How to combat cold grow box temps with exhaust letting in freezing outside air

evergreengardener said:

OK OK I see what your saying. My exhaust runs 24/7 so that my carbon scrubber runs 24/7

Click to expand...

Yes i run 24/7 also, but he runs 20m/hr in a cold environment

Im completely open to any proven setup, I really dont need a carbon filter as it will exit at the top of the house and I have no close neighbours. I will see what good reading I can find on ventilation. There isnt much out there I could find relative to my grow though, most Ive read is people using high powerred exhaust because it seems the norm is to run HID lighting which needs extensive cooling.

I really only need airflow replenish the c02 for the ladies and to hopefully keep the smell from coming out of the intake, need some "just buy this and shut up" advice from the veterans

There is also something called a backdraft damper. Google it. I use them. I live in canada.

There is no quick fix 'just buy this and shut up'. There is no proven setup. Everybody's situation is different and you need to tweak your setup until you have it sused. IMO we do not have enough info on your setup and environment to give you specific advice. Depending on how hot and how cold it gets you will need to regulate the exhaust and intake with timer and also by the size of fan you choose. The PC type exhaust fans are good if you want to have exhaust on 24/7. Can you intake straight from outside as well as from the loft? Does the loft get really hot in summer? If it gets too cold so that you need to shut off exhaust then you get negative pressure and therefore smell into the loft...this smell can be neutralised with an odor neutraliser like 'ona' . Good luck!

I live in Minnesota, and I had this problem. I use a section of heavily insulated 4" flexible duct. I wrapped it in fiberglass, and installed a one way flap. On that I added a bit of weather stripping too.
The duct gets a little cold, but not bad. It makes for some pretty colors.

AFter doing some research on charcoal filters, it doesnt even sound like it is a necessity to vent to outside if I run a charcoal filter, I could intake and exhaust right in the loft. For the extra $60 it costs for the filter, seems like a good trade off for not having to fight the cold

Hot goes to cold. You don't need to worry about cold air infiltrating as much as hot air escaping. My opinion/ choice would be to exhaust out hooked up to a t-stat with a damper.

I take it that if its has cold has i know it gets in canada,then you will be heating the house be it with a fire or heating of some sort ,dont pull air from out side pull it from the room,Water heaters are brilliant for hating grow room,and cheap to run

Morriston55 said:

AFter doing some research on charcoal filters, it doesnt even sound like it is a necessity to vent to outside if I run a charcoal filter, I could intake and exhaust right in the loft. For the extra $60 it costs for the filter, seems like a good trade off for not having to fight the cold

Click to expand...

you don't need to vent out side vent into the out side of the room into another room ,i vent into the room my room is built in if you get me.It's a pitty that you can't use two room's so the plants would have there own area like two plants 2 lights 2 small rooms one comes on at 6 in morning and goes off 6 at night the other comes on at 6 at night and goes of 6 in morning that way you are keeping that area perfect temp wise,also vent into a other area of the house use the heat to help heat the house,just get a good filter,Same with veg have it so that one room would be on during the veg lights of for 6 hour and the other,room would trip on for there 6 hours of darkness when the other comes on........

Something to think about,for the future this would work.tyke

Where I live it gets down to -30 regularly through the winter, but I bring in fresh air from outside and exhaust outside for 15 minutes every hour during lights on. I use backdraft dampers. They work great.

To prevent condensation on the intake duct, I just put the intake damper right underneath the exhaust damper, where they are set in a window. The hot air being expelled warms the cold air coming in, right at the window, just enough to prevent condensation. Also, I pipe that intake air, which is still pretty chilled, into the top of my tent where it is the warmest. And I exhaust from the bottom of my tent.

Works great. And it could work in a smaller environment if the cold air is brought in more slowly.

Gquebed said:

Where I live it gets down to -30 regularly through the winter, but I bring in fresh air from outside and exhaust outside for 15 minutes every hour during lights on. I use backdraft dampers. They work great.

To prevent condensation on the intake duct, I just put the intake damper right underneath the exhaust damper, where they are set in a window. The hot air being expelled warms the cold air coming in, right at the window, just enough to prevent condensation. Also, I pipe that intake air, which is still pretty chilled, into the top of my tent where it is the warmest. And I exhaust from the bottom of my tent.

Works great. And it could work in a smaller environment if the cold air is brought in more slowly.

Click to expand...

So you have essentially a HRV ; a fresh air exchange unit
https://en.m.wikipedia.org/wiki/Heat_recovery_ventilation

resinhead said:

So you have essentially a HRV ; a fresh air exchange unit
https://en.m.wikipedia.org/wiki/Heat_recovery_ventilation

Click to expand...

Wow. I guess i am smarter than i thought...lol

And to think it was an accident too. I set it up that way because of restrictions in my basement...and discovered later, when winter hit, that i didnt need to make any adjustments for condensation....