Too Much Heat -- Can't Fix Problem

I have posted a few threads on here trying to resolve my heat issue, and I never seem to figure out a solution that actually works for me. I have came a long way since I started having heat issues and trying to fix it, so hopefully this will be the last thread that I have to create about the subject.

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I have an enclosed 4'x4'x6' flowering room located in my basement, which actually does not have any fresh air intake besides the air leaks in the structure and when I open the room. The average temp inside of my flowering room with the lights turned off, is roughly ~74-78F, and with the lights turned on ~84-88F. I have a 315w reflector that is being vented outside of the room back into the basement. Venting my hot hair back into the basement is not the issue, because I have placed thermometers at both locations for air intake and exhaust and the temps are within the average ranges that I have stated below.



Basement Temp: ~72-75F
Room Dimensions: 4'x4'x6'
Lights OFF Temp: ~74-78F
Lights ON / Door CLOSED Temp: ~84-91F
Lights ON / Door OPEN Temp: ~79-81F

Here are the two fans that I am using to push air just through through my 315w reflector:

Extraction: 334 CFM Can Max Fan ( https://www.amazon.com/gp/product/B004C2IWIE )
Intake: Lowes Inline Fan ( https://goo.gl/Vfhdzn )

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I decided to see what would happen when I left the door to the flowering room completely opened for passive air intake, which there was not much change in the grand scheme of things, however, where the thermometer is located it went from 86F to ~80F. It would appear that even leaving the door completely open is not enough to effectively cool down the room. I left the thermometer out of the range of the light coverage, because I have been told this could warm up and give false readings. You can see my thermometer in the first picture strapped to the stud with some green garden twist ties, however, I typically leave the thermometer clipped onto the LED panel, which sits way lower than the CMH and the temps get awfully hot and makes me wonder how a plant could even survive under the CMH fixture.



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From my understanding here are the possible routes that I could attempt:

#1). Air conditioning. I could get a smaller (portable?) air conditioning unit, which has a thermometer built-in that can maintain the temperature by starting and stopping when needed. I am a bit concerned with this route as it's more expensive, and will need to be running to cool the area down. My thoughts are that since the room does not have air circulation that it will have to run less often to keep the flowering room cooled down

#2). Add actual ventilation for the room air exchange, and simply not the light reflector, which means I would need to purchase two additional fans for proper air exchange. There was ventilation for the actual room air, but I heard that I would have better odds trying to combat my heat issues hooking my light directly to the ventilation without anything in the room.

#3). Give up and give all of my money to dispensaries for the medicine I need.

Buy the A.C.

Most people have this problem because they do not understand the importance of a "Sealed" room.

Buy a portable AC unit and install at the lowest point closest to your plants and vent the AC out of the room with a 4"-6" Flanged hole that you put into a wall, opposite of the door.

Then, cut another 4"-6" flanged hole into the top of your door, and install an exaust fan DIRECTLY to it. Keep the door closed at all times.

Your cold air needs to come in at the lowest point, while the hot hair is exausted from the highest point while being as far away from eachother as possible.

The importance of a controlled intake and a proper exaust falls under the importance of a SEALED room. You can put 20 fans in there, wouldn't make a difference if the air is not being controllably exausted out.

The cold air needs to come in at the lowest point while the hot air exits at the highest point, while making sure they are at opposite ends of eachother.

Your HID should also be taking cool air from outside and exausting right out as well. Make sure of this as I have seen 1000w HPS cool to the touch after being properly exausted for 12 hours.

SouthCross said:

Buy the A.C.

Click to expand...

Do you happen to have any kind of a recommendation when it comes to A/C units and a flowering room of my size, 4'x4'x6'?

DocktaGreenThumb said:

Most people have this problem because they do not understand the importance of a "Sealed" room.

Buy a portable AC unit and install at the lowest point closest to your plants and vent the AC out of the room with a 4"-6" Flanged hole that you put into a wall, opposite of the door.

Then, cut another 4"-6" flanged hole into the top of your door, and install an exaust fan DIRECTLY to it. Keep the door closed at all times.

Your cold air needs to come in at the lowest point, while the hot hair is exausted from the highest point while being as far away from eachother as possible.

The importance of a controlled intake and a proper exaust falls under the importance of a SEALED room. You can put 20 fans in there, wouldn't make a difference if the air is not being controllably exausted out.

The cold air needs to come in at the lowest point while the hot air exits at the highest point, while making sure they are at opposite ends of eachother.

Click to expand...

I already have flanged holes in my lower and upper points in the room, but I'll likely have to add another one for an a/c unit, which apparently has to be ventilated correctly as well.

I was talking with a buddy of mine about my situation, and when I mentioned getting an air conditioner he looked at me like I was crazy and tried urging me to upgrade my fans. Would getting a 600+ CFM rated fan make a difference in the room temp when I cannot even get the room cooled down with the box fan in the door?

I don't see how this is difficult. If you have excessive heat you either need to vent it or seal the room and run AC. Nothing else will help. Expect to run 5-10f hotter than whatever the intake air is with just ventilation.

Passive intake down low, exhaust port up high. You need cross ventilation, just a fan in the doorway isn't going to help much. 4x4x6 is 96 cuft. General recommendations are to do a full room air exchange every 3-5 mins. A 4" inline would work fine, though I'd run a 6" and run it on a speed controller turned down.

I'd bet that if you ran your exhaust outside the house you'd see improvement quickly, i had a buddy long ago that was hard headed about exhausting outside, he kept on insisting his problems were nutes, lights, ac, air pump, etc. I kept telling him exhaust outside the room. He never listened, all his shit is dust in the wind now

I have an out door building sealed rooms, not always, but for several yrs to now. I dont purposely vent to the outside or bring fresh air in anymore.
I have massive scrubbers, quality ac,dehuey, c02 generator, high/low limit controllers/atmosphere controller. I dont suffer the outdoor temps/humidity, I never head mites in/out/vent/sealed , no plant deaths or cloning/seedling/flowering issues. I use a few 1k lights, a lg t5.
my door is open when I enter and exit, and I've left it open while working in there too, or when my little dog wants to visit. nothing on schedule, every few days maybe work in the room, sometimes door is open.
every issue I had in the grow room prior was cured with my seal up. If I ever have issues I will try different things, but until then...Ima keep on doing what I've always done=I love the results I get

WeedFreak78 said:

I don't see how this is difficult. If you have excessive heat you either need to vent it or seal the room and run AC. Nothing else will help. Expect to run 5-10f hotter than whatever the intake air is with just ventilation.

Passive intake down low, exhaust port up high. You need cross ventilation, just a fan in the doorway isn't going to help much. 4x4x6 is 96 cuft. General recommendations are to do a full room air exchange every 3-5 mins. A 4" inline would work fine, though I'd run a 6" and run it on a speed controller turned down.

Click to expand...

Should I always expect to run 5-10F hotter when just using ventilation in general, or is my ventilation simply not enough to do what I need to achieve? I had two holes put into my room for ventilation, one lower and one higher, much like you mentioned, however I was told to stop air exchange in the room, and run some ducting to enclose my light for air cooling to reduce the temperature in the room. I also moved my ballast and other small heat generating things out of my flowering room as well.

Before I had my ventilation hooked up to my light fixture, I tried using both my fans to just exchange the air in the room, but it wasn't enough and it seems like the temperatures are reduced a bit more by ventilating the light instead of the air in the room. You can actually see this from the first picture I posted, the ducting runs up the side of my room from the air intake and up to the light, through the light fixture, and back out of the flowering room via the exhaust hole behind the light.

dirtWeevil said:

I'd bet that if you ran your exhaust outside the house you'd see improvement quickly, i had a buddy long ago that was hard headed about exhausting outside, he kept on insisting his problems were nutes, lights, ac, air pump, etc. I kept telling him exhaust outside the room. He never listened, all his shit is dust in the wind now

Click to expand...

I don't see how I would be seeing any kind of improvement by adding more ducting and fans simply to push the air outside. My basement is completely enclosed and there are no windows to the outside, so it would require a great deal of ducting. I have gauged the temperatures where I exhaust back into the basement, and the heat coming out of the room was not enough to change the basement temperatures. I do bring in air from a different section of my basement, and I do have a thermometer where my air comes in and it's always at 72F. When I am exhausting the hot air back into the basement, the thermometer there is reading roughly ~73-74F

chemphlegm said:

I have an out door building sealed rooms, not always, but for several yrs to now. I dont purposely vent to the outside or bring fresh air in anymore.
I have massive scrubbers, quality ac,dehuey, c02 generator, high/low limit controllers/atmosphere controller. I dont suffer the outdoor temps/humidity, I never head mites in/out/vent/sealed , no plant deaths or cloning/seedling/flowering issues. I use a few 1k lights, a lg t5.
my door is open when I enter and exit, and I've left it open while working in there too, or when my little dog wants to visit. nothing on schedule, every few days maybe work in the room, sometimes door is open.
every issue I had in the grow room prior was cured with my seal up. If I ever have issues I will try different things, but until then...Ima keep on doing what I've always done=I love the results I get

Click to expand...

I had a fellow who built grow rooms "professionally", tell me that I do not need fresh air intake and to simply fix my heat issues by using my air ventilation to cool my light. Well, I hooked that up to my light fixture and now I'm just warming up my flowering room with ambient temperatures from my fixture. Everyone keeps telling me that it's possible with just ventilation, but in all honesty I am not seeing this be a possibility for me.

Venting hot air into the same room is the problem. The higher the ambient temp in your basement the harder it will be to cool the flower room.

I had the same problem. It's like trying to cool down hot water with warm water. It takes much more warm water to dispel the heat than it would with cold water.

Or for example: say you have a gallon of water that is 90f. You want to cool it to 80f. So you dump in 2 gallons of 75f water. The temp of the 90f water drops to 85f say. So add another gallon on 75f water to that and finally you reach the 80f you needed. 3 gals to cool 1 gal.

But 1 gal of 60f water would have brought your 1 gal of 90f water right down to 80f.

Air works the same. To cool your hot flower room with warm air it will take a ton of air movement.

You need to get that hot air outside.

Or buy an a/c unit.

also its not all about air temp but also content, unless you got it down like chemphlegm with air scrubbers and the like you are recycling the same air over and over. If you can't vent to the outside either move your grow or do like chem and buy the equipment to seal your grow completely. If i had the cash to spare id seal mine in a minute especially since i live in one of the hottest most humid sections of the country lol

AC vented outside can work but you already have heat problems and portable AC's create a lot of heat if not vented out of the room. If you can't vent the AC don't bother with it, you could end up with even higher temps.

If you had proper exhaust (high up) vented outside (not into the basement), then a high cfm inline on a variable controller for active intake (as low as you can go), you could use the cooler air in the basement combined with your exhaust to manage temps. When using air exchange the combination of exhaust + cooler incoming air will drop your temps. It's a matter of getting enough cooler air coming in to make a difference + exhausting the warmer air up high, typically exhausting at a lower cfm than your incoming air.

I run 700w in a 4x9x7' room with 4" inline fans for exhaust and incoming fresh air, mid summer I'm still able to maintain temps ~80F max. I'm running LED's in there now but I was running 2x 315w Sun Systems for a couple of years with hoods but no venting on the hoods, just the air exchange setup I described above. During warmer weather I'm running the incoming air full tilt and exhaust at 1/2 on my variable controllers, that generates enough cooler air coming in to cool the air in the room. If I run the opposite (incoming at 1/2 and exhaust at full) my temps go up.

JohnCee said:

I had a fellow who built grow rooms "professionally", tell me that I do not need fresh air intake and to simply fix my heat issues by using my air ventilation to cool my light. Well, I hooked that up to my light fixture and now I'm just warming up my flowering room with ambient temperatures from my fixture. Everyone keeps telling me that it's possible with just ventilation, but in all honesty I am not seeing this be a possibility for me.

Click to expand...

I cant comment really, nothing was bliss until I did what I said I did and sealed it up. plants would die in there without c02 though. and with c02 running they would die too unless an air conditioner is employed, and mold would flourish for the excess humidity unless a dehuey is employed.

JohnCee said:

Should I always expect to run 5-10F hotter when just using ventilation in general, or is my ventilation simply not enough to do what I need to achieve? I had two holes put into my room for ventilation, one lower and one higher, much like you mentioned, however I was told to stop air exchange in the room, and run some ducting to enclose my light for air cooling to reduce the temperature in the room. I also moved my ballast and other small heat generating things out of my flowering room as well.

Before I had my ventilation hooked up to my light fixture, I tried using both my fans to just exchange the air in the room, but it wasn't enough and it seems like the temperatures are reduced a bit more by ventilating the light instead of the air in the room. You can actually see this from the first picture I posted, the ducting runs up the side of my room from the air intake and up to the light, through the light fixture, and back out of the flowering room via the exhaust hole behind the light.



I don't see how I would be seeing any kind of improvement by adding more ducting and fans simply to push the air outside. My basement is completely enclosed and there are no windows to the outside, so it would require a great deal of ducting. I have gauged the temperatures where I exhaust back into the basement, and the heat coming out of the room was not enough to change the basement temperatures. I do bring in air from a different section of my basement, and I do have a thermometer where my air comes in and it's always at 72F. When I am exhausting the hot air back into the basement, the thermometer there is reading roughly ~73-74F



I had a fellow who built grow rooms "professionally", tell me that I do not need fresh air intake and to simply fix my heat issues by using my air ventilation to cool my light. Well, I hooked that up to my light fixture and now I'm just warming up my flowering room with ambient temperatures from my fixture. Everyone keeps telling me that it's possible with just ventilation, but in all honesty I am not seeing this be a possibility for me.

Click to expand...

With the room closed up the way it is, there's still residual heat from the light that just collects. Try taking the intake tube off the light so you're sucking fresh air into the room, then using the room air to cool the light. You'll need a carbon filter to flower if smell is an issue. If that doesn't work, you'll need to vent the lights and room separately, which is what I recommend to do anyway. There's going to be heat buildup in a closed basement no matter what, mostly in summer, but I think it should be fine with the 315. Do you leave the basement open to vent the heat out?

You could try a 'swamp cooler'. Get a good sized medium or large igloo cooler, look on utube for some examples of what I'm taking about. Cut the hole on the lid, but don't use a fan, get a roof soil stack (sewer) gasket vent at Lowes or Home Depot. I also use a PVC elbow pipe attached to this vent. Run your exhaust though the swamp cooler. Fill the cooler regularly with ice, it will cool the exhaust and cool the area up to 10-15 degrees.

I don't use loose ice. I bought about 8 gallon jugs of Hawian Punch ($1.50-$2.00) a jug. They are the perfect size, have a top handle to carry them and the juice is good to drink. Filled each of them with water, 4 frozen ones in the cooler and 4 in the freezer getting frozen. I swap them out once a day and have had great results. I only need mine about 5 months out of the year but it's a simple cheap (one time investment) solution. I can post a pic of mine if your interested.

Here are some pics. Exhaust into the left side, cold air out the elbow pvc on the right. Forgot to mention the pvc connection pipe (short one) goes into the rubber gasket on the left to attach you fan exhaust tube to. I use the standard dryer vent flex hose. I had to disconnect mine to move it get the pics. The other pics is of the jugs I use.

Do you like breathing the same stale regurgitated air in sealed environments such as busses, stores, airplanes ect? Neither do your plants. The " buddy" you are listening to is confusing you it seems. To me and I may be wrong but opinions are like assholes and they all stink.... Your room is too hot period. Sealed system isnt working for YOU .
Friends advice sucks.
Be pro active and do some venting.
Yes, you need to.
Honestly asking not being a jerk. Is money a problem? Motivation issues? Dont feel well? Illegal where you are? Why are you continuing in this same direction hoping for different results?

Ive done wot fish explained when their is NO outher way to vent OUTSIDE. ............and as explained an ac would NOT work as the portable ones create higher than normal air out the back of it........ice is the only way u will succeed imo....

JohnCee said:

#1). Air conditioning. I could get a smaller (portable?) air conditioning unit, which has a thermometer built-in that can maintain the temperature by starting and stopping when needed. I am a bit concerned with this route as it's more expensive, and will need to be running to cool the area down. My thoughts are that since the room does not have air circulation that it will have to run less often to keep the flowering room cooled down

#2). Add actual ventilation for the room air exchange, and simply not the light reflector, which means I would need to purchase two additional fans for proper air exchange. There was ventilation for the actual room air, but I heard that I would have better odds trying to combat my heat issues hooking my light directly to the ventilation without anything in the room.

#3). Give up and give all of my money to dispensaries for the medicine I need.

Click to expand...

#2 with fan speed controllers will be the best option so long as you are able to draw to and from the house or out side. It's a low cost investment compared to the alternatives because it will regulate/save heating bills during lights off while adding co2 lights on.

Other than that you may look into sealed co2 but it's rocket science stuff.


I'd personally want some fresh air down there entirely for my own safety. You don't know what you don't know kinda thing.