Fresh Air Thru Roof Vent?

[voucher]

I'm growing in an old bathroom in my garage (was set up as an in-law apt). It has a frosted glass window, but I covered it up with plywood so I wouldn't have any light in there when I don't want it. It is a 4'x8' room with exposed plumbing holes, and an exposed 2"ABS vent tube that goes from the floor to the roof. I also have a second pipe going to the roof for the sink, but I would need to open up the wall to get to it unless I hook right up to the drain. I figure that could be done for exhaust.

I want to cut it, cap off the lower end, and run a fan thru the top part, to suck in air from above the roof.

So I have a few questions.
Is this safe? No water is flowing down the drains, so it shouldn't need to be vented.
What is the cheapest, and/or the best fan for the job?
How many CFM of air can I push thru a 2" pipe?
I know I won't be getting much water down the pipe, but it still is a concern. (condensation, rain) How do I address this issue?

 

[Hogdady]

So I have a few questions.

Is this safe? No water is flowing down the drains, so it shouldn't need to be vented.

Safe? Certainly.

What is the cheapest, and/or the best fan for the job?

Rarely does cheapest and best describe the same item

How many CFM of air can I push thru a 2" pipe?

Not much.

I know I won't be getting much water down the pipe, but it still is a concern. (condensation, rain) How do I address this issue?

A raincap.

 

[voucher]

Ok, I guess my best bet would be to use that as an intake, and venting to the other room. I know I will need a filter to cut back on the smell once I start flowering, and I'm working on a filter. Just getting some things together first. I still need suggestions for a fan. It's a 4x8' room with a 8' ceiling. What is a good, inexpensive fan?

 

[Hogdady]

Before you decide on ventilation, you need to decide how much lighting you will be using. Lighting = heat = ventilation requirements.

 

[voucher]

Thank you for your patients, and your quick response.

I currently have 96 watts of CFL that I'm using to help control the heat. I have a 250w MH that I had to stop using because I couldn't keep it under 90 in my grow area. As winter gets closer, temps won't be an issue anymore. right now we have highs in the mid 70's and lows in the 40's to 50's. The room won't drop below 70 with me putting a fan in the doorway for a few hours. This isn't always practical, and I think my plants are suffering because of that.

 

[Hogdady]

Well, if temperature control is not an issue, you could get by with a 50-75 cfm fan and ducting. You have approx 250 cubic feet in your room, and exchanging the room volume every 4-5 minutes is sufficient to replace depleted CO2.

 

[jandre2k3]

I want to cut it, cap off the lower end, and run a fan thru the top part, to suck in air from above the roof.

So I have a few questions.
Is this safe?

To add to Hogdady's response, I would get a filter of some sort. Just remember that the higher in the air, your fresh supply is, the greater the wind speed is that caries particulate matter across the opening of the pipe. That also means that there is LESS wind speed needed to carry such particulates because of the proximity to the ground. For instance, it takes a wind speed of 5-7 mph to keep a piece of paper aloft, but almost 4 times greater than that to lift it off the ground. Pollen, spores, mites, and bugs all ride the currents of wind. You can re-purpose a HEPA filter ($15USD / 2 filters) easily if you're industrious enough to fashion a box for it.

How many CFM of air can I push thru a 2" pipe?

You'd be surprised at how much can get through there. The question is not how much, but how to diffuse it once it arrives in the grow space. The filter should do that quite nicely, just make sure to put a fan on that doesn't go over the rated CFM of the filter, or you'll get blow-by and risk spores, pollens, and other nastiness that you don't want in your area.

I know I won't be getting much water down the pipe, but it still is a concern. (condensation, rain) How do I address this issue?

The local hardware stores sell rain caps for next-to-nothing the ones with screens are the ones I'd go after to screen out any larger debris that might get otherwise sucked down the pipe.

As for the condensation, if you find the humidity is too much in your area, bite the bullet and get a little dehumidifier. A area too humid is a breeding ground for molds, mildew, and bacteria.

What is the cheapest, and/or the best fan for the job?

Look into In-line fans or duct booster fans, 90 to 100 CFM are pretty cheap, and will do the job, just make sure, again, not to go over the rated CFM of the filters you pick up. On second thought- get the fan first, then go get the filters with a higher rating than whatever fan you pick up.


Just trust in the fact that whatever money you spend right now, will more than pay for itself vs. reacting to any health problems that might arise from ignoring the dangers.

 

[voucher]

Thank you guys for the great info. I will keep you updated. I only have 2 clones in the room right now. I got them potted in some 14" pots I picked up from home depot. I also picked up some Kelloggs potting soil there. As winter gets closer, I will be switching to my 250w MH bulb.
Does anyone make a conversion bulb that will let me run a 250w HPS bulb with my current ballast/hood?

 

[Hogdady]

Does anyone make a conversion bulb that will let me run a 250w HPS bulb with my current ballast/hood?

I've never seen a 250w conversion bulb.....

 

[TorturedSoul]

They're not as common as the MH conversion bulbs that operate on HPS ballasts. And neither seem all that common these days, with digital ballasts being both reasonably inexpensive and popular; and of course switchable C&C have been available even longer.

Hortilux makes - or at least made - them. The Ultra Ace are HPS that run on MH ballasts (and the Metal Ace are MH run on HPS ones). The 250-watt one outputs ~220 watts after conversion(?) losses. From the price, Hortilux must think they're made out of gold, diamonds, and the sighs of virgins; prices of $75-95 are common, lol. Not the world's best bargain when a 250-watt Lumatek (or other) digital ballast can be had for around $110 (or a 400-watt for about $10 more and run it at the 250-watt setting until you're ready to upgrade GR size). The product code is HX62443 if you want to fish in Lake Google.