Exhaust outside or intake fresh air? Which is more important?

[thirdeye]

If you had only one port to the outside would it be better to use it for exhaust (449 CFM Vortex exhausting from tent using 600w), or use it to bring in constant fresh air and just exhaust into the basement? Why?

I'm trying to gauge the importance of each. I was going to use it for exhaust, but I'm not sure now. If I used it for intake, I'd have to heat it some way as it would be too cold in the winter. Thanks for the help.

 

[FreezerBoy]

I'd bring in fresh air. One, because fresh air is better and two, because exhaust makes noise. I grow in the garage. Winter temps in the 40s aren't unusual with occasional dips to freezing. When it gets bad, I choke off one intake and throw a heater in the res.

 

[thirdeye]

Thanks for the advice. I'm not too worried about noise in the basement. I don't think I'd notice. Temps around here can dip below zero occasionally. Is there a way to apply heat to the ducting so the air temp is at least 55F at intake? I thought I read about heating wires or something once? Thanks for any help.

 

[FreezerBoy]

0º? Holy @#$%*! That's colder than I'd counted on.

Where does the outdoor vent reside? Floor level window? Out the roof?

 

[thirdeye]

It's a ceiling level vent in the basement.

 

[Philosophelon]

I live in a similar climate to you, and I never use any ventilation into or out of my house in the winter. It's too damn cold to bring any outside air in, and I don't feel comfortable with steam billowing out of a vent in my basement 18 hours a day all winter long from my exhaust. So for my air-cooled lighting, I intake cool air from my basement, and exhuast the hot air into my forced-air heating ducts to recycle the heat.

In the summer, I'd probably use it for exhaust, because otherwise you're pumping alot of heat and humidity into your house.

 

[thirdeye]

I live in a similar climate to you, and I never use any ventilation into or out of my house in the winter. It's too damn cold to bring any outside air in, and I don't feel comfortable with steam billowing out of a vent in my basement 18 hours a day all winter long from my exhaust. So for my air-cooled lighting, I intake cool air from my basement, and exhuast the hot air into my forced-air heating ducts to recycle the heat.

In the summer, I'd probably use it for exhaust, because otherwise you're pumping alot of heat and humidity into your house.

Damn, I never even considered that. What did you do? Cut a circle in the side of the heat duct and attach your exhaust?

I do wonder if steam will be spewing on real cold days. I just put up 20 ft. of ducting going from my tent to the outside. I could have done it with 5 ft., but I thought the extra 15 ft. would help cool the air somewhat before being expelled. Will I still get steam? Not sure if it matters, but the humidity around here is low most of the time. Is all that steam from HUMID hot exhaust, or just hot exhaust? This is getting complicated ... shouldn't have smoked that dube.

 

[Philosophelon]

Yeah, I just cut a hole in the square forced-air heat ducting, and epoxy a flange to it. Then just hook your ducting up to it -- it exhausts right into your house, adding heat which is nice in the winter. I don't know if I said it in the last post, but the intake was just filtered basement air. Also, I positioned the blower near the intake, and pushed air through the hoods -- so that I would have positive pressure, because even with recirc. carbon scrubbers the room atmosphere will have some smell to it -- and while I love the smell of my gardens, I just can't have it in the house .

In the spring when you want to unhook it, just seal the hole with a square of sheet metal.

Regarding humidity in your exhaust:
Your plants will always add some humidity to the air in the grow room before it is expelled by your blower. The amount of moisture added to the atmosphere depends on the temperature in the garden and the surface area of leaves (or their underside, as it were) present in the room. If you are just exhausting your lights and not your atmosphere, the RH of the exhaust will be close to that of the intake but lower depending on how many lights ya cool.

I was only running a 50 sq. ft. canopy at the time, and I had steam, because the air was pretty humid -- although I was venting an A/C condenser & compressor and not my room atmosphere. Had to just vent the A/C straight into the basement. I suppose I could have ran that into my forced-air ducts too, but I didn't cause I was worried about the humidity causing mold or some shit in my ducts.

Wow, I am really high and rambling on this evening. Honestly, I don't think that you'll have a ton of humidity to deal with if you don't have alot of plants. Unless your tent is really big your fan will exchange the air pretty frequently, so the atmosphere probably won't be able to build up very much humidity, so you may not get steam like I did. I'd test just in case though, I almost pissed my pants when I went out and saw my vent steaming in the morning -- guess the neighbors thought I was doing a little early morning laundry for a while.

 

[thirdeye]

"I almost pissed my pants when I went out and saw my vent steaming in the morning ..."
LOL!

Hey, thanks for all the info. I'm not too keen on cutting a hole in my heat duct...yet. I'll try ducting to the outside first and see if I get any steam. Hope it works.

 

[moses224]

excuse my ignorance but don't ac and heat run same duct ??? if so heat would be running anyways in winter and ac in summer maybe im missing something but i was planning exhausting thru the dryer vent.to do this i have to run ducting right along ac duct so from what im reading i don't need to cut thru additional walls / ceilings to get to dryer vent instead .....just into existing duct ??? no???? does that make any sense?? again i don't know s*it about hvac so just trying to make it as easy and complete as possible1

 

[fishheadbob]

Thirdeye, on your original question... I think it matters what your basement air conditions are to begin with. I exhaust and also pipe in frigid air, but my growroom is close to the wood furnace so I need cold air. 2 different holes in the wall.
Philosophelon, I can't figure out how you keep your exhaust from stinking up your house, but you seem to have it covered. Like you said, "really high".
Moses, dryer vent is flimsy stuff. Trying to splice a Y into it could turn into a really leaky job, and I wonder if your Mj exhaust might back up into your laundry stinking it up. Go to Lowes or Home Depot and poke around in the drier vent department to get some ideas on what you're thinking about. Take a look in the hvac dept. while you're there, they tend to have solutions for problems I didn't know existed. If your grow is in close proximity to the laundry, you could probably make it work, but I'd seriously think about buying the entire dryer exhaust kit for $20 and knock another hole in the wall if you can keep it discreet. But I'm a serious DIYer.
An afterthought about venting into a dryer. Bad idea. Dryers push out a lot of lint, some of that lint is going to back up into the growroom exhaust plugging it sooner or later. Also don't vent into a chimney used for heating, carbon monoxide problems could possibly occur although people do it.

 

[moses224]

Thirdeye, on your original question... I think it matters what your basement air conditions are to begin with. I exhaust and also pipe in frigid air, but my growroom is close to the wood furnace so I need cold air. 2 different holes in the wall.
Philosophelon, I can't figure out how you keep your exhaust from stinking up your house, but you seem to have it covered. Like you said, "really high".
Moses, dryer vent is flimsy stuff. Trying to splice a Y into it could turn into a really leaky job, and I wonder if your Mj exhaust might back up into your laundry stinking it up. Go to Lowes or Home Depot and poke around in the drier vent department to get some ideas on what you're thinking about. Take a look in the hvac dept. while you're there, they tend to have solutions for problems I didn't know existed. If your grow is in close proximity to the laundry, you could probably make it work, but I'd seriously think about buying the entire dryer exhaust kit for $20 and knock another hole in the wall if you can keep it discreet. But I'm a serious DIYer.
An afterthought about venting into a dryer. Bad idea. Dryers push out a lot of lint, some of that lint is going to back up into the growroom exhaust plugging it sooner or later. Also don't vent into a chimney used for heating, carbon monoxide problems could possibly occur although people do it.

When i say dryer vent i mean remove dryer and just use hole and vent in wall i would rerun all duct and all i would have is a sink in the laundry room to fill up pots, etc... I was just saying instead of going out of grow room into attic then back into laundry room then out the laundry vent hole I would just tye into the ac duct work which is existing. attached was my idea but may revise based on this conversation

 

[LolaGal]

An idea I had for heating the intake vent air if too cold.

Put those plug in water pipe heat wrap on the intake vent...should work to heat it up for intake!

 

[Philosophelon]

Philosophelon, I can't figure out how you keep your exhaust from stinking up your house, but you seem to have it covered. Like you said, "really high".

In the instance I'm describing, I was running a sealed room, and I had my cool tubes on their own exhaust, um... circuit? (wtf is the hvac word for circuit?). Anyway, the intake was just filtered basement air that was pushed by an 8" (it may even have been a 6") centrifugal blower through some cool tubes and exhausted into my heat duct. Because I pushed the air through the hoods, there was positive pressure in the ducting and hoods, so no stink gets sucked into that exhaust circuit.

Also, I had the lamp cords from my ballasts hardwired into the cooltubes, and sealed all the leaks w/silicone. I didn't notice any positive pressure in my grow room -- there may have been an undetectable amount -- but I had a VaporTek (a boxish thing with cylindrical odor neutralizing cartridges) in the basement so even if a little smelled leaked out of my growroom, it wouldn't have been noticeable.

Moses - Yeah, you could run your exhaust into your heating ducts year-round, but then you will be running hot air into your house in the summer, especially when your central A/C turned off. Your central air has its air-cooling element near the furnace heating element, so if you pump hot air into the duct further away from the furnace, it will not be cooled by your A/C. I don't think it is possible or advisable to pump air into your furnace before the A/C cooling element. Hope that helps a bit, HVAC ain't exactly my thing either.

 

[moses224]

In the instance I'm describing, I was running a sealed room, and I had my cool tubes on their own exhaust, um... circuit? (wtf is the hvac word for circuit?). Anyway, the intake was just filtered basement air that was pushed by an 8" (it may even have been a 6") centrifugal blower through some cool tubes and exhausted into my heat duct. Because I pushed the air through the hoods, there was positive pressure in the ducting and hoods, so no stink gets sucked into that exhaust circuit.

Also, I had the lamp cords from my ballasts hardwired into the cooltubes, and sealed all the leaks w/silicone. I didn't notice any positive pressure in my grow room -- there may have been an undetectable amount -- but I had a VaporTek (a boxish thing with cylindrical odor neutralizing cartridges) in the basement so even if a little smelled leaked out of my growroom, it wouldn't have been noticeable.

Moses - Yeah, you could run your exhaust into your heating ducts year-round, but then you will be running hot air into your house in the summer, especially when your central A/C turned off. Your central air has its air-cooling element near the furnace heating element, so if you pump hot air into the duct further away from the furnace, it will not be cooled by your A/C. I don't think it is possible or advisable to pump air into your furnace before the A/C cooling element. Hope that helps a bit, HVAC ain't exactly my thing either.

got ya. in reallity i would be pumping in ac duct for it to come right back in. That said what do you think about pulling out a vent in living with 10" split it and one line goes to lights and one to room for "fresh air" would this just be to much cold air coming out of living room or do you think it could work. The living area im referring to includes an eat in kitchen about 650 sf of area?......just trying to eliminate all area inside before i go out....thankz

 

[Philosophelon]

I think you might be OK if you don't have a very big fan, but why not vent from the basement, it's usually cooler. Also, if you are pulling too much air out of your living room and exhausting it outside, your furnace will have to work much harder in the winter, because you'll be pulling so much air from your house. If you just recycle the exhaust back inside the house it's like a closed circuit so you won't lose heat.

 

[thirdeye]

"An idea I had for heating the intake vent air if too cold.

Put those plug in water pipe heat wrap on the intake vent...should work to heat it up for intake!"

Those are the kinda' tips I'm lookin' for! thanks. Next time I'm at the home de pot I'll look for those.

 

[moses224]

Philosolphen - no basement just attic area or i would.

Thirdeye that sounds like an idea but im not aware of what your saying enough to comment. If you get any more info lets explore that may be it

 

[fishheadbob]

No basement, just attic. Moses... dryers are mighty nice things to have, you remove it to grow weed you're decreasing your quality of life, and Mrs. Moses is going to cast you out. Perhaps you could merely vent into the attic if it's not living space. Don't know where you live, but here in the frigid Northeast attics are unheated and VENTILATED. It's a roofing/moisture kind of thing, but the temp in my attic is about the same as outdoors. When I had the new roof installed they put in more vents and breathable soffets (? I think they're called soffit, maybe fascia ?) so the air continuously turns over up there. Don't know where you are or how they do it there. Just a thought.
About maybe bringing in too much cool fresh air; that can be easily handled by making a damper for your cold air intake. While you could go nuts in the hvac department and buy something expensive, you could also just block some of the air intake with a piece of paper or cardboard. I've never experienced air that was too cool, even when it is below zero outside.