almost have to mount the fan between the rafters at the ceiling level so I have enough room above for the fan outlet and the duct. I am already going 90 degrees right out of the fan, which isn't great but I have limited options here.

I originally was going to use duct and put the fan in the next room but I have a circuit run just for my room and I want to keep everything on that circuit. So, to avoid having to run extension cords all over, I want to keep the fan, ballast and all the other stuff for this room plugged into the same outlet.

Push come to shove, I'll build a shelf in the room and set the fan on it and then use duct to do whatever I need to do. Not the end of the world but I like things nice and neat. LOL


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## Hackerman (Apr 27, 2014)

I will probably be mounting the fan to the rafters in one way or another. What are the best insulators to use to cut down vibration noise.


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## The Hemp Goddess (Apr 27, 2014)

IMO, it is a bad idea to vent a grow room into the space between floors.  You are venting warm moist air into a space with no where for it to go.  There is a reason that dryer venting and bathroom exhaust fans are always run to the outside...mold.  You do not want to take a chance of mold growing between the floors.  Also are you sure you have 16" between the floors.  I am a (retiring) plumber and I plumbed a whole lot of multi story new homes in my day.  I don't remember any having that much space between floors--we were lucky to have a foot.  Mold is your real danger--you have no where for this warm moist air to go.  You really cannot exhaust into another enclosed space. unless THAT space can be exhausted.  Even a space as large as an attic presents mold potential and ducting should always be run to a gable end where it can escape.


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## Hackerman (Apr 27, 2014)

Hmmmmm? That presents a whole new group of problems. LOL

Never really thought about it. Always figured there was more than enough space for everything to dissipate. Been doing it since I bought this house in '85. I may take a flashlight and look to see if I have any mold problems.

And, you are right. The rafters are probably 2x12, not 2x16. Guess I was confused with the 16 o/c number.

I may be able to run a duct to the furnace flue but it would be a 50" run from the fan to the furnace. Is that OK?


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## lyfespan (Apr 27, 2014)

The Hemp Goddess said:


> IMO, it is a bad idea to vent a grow room into the space between floors.  You are venting warm moist air into a space with no where for it to go.  There is a reason that dryer venting and bathroom exhaust fans are always run to the outside...mold.  You do not want to take a chance of mold growing between the floors.  Also are you sure you have 16" between the floors.  I am a (retiring) plumber and I plumbed a whole lot of multi story new homes in my day.  I don't remember any having that much space between floors--we were lucky to have a foot.  Mold is your real danger--you have no where for this warm moist air to go.  You really cannot exhaust into another enclosed space. unless THAT space can be exhausted.  Even a space as large as an attic presents mold potential and ducting should always be run to a gable end where it can escape.


Venting is area specific, here in SoCal I would never fear mold from venting into my attic, but I would never vent into the dead space between floors, unless I cut a vent thru the stucco to the outside.

And yes there are no 2x16 floor joists lol, just tight cramped spaces.


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## lyfespan (Apr 27, 2014)

Hackerman said:


> Hmmmmm? That presents a whole new group of problems. LOL
> 
> Never really thought about it. Always figured there was more than enough space for everything to dissipate. Been doing it since I bought this house in '85. I may take a flashlight and look to see if I have any mold problems.
> 
> ...


You could do that just tie into the furnace venting, and I hope you do mean 50 inches and not feet. Pictures could help us help ya out a lil easier too.


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## Hackerman (Apr 27, 2014)

No, it's a 40 to 50 foot run.


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## The Hemp Goddess (Apr 27, 2014)

Natural gas and propane furnaces exhaust dangerous gases.  I would be concerned that the exhaust fan might push these back into your living spaces.  

You are right about specific conditions.  I also do not worry about venting into the crawl space or attic space as my climate rivals the saraha desert for low humidity.  Hackman on the other hand has mentioned in other posts his concern about the high humidity in his space.

Hackman, the space you are venting into is not the entire space between the floors--it is just a joist bay.  The floor and ceiling are separated by either engineered trusses that are solid or 2 x 12s that are also solid.  Every so often there will be places where there are supports between the floor joists.  So you are looking at a space if typical is about 12" high, 16" wide and maybe 12' long....16 sq ft.  You are pushing air into a contained space.  When the air has no place to go (compresses as much as it can, the fan will start working harder to try and push air into a space that is already full.  When the compressed air reaches the capacity of the fan to blow, it ceases exhausting air.


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## Hackerman (Apr 27, 2014)

I just took another look and it's strange. This area where my room in has a lowered ceiling. So, I actually have a 12"  vertical space that covers about 10 joists. Then, there is a lowered area that looks like it was designed to run the cold air return but it's all open all the way to the furnace room. It's a little hard to explain. I'll take a picture. It's looks like I'm venting to the entire underside of the house. I need to take a better look and a few pics.


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## The Hemp Goddess (Apr 28, 2014)

They could have a lowered space for air return, but it is only going to be so open--you simply cannot run flooring without joists and they usually only drop the ceiling enough to accommodate the size of the ducting.  I have probably plumbed a thousand new residences in my years as a plumber and it is exceedingly rare to have a space like you describe.  Things like that are usually only built by people who do their own building, plumbing, or HVAC work because they do not know how to deal with things like 3" drainage lines and air returns or ducting.  Plumbers would love it--drilling all those joists to accommodated 3" drainage lines is not fun.


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## Hackerman (Apr 28, 2014)

OK, I took a good look at this today. And, I am pretty happy with what I saw.

There is a raceway 6' wide and about 12" deep that runs the length of the house. It is almost empty (except for a few water lines) and a couple ducts are using it way on the other end of the house near the furnace. 

My room is right below the raceway so I am venting into that. Since the raceway runs the length of the house, I am literally ducting into the entire underside of the house. And, like I said, other than those few ducts at the other end of the house and a couple water pipes, this is all wide open.

I don't think I have to worry about anything. What do you all think?


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## Hushpuppy (Apr 28, 2014)

I have an idea maybe. If there is a problem exhausting through the ceiling, what about exhausting through the floor of the grow space. Mount the filter to the ceiling where it will pick up the warmest, stale air then run flex hose from it, down through the floor where the fan is mounted so that it pulls the air out and exhausts under the house. You can pull air from a fairly long distance if there isn't any resistance on the air flow. I was pulling air about 12' from my tents, plus another 3-4' within the tent to the filter. I would also recommend that you get as big a filter as you can afford because the bigger they are the longer they will last before having to be replaced.


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## Hackerman (Apr 28, 2014)

Concrete below me.  I'm in the basement.

I plan to get the Phresh 6" x 16". I thought about the 6 x 24 but that takes a lot of space. I still might. Depends on what's at the store tomorrow.


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## Hackerman (May 4, 2014)

I have this mostly setup and I am tweaking everything.

Instead of venting into the joist area and the raceway, I am going to run a flex duck (or I could go rigid if it offered any advantage) from the fan output, down the raceway to a room nearby but separate. The run will be about 25 feet.

Since that is kind of a long run, I was thinking about using a 6" to 8" adapter after the fan and use an 8" flex duct for the run instead of a 6". I have read some bad things about using reducers with fans but I think the way I am planning is OK.

Would it be better just to stay with 6" or am I OK with sizing up to 8" with a reducer?


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## The Hemp Goddess (May 4, 2014)

I don't see any advantage to going from a 6" to an 8".  If anything, I would think it would be detrimental, not beneficial.  Since you are running that far, make sure you have no sags and dipsy-doodles and make as few runs as possible.  It is more the sags and corners that cause the fan to lose cfms, a 25' straight run with no sags I think you will be fine.  In fact a lot better than a shorter run with a lots of turns or sags.  Ducting with a smooth inner wall will present less resistance than something ribbed like dryer ducting.


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## lyfespan (May 4, 2014)

Hackerman said:


> I have this mostly setup and I am tweaking everything.
> 
> Instead of venting into the joist area and the raceway, I am going to run a flex duck (or I could go rigid if it offered any advantage) from the fan output, down the raceway to a room nearby but separate. The run will be about 25 feet.
> 
> ...



I will talk with my neighbor, he's and heating and air engineer, but I believe that the theory is, that if you are going to have a long run for intake or exhaust, you need to start large and taper down to the size you need. This is again to cut down on static resistance. I should be seeming him tomorrow morning, and will have all your answers.


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## Hackerman (May 4, 2014)

My thinking behind going to an 8" was that the air could almost "dump" into the 8" from the 6", thus relieving any potential for back pressure in a 25' run. No?

It's a straight run, pretty much. And since the flex duct comes in 25' lengths, it would be stretched pretty tight. Even stretched tight, there are plenty of ridges in flex duct.

Still, if you think a rigid duct would be better than the flex stuff they have 8' x 6" rigid duct at the store pretty cheap..... it only costs a little more to go first class. LOL

Thanks, LS


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## lyfespan (May 4, 2014)

I also would like to inquire about the distance of the fan blades from the cylinder body of the fan. Is about a 1/2 in, if so you have an opportunity to improve and quiet the fan with some spray adhesive and thin foam insulation. Just remove the blade assembly spray the body and sleeve it with the foam, this will make it quieter and improve air moving. I'm going to look for some air flow diagrams that will help people with these air moving issues.

Just remember good rule of thumb is to intake cold clean air and bring it into the room at the lowest point possible, and to keep the exhaust pick up as far away from the return(intake entry) and as high up as you can, heat rises as we all know.


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## The Hemp Goddess (May 4, 2014)

You cannot insulate this kind of fan in that manner..  However, you can make an insulated box to put it in if noise is a problem.  We had a DIY here somewhere at one time....  

I don't think you are going to have back pressure problems unless you have a lot of sags or turns--straight runs with no bends makes for nice even air flow from the fan.  I really don't see the need to go the extra expense of 8" ducting.  

I will be experimenting with even longer fairly straight ducting runs.  I am going to see if I can extend my ducting so that I can exhaust it into a small greenhouse I set up on my deck to help heat it at night.  The temps here are still dropping down below the freezing mark.  I was surprised last year when a late hard (unforecast) frost killed things even in the greenhouse.  I think this will alleviate that worry.  

I am always amazed at the difference in temperatures at floor level and ceiling level.  Having a good oscillating fan helps to keep this air mixed up so that it does not stratify into heat layers.  But the cooler air will always be at the bottom and the hotter air will always rise.  So, it is quite important to do as lyfe mentioned with intake low and exhaust pulling from high as possible.


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## Hackerman (May 5, 2014)

This is why the call it dope......

I go to the store and I buy 30 feet of rigid duct, some elbows and other assorted goodies to do this exhaust thing all the way from the grow room to my workshop across the basement.

I get home and I take down the ceiling to install everything and I notice that the cold air return is RIGHT above my room. LOL How could I have missed that all the times I looked up here. I don't know who first called it dope but..... they were right. LOL

So, I am going to exhaust right into my cold air return. The grow room uses a carbon filter plus the furnace has a filter so I don't think I'm going to have a problem with odor (I hope not).

Now, the current question is, what's the best way to cut a nice round hole in a sheet metal duct so I can install a tap. I was thinking one of those rotary cutters would work nicely.

Can't believe myself, sometimes. LOL Back to the store again tomorrow.


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## Hackerman (May 6, 2014)

Well, that went amazingly smooth. I am anything but a handyman and jobs like this usually turn into a nightmare for me. LOL

Piece of cake. Cut the hole. Put in the collar. Attached the flex to the fan. Bingo, I'm exhausting into my cold air return. Can't believe I didn't do this years ago. LOL

Thanks again to everyone for the motivation and assistance. My room is upgrading nicely thanks to all of you.


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## sawhse (May 7, 2014)

Awesome man. :48:


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