vent question

[dontknowmuch]

ok so I could use some suggestions please, I have 4" vents through my exterior wall. When lights are on I keep them open for cool and fresh air. Here is my problem. When lights go off I have to put end caps on the vents to keep cool air and light out. So every morning and night I have to manualy cover and uncover the vents. Any ideas how to bypass this madness? I would like to keep these passive intakes and not have to add duct,fan and damper

 

[Lemon Jack]

Would it let too much cold in? Because you can use an elblow to block out the light just paint the inside black and face it downward.. . Hope that helps I don't really know how to keep the cold out...

 

[The Hemp Goddess]

How large is your space and what type and size light are you using? You need more than passive vents. You should be exchanging air all the time the lights are on. This means using an exhaust fan to exhaust old CO2 depleted air and bringing in fresh air.

It is easy to make a light trap as Lemon Jack mentioned. If you use ABS plumbing fittings you don't even have to paint them black. You may need more than 1 90 to make it totally dark. Do you have any kind of flaps on your vents? You could use a dryer (or similar) damper vent that opens when there is air flow against it and closes when there is not.

 

[Lemon Jack]

I did assume he had an exaughst fan already sorry. Ya passive intakes alone will not suffice.

 

[dontknowmuch]

Assume away because yes I do have an exhaust fan. I have a 4x4x7 tent,600w hps, 6"inline fan, in a small room. There seems to be plenty of air coming from outside when vents are open ( I would compare it to having a window wide open) And winds seem to always be pushing it in my direction. Sometimes if the temps go over 80 I run ducting from the vent into tent. Other than that my theory is the air that comes in the room gets sucked into the tent and out the exhaust. The elbow trick sounds great for light but room gets too cold if air from outside comes in during lights out. My main concern is for the couple nights I am not at home won't be able to open the vents.

 

[dontknowmuch]

Just a thought. I have a little duct booster fan. Could I attach that to one of the vents, put a damper on it, then put it on a timer?

 

[stevetberry]

What if during the winter you use your passive vents on the tent to bring the air in from the climate controlled room that the tent is in (assumed) and exhaust the hot air out the vent. You could do it this way when it is cold outside and then change it up when it is not.

 

[dontknowmuch]

I vent the hot air into my living quarters and not sure where else to get fresh air but from outside

 

[BlueNose]

you need something like this

hxxp://www.conservationmart.com/p-505-fantech-backdraft-damper-spring-loaded-rsk4.aspx

my fan and light are on the same timer so the damper closes when they both shut down for the night.

 

[stevetberry]

I am sure that the way that I do my exhaust is not the best but in the winter (I have two fans in my attic) I pull air from the grow room across the lights and back into the middle of the house with one fan and the other fan pulls air from the grow room and expels it outside. Like I said this is probably not the best way because you are pumping heat out of the house but I am also pumping the warm air into the house.

 

[dontknowmuch]

Steve how are you getting fresh air into your grow?

 

[stevetberry]

With the fans running there i a little negative pressure on the house and the fresh air comes in from every crack that it can find. I pull fresh air from the crawl space when the temp is OK but when it is cold I do it this way.

 

[dontknowmuch]

Im on a slab no crawl space

 

[smokster42]

Much. Are you drawing air into your space passively? Does your exhaust fan run when the lights are off? If you are dealing with outside air that is being pushed into the tent from the wind then you could try a couple of different things IMO. 1. You could extend 4" flexible tubing in an s pattern using say 8-10ft. This would make it tougher for the wind to push through, but will make it harder to draw passive air through. or 2. You can build a damper with a piece if 4" duct pipe, piece of sheet metal cut round to fit inside, and a piece of small tubing for the center shaft. I mention building your own because I and alot of the peps on here seem to custom build our own stuff because what we need is not always available. Or you can buy a damper and close down the vent so that you get a happy medium of just enough air when lights on/off. Also, if not already, put your fan on the timer with your light so it shuts off with the light. I'm thinking the only way a flapper would help is if you were having a problem with air coming back through your exhaust opening. Extra legths of flex tubing also is a VERY good muffler on your fans. I have extra lengths that I make sure they turn or U shape before they exit the house and you can hardly hear my fans running outside, and are quieter inside the house. Just whats works for me. Peace and good growing...

 

[dontknowmuch]

yes they are passive into the room where my tent is, then when lights are on the fan sucks it into the tent and vents out to my living room. When the lights are off I have to cover them up or light and cold temps get into the room that my tent is in. Don't think a damper is gonna work on passive vents, unless somehow I could create a robot to shut them for me

 

[Growdude]

Here is what you need "hxxp://www.plantlightinghydroponics.com/motorized-dampers-c-76_553_554.html"

Use a timer to open and close them.