Ventilation set up


Question from a fellow grower:

|Needing advice on how to set up ventilation for a 14.5’ x 11’ well insulated grow building ! The building stage is nearing completion! It will have a air conditioner that is properly rated! Will probably heat with a small propane infrared heater! But how do I bring in fresh air in winter or do I ! Just worrying about the environment I’m going to be maintaining! Worried about mold and so on! Building has no windows and is very well insulated! Thank you so much anything will be appreciated! Lights will probably be a mix of led’s and HPS/MH !|


If you have central air, (unless that is a window unit?) you should be fine. To be honest, I think that if you can breath in the environment, the plants will be fine.

You’ll need plant-specific ventilation (exhaust) to remove heat from lights, and that in itself should provide airflow if the room temps are kept livable.


If you going to bring in fresh air in winter in a cold climate you want a reheat coil on your intake that will temper your incoming air so main heat can comfort heat the space
This can be done with a electric duct heater installed in the intake duct youll need a proving switch and all necessary control wiring
Unless your familiar with setting up theses type of setups it may be worth while to have a local hvac guy set it up so its done correctly and safely
Not sure what type of budget you have
If the building is well sealed and air tight youll need fresh air if its not you’ll should have enough air leakage that you wont need it
If i can assist further let me know
Im a 27 year commercial Union Hvac Mechanic


It is a stand alone building. It is a 159 sq ft room that is very well insulated! It will have a window unit 5-6000 BTU air conditioner and a small infrared heater for winter! Do I have to bring air into the room or if I have 3-5 fans circulating the air will that be sufficient ?


Hi! I have worked both construction and residential heating and air (yeeeeeeeaaars ago) and have grown a few plants, so that is what I’m drawing from.

If you can breathe in the room and the temp is right, that is a good start. Well insulated is awesome as well. Once you introduce lights, you will get heat. If the window unit can handle it then you should be good. You’ll still need fans and stuff.

In the winter when you have to heat it that may be different. The lights may provide enough heat by themselves depending on the size of your grow that you don’t need the heater. But the AC was forcing outside air into the room, If you’re sealed up and weather-stripped for winter, you’ll probably need air from outside circulating - to prevent mold at a minimum.

Something as simple as a HEPA filter set-up (like for a furnace) with a damper, rigged into the wall might work for that. The filter would prevent outside baddies coming in, and might reduce the sheer volume of cold air coming in. With a portable heater in front of it, it might work.

I also think that since you are trying to make it right the first time I would rig an exhaust fan in the ceiling just to be safe. In a 10x6 (close guess?) shed, I would think an 8" fan, but what you buy should have cfm information. If you run an exhaust fan, the air will find it’s way in from somewhere, probably through the AC if you leave it in the window.


I agree that you probably wouldnt need fresh air unless your shed is truly airtight
Definitely need fan inside shed
I run no less then 4 at any give time plus exhaust and intakes
New homes need fresh air ventilators because they are built so tight
@Whodat66 is on point if air is safe for you it will be safe forbthe plants
The ac should help you 6000 may be just enough with the heat load from them
Is the shed in direct sun or in a shaded area ?
Set your exhaust up size to cubic feet of space
I would personally have a intake also set up but have the ability to shit it down if you do t need ot in winter

The propane heater you have is it vented or free standing
Combustion gases are something you want to consider as well @Rick4


Good God! You’ll need 50,000 watts of light at 40 watts/sq ft. For 159 sq ft. I use a temperature controlled switch for controlling air. You can buy them on Amazon. You set the temp, plug in your device and it turns it on at the right temps.


i think u put an extra zero in there. it should have 6500wt for 159 sq ft


Oops sorry. Was thinking of 1600 sq ft. I’d hate to try and get rid of 6.5kw of heat. It would need to be a lot of AC.


hi, I’ve been following this post, its interesting. Like your suggestion for the a/c controller… would you recommend this one I found on amazon?


Mine isn’t like that. It’s made by bayite and it has an outlet for heating and one for cooling. When it gets to the target temp, That outlet is turned on.


The propane heater I planned on purchasing was going to be a vent-less infrared ! Which I sold when I worked at a plumbing and and electrical store and a lot of customers used to heat their house or just a room! Of course I plan on using one that is properly sized! The room has been really sealed with caulking and insulated with batts then 1/2 inch foam boarding under the sheet rock! my budget will get bigger with time but IS limited at this time because of the cost of building the building recently! The lighting I’m starting out with is a 600 watt HPS and 2 1500 watt LED’S actual wattage 265 ! I will place one LED on eac side of the HPS ! Not sure how far I should hang the LED’s from the HPS! Maybe 2 ft ? Anyways I will keep adding lights as I can! My goal is to grow 12 plants cause me and my wife are acquiring our marijuana licenses! I am wanting to dedicate 9-14 sq ft to each plant so they have plenty of room;) ! So anybody who would like to give me some advice I’m all ears! Lol!


Cool, thank you


Dude solid plan
Ok i know the type your talking about and they Are safe :+1:
You may find with the extra heat from lights that you actually need to cold air to help cool the space with light on you can always install a temp control as suggested to switch the intake fan off
You could run lights at night also to help combat the colder temps
How cold is your average night time temps ? In winter
You could get a motorized damper and install on intake to prevent cold air entering when not needed as well they should be fairly inexpensive 50$ maybe
Agian youd need to set up controls to operate it but i could walk you three that if you wanted

As far as light placement i think that the 2 foot mark is probably a decent distance to start with on each side of the hps
I personally would over lap a little bit myself to prevent shadows
A light mover would be a good thing to consider for a future upgrade


Thanks for the info !


That will be a must! Thanks