Ventilation Question

My set up is in a basement, underground. No windows, no way to drill into another room, not even a dryer exhaust. Right now its peaking at 81, with 73 at night. Not a disaster situation, but still a little on the warm side. The way I see it, I have two options. Vent under the floor boards, or possibly tap in to the furnace exhaust. Considering there is a dryer in the room, I do not think it is a good idea to vent under the floor boards. With that said, Im leaning toward tapping into the furnace exhaust. The exhaust goes up to the roof and out, chimney style. There is also a water heater which is exhausted the same way via the same duct work.

Would it be a bad idea to tap into the furnace exhaust? Would this interfere with the furnace performance? FLIR thoughts? Am I an idiot for doing this?

If you run under floorboards your will get mold because you are putting out a lot of moisture.
If you have no way of exhausting air look into a closed/sealed grow room, with this system you need to have an AC running and a Air purifier with CO2. Its a fully controlled environment for optimal conditions.

I found a link for you
http://www.cannabisculture.com/articles/3368.html

Thanks the article was helpful.

My set up is in a cab, so in a sense it is a closed environment. However, there is no connection to the outside world. The problem Im having is that the hot air being exhausted 20 ft away from the cab is raising temps in the room, therefore my intake is pulling in hotter air.

So is tapping into the gas furnace exhaust a bad idea? I understand that the risk is that backflow from the furnace could be pushed into the grow area. For instance, if one were to hook up a bathroom exhaust to the furnace exhaust the furnace may exhaust into the bathroom when the bathroom exhaust fan were turned off. However, the grow exhaust fan runs constantly so I don't see how this backflow could happen.

We are dealing with a small space. Im trying to avoid the additional cost of running AC.

Lets rule out the floorboard idea due to occasional high humidity.

I think you can buy adaptors for dryer ductings and the like that has a circular opening with a disk on the inside, and when there is air being blown out it opens and as soon as it stops the disk flips around and shuts off air being vented back in.

Im trying to make this as simple as possible. There has to be some HVAC people out there. I cant seem to find anybody who has reported doing this, and I know there are tons of basement grow ops. With such a simple idea, there has to be some problem I am missing.

Will hooking up my garden exhaust, 400+ cfm, to the furnace chimney exhaust create problems such as spillage of carbon monoxide into the house?

The garden exhaust will run constantly, so I do not see how backflow could create a problem. I am however, worried about negative pressure.

I read about someone using their water heater vent a long time ago... let me dig through my archives and see if I can find it.

While I'm searching, do you have access to a plumbing vent stack? I've seen that utilized for exhaust from a basement or crawlspace grow.

buy a water cooled heat exchanger for your exhaust and have everything inside CO2 ac air purifier

Here's a pic from an old forum showing the plumbing vent stack idea

if your in your basement dont you atleast have small vents on the side of your house? i thought that was code everywhere?

but i have heard of people heating there whole house using grow room heat in winter

No vents in that room, its completely underground. There's not even a vent for central air / heat. Which is the big problem. The air in that room doesn't really move much. There is some circulation, but not much.

Any heat expelled is drawn back into the cab, eventually. Rather than drilling into another room, I would prefer to go up the chimney and out. There is ducting which comes out of the chimeny and splits. One section goes to gas water heater, and the other to the gas furnace. I am hoping that I can split the section that goes to the furnace and use it to ventilate the cab. I would push 400 cfm through it.

There are two big problems I'm thinking. First, is that if too much air is forced out, air must come in from somewhere. So cold drafts in winter time will increase. In an air tight environment, this could create a draft to come down the chimney, creating a dangerous environment, carbon monoxide poisoning. This place is by no means air tight, so not really to concerned in this aspect. Second, the amount of air being pushed out the chimney creates pressure. Like blowing air through a straw. If the chimeny flue cant handle this, the air is pushed out whatever opening is available. When this happens, all of the pollutants from the gas furnace and water heater are not exhausted, again creates a dangerous environment. This is my big concern. Will the water heater and furnace still exhaust properly if I split the exhaust of the furnace to ventilate an additional 400cfm?

What to do... right now Im hitting 81-83 during full blast lights on, and 73-76 with lights off. Res temps are somehow staying in the 70's.

i would try to hook it to the flu pipe but u should do it befor the water heater and furnace so you dont affect there flo.. it wont hurt to try!! whats the worst that could happen?? just keep a close eye on it @ first...

also i wouldnt worry about cold drafts much only run your fan durring lights on time...

good luck with this it sounds like a tough one.. can u show some pics of your space?

yea pics would help. im sure theres a simple place you can just cut a hole and vent to where it wont cause problems

Well give us more information so we can help you with a real answer. Things we need:

Grow room dimensions (height, width, and length) or cubic ft if you know it.

current water heater/furnace exhaust size

dimensions of entire room (inc grow room)

are you introducing co2?


Im not entirely sure what you are so paranoid about. If the room is as ventless as you say no air will come down the chimney or it would already be doing so. if the furnace is on while the fans are it could mess with the flow. If the exhaust tubing is large enough it should accomidate both. as for where to draw in the air, most likely from floor vents, cracks and seams.