Exhaust and ventilation Issues. Need some help!

I currently have a 400w hps in a closet. I would like to keep the closet doors closed, however the temps quickly rise to 90+ when I leave it shut. There is an attic space above the closet that could be accessible, would it cause any problems if I vented the heat into the attic from the 400w?

I also have no way of bringing in fresh air from outside directly into the area. If I were to buy a grow tent and place it into the space, what kind of ventilation would I need for that? And would I be able to keep the closet doors closed with the tent inside if I was venting the heat into the closet instead of into the attic (if thats not possible).

If you want hot air to leave then cold air air must come in..somehow. I think the best thing would be to tale air from the adjacent room. Just mount a 90 degree elbow in the closet (spray paint the inside flat black) and put a normal looking register cover on the outside wall.

You could even do that on the wall that is next to the closet with a little ducting

If you can vent into the attic above, then you can draw air in from the same place. Two holes for vent ducting in the ceiling of the closet will allow you to seal the door shut completely if you wanted. If the holes are cut closest to the door, you almost have to be inside the closet to see them. Make sure the attic has vents to the outside. You can run ducting all the way to the attic's vent(s) if you wanted. It would prevent recirculating the same closet air.

"And would I be able to keep the closet doors closed with the tent inside if I was venting the heat into the closet instead of into the attic (if thats not possible)."

-- A tent alone won't do anything for the temperatures in the closet... hot air would just leave the tent, enter the closet-space, and quickly get returned back into the tent. You'd still have to vent the closet itself in some way and that means ducting or keeping the closet door open. However, a tent in the closet would allow you to leave the door open without light spilling out or light spilling in - which is why most people want to close the door in the first place but is a bit of a compromise if you are trying to hide the grow or be stealthy by using a closet...

Here is your solution to either tent or closet.....

http://cgi.ebay.com/PRIMAIR-TEMPERATURE-FAN-SPEED-CONTROLLER-HYDROPONICS-/220638828157?pt=UK_HomeGarden_Garden_PlantsSeedsBulbs_JN&hash=item335f19567d

Buy some ducting, 2 fans, set your fan speeds on controller, set your desired temp for closet/tent, away you go, room at constant temp, as said before, choices are limited, either you create an intake an exhaust or leave closet open. Good luck.

Thank you for all the help! I think I am going to try to vent into the attic. I know that there is a vent leading outside from the attic. However, I might not be able to physically get into the attic to lead the ducting to the vent. If I just get one hole in the ceiling of the closet and exhaust the heat there, and use a passive intake or a small fan to intake the air that is in the closet....would that work?
I also heard that exhausting heat into an attic could cause problems like mold or something, anyone heard of that?

Im going to try to get into the attic today to see whats up. Ill keep ya posted.

jim beam said:

Thank you for all the help! I think I am going to try to vent into the attic. I know that there is a vent leading outside from the attic. However, I might not be able to physically get into the attic to lead the ducting to the vent. If I just get one hole in the ceiling of the closet and exhaust the heat there, and use a passive intake or a small fan to intake the air that is in the closet....would that work?
I also heard that exhausting heat into an attic could cause problems like mold or something, anyone heard of that?

Im going to try to get into the attic today to see whats up. Ill keep ya posted.

Click to expand...

warm air contains moisture, pumping it into a dark cool place like an attic overtime can cause mould issues within the attic space, be careful, although i doubt the heat from a 400w HPS would be enough to introduce this issue for you, you should be fine...

If you actively exhaust (using a strong enough fan) into the attic, you probably won't need any active intake - AC cooled air from the adjoining room will probably be enough passively entering under the closet door (if it's like most closet doors). Are you going to be using a carbon filter for smell issues?

I will definitely be using a carbon filter for the smell, it is a must. However the house is not AC cooled, no central air, so if I have the passive intake it will be air that is not AC cooled and during summer months it can get very hot in the house. Would the exhaust into the attic still be sufficient in the summer? Fortunately it will be winter soon and temps will more than cold enough for the passive intake.
I would still like to get a setup that is manageable during all seasons if possible.
My ideal outcome would be to get into the attic and exhaust and intake through those vents, but it just might not be possible.
In that case I will need all your creative genius to come up with a solution

Are you using a vented hood or are you just exchanging air? A vented hood takes allot of heat out of your room, or rather, doesn't let it transfer to your room in the first place. The efficiency of that process depends on the temperature of the air your pulling through your hoods (duh). So in the winter, your going to be rockstar. In the summer...your attic air is going to be in excess of 100 degrees so no matter how much CFM, your cooling is going to be less.

The key is taking air from an INSULATED space, your attic, is not. Is the solution i mentioned earlier (put an intake vent from an adjoining room) not feasible? I'm all about keeping the grow conditions ideal as much as I am automating that shit so I don't have to worry about it. Perhaps I am a bit anal (I did make another grower change his clothes before entering my grow room the other day as I know he has spider mites ) but the things I know about and can control, I control.

If that were MY closet I would intake and exhaust to the attic through a sealed hood. This fan is simply hooked to the same timer as the lights. I would install the fan in the attic to reduce noise. Then I would install an additional fan (nothing huge, even $30 in-line "booster" fan) in the ceiling of the grow room and create an inlet down near the floor from an adjacent room. That fan is is hooked to a temperature switch so when it gets too hot, the fan kicks on, draws cool air from the adjacent room, and shuts off when its cool enough.

There is no magical creative solution, its simple physics. I have a similar set-up and the temperature rarely fluctuates more than 2-3 degrees. Do you have a crawl space under your house? If so, I wold cut a hole in the floor and draw air from there.

taking air from a adjoining room is definitely not going to be possible. Although it would be ideal.
I will be using a vented hood for sure. So I was thinking venting up through ceiling into the attic and out the vent. And then running more ducting into the vents and having it pull fresh air into my room. When it gets hot it the summer I will just have to stop the intake. Will that work?

Should work fine if your home AC is decent. I have a 600w (inside a tent) inside of a small closet with just the air being ducted into the adjoining room where it mixes with air from an AC vent. Adjoining room temperature is set for 75f on the home thermostat and tent temperatures max at about 10 degrees over that - but usually run @ just 5 degrees over ambient room temperature at canopy level inside the tent (depends on how high I have the fan speed set at).

I have a 6" air-cooled hood and 400+ cfm inline fan on a speed controller but rarely run it at more than half speed. You should have better results with a 400w and venting to the attic even if you go with less cfm/smaller fan.

Can't wait for it to cool down outside here (still around 90f during the day)...

The thing is I have no AC in my house. I could get a small window AC unit. But I would rather not have to keep that running along with the lights and fans. Is it possible to not use AC and still keep the temp down with just venting during the summer. It is cool enough right now that I don't have to worry. But for future summers it will need to be worked out.
Still 90 where you live?! damn...its already getting down to the 60's here.
Whats the least amount of power i would need for the inline fan?

this thread may help you understand a little better.
page 2 has my explanation for the thread starters scenario.


https://www.rollitup.org/newbie-central/372127-passive-intake-size.html

always exhaust your hot air far away from your grow room.


as long as your inline fan is capable of enough air exchange then it should keep your grow room a few degrees above the ambient room air if you choose to passively pull air into your grow.


J

Thank you! That answered most of my questions. But if I passively pull air into my room, the air quality would be much less than if I was to draw it directly from the outdoors. So i think I will just have a small fan for the intake and have a passive intake as well. Because if I am going to get into the attic and start running ducting, i might as well run an exhaust and intake...

Dont be misunderstood.

Ambient house air has a ppm of Co2 of around 600ppm.

Outside ambient air has a ppm count of only around 300ppm of Co2.

So you are actually better off pulling in air from the house rather than outside.

J

And depending where you live you could pollinate your grow with ditch weed if you do intake from outside, get a window ac unit in your room that the grow is in, if you have the cash you can get one of these. http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias=aps&field-keywords=+air+conditioners&x=12&y=22

Jim Beam

Alot will depend on the temperature of the ambient room that your grow is located in.

With the correct size Exhaust fan with passive intakes, as long as the ambient air that you are bringing in is below 24C then your grow room should stay within 2C-3C of this temperature.

J

Thats great to know. It means less ducting and fans and money!
The summer is a long time away, so I'm sure by then I could pick up one of those AC units. I live in Vermont so the winters will easily take care of the heat issues for the coming months. Thanks for the help!

Nice! Vermont you should have no worry's then Happy grows.