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Need help on where to vent all my heat

oxenhiven

New Member
First time posting, so if I get something wrong please bear with me.

I have a spare bedroom where I've made a DIY grow tent. It's not pretty, but I think it will do the job. The tent itself is approximately a 4x5 with a 1000w HID. The tent itself is made from panda plastic with the frame is all pvc piping. I've attached a 6" inline fan to suck air from the light, which pulls air from inside the tent.

So here's my problem... All the hot air I've been venting out of the tent goes back into the bedroom, which then is sucked back into the tent via an inlet at the bottom of the tent. The only thing is I'm having a HUGE heating problem. Like, 96 degrees huge. I know plants aren't supposed to be in that hot of an environment, so I stuck them under a bunch of cfls until I can fix this problem.

So here's my tentative solution: I was thinking about exhausting all that air into the garage via the attic (using flexible, insulated ducting). That is, connect some insulated tubing to the end of my fan, have it go through the attic and finally expel out and into the garage.

Th only thing is, I'm wondering if this is going to affect the rest of the house. Honestly, I don't know much about ventilation and heating and I'm afraid that if I take it upon myself to do this, I'm going to fuck shit up.

So my question is, Would this work? Should I vent back into the house, or outside, or maybe somewhere else?

Thanks in advance!

Edit: I think I found a solution to my problem. I don't why this didn't occur to me in the first place (probably b/c I was freaking out so much about the heat), but what I realized is that part of one of the bedroom walls is shared by the garage. I'll simply vent the the air straight into the garage, as opposed to the making it go up through the ceiling, into the attic, back down through the ceiling, and into the garage. It would look a lot nicer, but honestly, it's just too much work, time and $$, so fuck that. Thank you to everyone that has contributed to this thread. It's been a big help just getting it out there. Thank you.
 

oxenhiven

New Member
I would slap a carbon filter on it and vent directly into attic.

This was my very first idea, but I read somewhere that venting directly into the attic may be dangerous because it increases the humidity up there, increasing the chance of mold on the framework.

Also, I've tried looking up this idea and apparently it's a subject the entire internet wants to stay silent on. Maybe I just suck at searching, but if you have some more specific advice it would REALLY appreciated.
 

David Bowman

New Member
:welcome: to :420:

I agree that pumping air into the attic can cause more problems than it's worth, I like your original idea of pumping air through attic into garage. If smell is an issue, use a carbon filter. Make sure that you have a powerful enough fan to adequately push the air into the garage. Alternatively you could mount the fan in the garage and pull the air from the tent. FWIW, we have a swamp cooler on our garage roof that uses a ~20' long 18" diameter duct through the attic to bring the cooled air into the house and this causes no problems with regard to the attic.
 

David Bowman

New Member
I think the air is moving too fast for the carbon to absorb much moisture. I have a new thermometer system with 3 remote sensors, one on top of the thermostatic fan controller, one on top of the canopy lights and one at the exit of the exhaust duct and the temperatures and RH are consistent with one another when the exhaust fan is running. While the exhaust fan is off the duct sensor reverts to ambient temperature and RH levels.
 

PeytonManning

New Member
I see. I figured a small inline fan wouldn't be able to push that hard, especially if there is a lot of length and bends in hose. If you turn your fan controller down does it do any different or is it consistent even then? Om nom nom, more food for thought. Crap, now I'm hungry
 

David Bowman

New Member
I do not have a fan controller on my exhaust system it runs the full 130 CFM all the time. I really haven't needed a fan controller since temps have been a problem for my grows and the exhaust system always runs constantly in an attempt to keep temps under 85°.
 

oxenhiven

New Member
:welcome: to :420:

I agree that pumping air into the attic can cause more problems than it's worth, I like your original idea of pumping air through attic into garage. If smell is an issue, use a carbon filter. Make sure that you have a powerful enough fan to adequately push the air into the garage. Alternatively you could mount the fan in the garage and pull the air from the tent. FWIW, we have a swamp cooler on our garage roof that uses a ~20' long 18" diameter duct through the attic to bring the cooled air into the house and this causes no problems with regard to the attic.

Smell has yet to be an issue, but I do have a carbon scrubber ready for it when the time comes.

As far as the fan goes, putting it in the garage (or just above it in the attic) was exactly what I was thinking of doing. The only question I have is, Is this going to affect the cooling in the rest of the house?. I keep reading about positive/negative pressure when it come to hvac in homes and I'm afraid doing all the work only to find out that all the air is escaping through my homemade job. Do you know anything about this?

As for your swamp cooler, is it creating any condensation within the attic? If the system is sealed, then there's no humidity added in your case. If this is the case, it wouldn't necessarily apply to me, I think.
 

David Bowman

New Member
Most of those issues have to due with 90+% efficient gas furnaces receiving enough oxygen in the newer more tightly built homes. They require independent intake and exhaust in order to be that efficient and with that setup there is no negative pressure in the house from the furnace running like there is with the older 80% efficient models which use room air. Venting outside of the house will create some negative pressure, how much depends on the CFM rating of the fan. My take on this if you are forcing a significant amount of air outside of your house then you should probably have some sort of intake somewhere to minimize any pressure differences.

Actually, I haven't checked the attic to see if the duct system isn't properly sealed but based on how quick it begins to cool and the force of the airflow, I feel comfortable that its integrity is good. But now that you have mentioned it, I probably should check that out once I get the swamp cooler up and running for the season.
 

Calyx Hunter

New Member
I had this exact same issue. I ended up putting my 6" inline blower in the attic as it was noisy. I use this to cool my 600W hood and I pull air in from out side my tent in my room through the hood and tent then I have it ducted to the room vent and then up into the attic. I installed a backflow damper on the end. It does not affect household cooling/heating in any way. The attic is not a sealed environment therefore it creates a negligable positive pressure differential. Colorado air is very dry and I grow on a small scale so my RH stays low and I don't need to worry about moisture in the attic.
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Calyx Hunter

New Member
I forgot to mention the duct coming from the furnace/AC to the room I rolled up and sealed with duct tape. Having that loose and open in the attic would've reduced household heating/cooling efficiency.
 

David Bowman

New Member
My bad. I was under the impression that a carbon filter draws a lot of the humidity out of air going through it. Learn something new everyday here!

I think the air is moving too fast for the carbon to absorb much moisture. I have a new thermometer system with 3 remote sensors, one on top of the thermostatic fan controller, one on top of the canopy lights and one at the exit of the exhaust duct and the temperatures and RH are consistent with one another when the exhaust fan is running. While the exhaust fan is off the duct sensor reverts to ambient temperature and RH levels.

UPDATE: With low RH, under 30%, there seems to be no significant loss of moisture through the carbon filter, maybe 1% or 2%, that's it. When the RH gets over 30% there does seem to be a little loss of moisture due to the carbon filter, ~5% difference in RH, meaning if the grow box reads 40% then the exhaust vent reads 35%. I will keep track of this to see if the loss continues to increase as the RH increases.
 

David Bowman

New Member
Awesome. I'm surprised you kept up with it lol. Yeah I thought it would have brought it down more. Back to the drawing board

I just happen to start up the humidifier for the SS drying and was watching the RH from the various sensors when I noticed a pattern. I wouldn't give up yet Peyton, it may prove to be a much more significant loss as the RH rises.
 

oxenhiven

New Member
I'm not sure why, but I can't seem to edit my post so if you've come here because you have the same problem, I found a solution.

Earlier, I mentioned that I would vent all the heat into the garage. At first, I was afraid of doing this. Mostly because I didn't want to vent all the cold air in the house into the garage, which isn't ventilated. Plus, with all this talk about negative/positive pressure I had been reading on other posts, I was VERY worried that putting a hole in my wall would overwork my A/C Unit as well as increase my electricity bill.

But after inspecting my garage a little more, I realized it was sealed off already, thus any loss of pressure inside my room would be minimal. Had it been vented directly outside, I don't think that would be the case (but I'm not an HVAC expert nor do I really know much about the subject, so take that into consideration if you decide to take that route). So, after saying a little prayer, I went ahead and vented the heat into the garage and, what do you know? It works!

So if you’re having the same problem, I’m here to tell you that doing this is working for me. But take everything into consideration if you decide to do this. I’ve only been doing this for a couple of days, and everything seems fine, so far. But I’ll have to give it some more time before being absolutely certain. But for now, it’s keeping my grow room like an oasis and I couldn’t be happier.

Thanks again for all contributions made to this thread. I’m more grateful than you know.
 
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