my grow room is way too hot!!!

Hi All,

This is my first posting on this forum so i hope i give enough detail for you to be able to answer my question. Firstly a general thank you to all forum members as the discussion boards on this site ahve really helped me out in the past!

Right i'm on my first grow in about 3 years. i'm also using a pre-made cabinet utilising the DWC method. I'm going to try to put pictures up to help explain where i can.

Basically for security purposes the cabinet is in a built in wardrobe under the stairs - to be clear - i'm growing in the cabinet (with metal doors that shut) and said cabinet is in the built in wardrobe. There is about a metre of space to the left of cab. A quick run down of the setup - 600w HPS light with cool tube (attahced to an extractor fan) positioned in the top left corner. ducting connects to the cool tube. a small intake fan about 2 foot up on the bottom left side. then my resevoir (8 plants), aerator stone for bubbles and a manual desk fan just to circulate the air.

The plants have been in about 2 weeks now from cuttings (3 inch tall) and are now 19-20" tall. The general colouring is excellent, nice deep green. all looks healthy and happy.

THE BIG PROBLEM IS . . . . . HEAT!!!

It has been between 85-95 pretty much the whole time, i've added a 'home made' CO2 kit (yeast, sugar and water) as researched suggests that will help a bit. The exhaust fan is on as high as possible as is the intake fan. Now i'm asking for a lot here, in fact something that may not exist but my question is - how do i cool my grow cabinet down bearing in mind the following restrictions;
- i cannot cut into the metal (nor do i want too cos the smell)
- i cannot move the cabinet
- there is no space for an ac unit inside, plus i think this would get too hot anyway??

i have an idea about putting an ac unit inside the wardrobe (not the cabinet) and hope that would reduce the temperature sufficiently in there and also give the intake fan some cold air to take in the grow room? good idea or dumb ass?


I would also appreciate any general comments about how my girls are looking!

Thanks a million in advance!!

Happy Toking!

Put frozen water jugs in front of your intake fan. This requires changing them everyday however it would cool the room down.

reduce your ambient temp

OK, some questions for you:

1. Where are you exhausting to...is it the wardrobe?

2. How many CFMs is your exhaust fan...is it over 250CFM?

3. Where are you measuring the temp at?

4. Do you know what your water temp is?

5. Is that a CLEAR reservoir that you're using?

Busch97 said:

OK, some questions for you:

1. Where are you exhausting to...is it the wardrobe?

2. How many CFMs is your exhaust fan...is it over 250CFM?

3. Where are you measuring the temp at?

4. Do you know what your water temp is?

5. Is that a CLEAR reservoir that you're using?

Click to expand...

Hi Busch,

1. yeah, the exhaust has ducting attached to the outside of the unit which feeds into a carbon filter, this is for odour control.

2. if i'm perfectly honest i'm not sure. it was pre-built into the unit and didn't have any paperwork etc with it with that information on.

3. the temp is being measured near the top of the resevoir, i.e. base of plant level.

4. the water temp is around about 65 degrees, doesn't seem to go up or down 10 degrees from that.

5. it is clear plastic if that's what you mean?

Thanks for your interest.

lc0278906 said:

Hi Busch,

1. yeah, the exhaust has ducting attached to the outside of the unit which feeds into a carbon filter, this is for odour control.

2. if i'm perfectly honest i'm not sure. it was pre-built into the unit and didn't have any paperwork etc with it with that information on.

3. the temp is being measured near the top of the resevoir, i.e. base of plant level.

4. the water temp is around about 65 degrees, doesn't seem to go up or down 10 degrees from that.

5. it is clear plastic if that's what you mean?

Thanks for your interest.

Click to expand...

OK, first off you need to know that I'm a relative newbie to growing MJ, so take this for what it's worth. So if I've got this straight, you bought a grow cabinet that's pretty much ready to use out of the box (once put together). I'm assuming that the 600-watt light came with the kit, so hopefully the exhaust fan supplied pulls enough air to sufficiently cool the light and cabinet. And you put the cabinet inside a wardrobe (closet), basically a box inside of a box.

The first problem I see is that you're exhausting the hot air into a relatively confined space around the grow cabinet. Basically, you're heating the air around the cabinet, which is also the air that is coming back in through the cabinet inlet...it's essentialy a closed loop. What is the temperature of the air in the wardrobe and near the cabinet inlet?

Ideally, you would want to break the loop, i.e. exhaust the hot air outside the wardrobe (best) or pull the inlet air from outside the wardrobe. Is there any way to run ducting either from the exhaust or inlet of the cabinet to outside of the wardrobe?

If not, then you may have to look into a way to cool the wardrobe air...but even a portable A/C unit generates a lot of heat that has to be vented outside of the area it's cooling.

All that being said, I personally don't think that 85-95* is necessarily going to harm your plants, so long as you can keep your reservoir temps in the low 70's or lower. It's not ideal, of course, but your plants will let you know if they don't like it and your's look good so far in my opinion.

Now for that clear plastic reservoir...that WILL cause you problems in a DWC system, especially if the water temps get much above 70*. If light can get to the water you're going to start growing algae (and some nastier things) in the water. The algae and what not are going to play havoc with your water...ph, O2, and nutrient levels will fluxuate, root rot, etc.

I'd pick up some black duct tape and wrap up that reservoir so that NO light can get in. I'd also cover up any unused holes in the cover.

Busch97 said:

OK, first off you need to know that I'm a relative newbie to growing MJ, so take this for what it's worth. So if I've got this straight, you bought a grow cabinet that's pretty much ready to use out of the box (once put together). I'm assuming that the 600-watt light came with the kit, so hopefully the exhaust fan supplied pulls enough air to sufficiently cool the light and cabinet. And you put the cabinet inside a wardrobe (closet), basically a box inside of a box.

The first problem I see is that you're exhausting the hot air into a relatively confined space around the grow cabinet. Basically, you're heating the air around the cabinet, which is also the air that is coming back in through the cabinet inlet...it's essentialy a closed loop. What is the temperature of the air in the wardrobe and near the cabinet inlet?

Ideally, you would want to break the loop, i.e. exhaust the hot air outside the wardrobe (best) or pull the inlet air from outside the wardrobe. Is there any way to run ducting either from the exhaust or inlet of the cabinet to outside of the wardrobe?

If not, then you may have to look into a way to cool the wardrobe air...but even a portable A/C unit generates a lot of heat that has to be vented outside of the area it's cooling.

All that being said, I personally don't think that 85-95* is necessarily going to harm your plants, so long as you can keep your reservoir temps in the low 70's or lower. It's not ideal, of course, but your plants will let you know if they don't like it and your's look good so far in my opinion.

Now for that clear plastic reservoir...that WILL cause you problems in a DWC system, especially if the water temps get much above 70*. If light can get to the water you're going to start growing algae (and some nastier things) in the water. The algae and what not are going to play havoc with your water...ph, O2, and nutrient levels will fluxuate, root rot, etc.

I'd pick up some black duct tape and wrap up that reservoir so that NO light can get in. I'd also cover up any unused holes in the cover.

Click to expand...

Thanks Busch! I've installed an a/c unit today in the hope that this might work! Seems to be doing ok at the moment! I've done this to try and break the loop! as the exhaust ducting from the a/c is pointed out the wardrobe door and the temp of the wardrobe seems to be cooler, although i haven't taken a reading of that temp yet. the key thing is that with the a/c pointed towards the intake fan the cool air is coming into the cabinet now.

Since my last reply i have also flushed today as i'm moving into flowering period (the plants are 2ft tall now) and need to put in the correct nutes and almost true to your words there was a very noticeable amount of algae growing!! So as you suggested i have put tape all over the holes and around the base of the resevoir!

I'm going to post some more pics soon!

Thanks again!

lc0278906 said:

Thanks Busch! I've installed an a/c unit today in the hope that this might work! Seems to be doing ok at the moment! I've done this to try and break the loop! as the exhaust ducting from the a/c is pointed out the wardrobe door and the temp of the wardrobe seems to be cooler, although i haven't taken a reading of that temp yet. the key thing is that with the a/c pointed towards the intake fan the cool air is coming into the cabinet now.

Since my last reply i have also flushed today as i'm moving into flowering period (the plants are 2ft tall now) and need to put in the correct nutes and almost true to your words there was a very noticeable amount of algae growing!! So as you suggested i have put tape all over the holes and around the base of the resevoir!

I'm going to post some more pics soon!

Thanks again!

Click to expand...

Cool! You may want to put some H2O2 (hydrogen peroxide) or Hygrozime in your res as well...and then do another res change. As the algae dies you're increasing the amount of organic waste floating around, which may cause an increase in bacteria (the bacteria eats the dead organic matter) which may cause the ph to fluxuate dramatically (due to the gasses that the bacteria put out), etc., etc., etc. Best to fix this before it becomes a problem...

It would be much more efficient to just exhaust the air from the cab out of the wardrobe, ac units use a lot of power, and it's basically just transferring heat from one place to another, which a fan will do as long as the ambient temps aren't high.
You don't need to reduce your temps a great deal, an ac unit just seems overkill to me.