creative heat control- ideas?

[rangerjake]

I got my tent set up in an attached garage. My climate is a moderately humid one with mostly temperate weather in the summer (75-80 usual high temps, 55-60 usual lows). I have found so far that the grow tent is getting a bit warmer than I like- upper 80s when it is at it's hottest- on the warmest days we have seen so far (mid 70s). I have taken some basic mitigation steps to cut down on the ambient heat in the space, using black cloth over windows to darken the area and reduce solar radiation, cycling lights off for 4 hours during the warmest hours (2-6pm). My next step is to cut back to an 18/6 and have lights off from 1pm-7pm. I would really like to keep the tent temps 85 and below, and I don't need a dramatic change to do that- frankly most average days I think 85 will be my high. But we will see heat waves and a dozen days in the 90s for sure.

I am running CMH lights, 2 x 315 in a 5x5. I have an Active Air exhaust fan pulling roughly 400cfm on high. Though this is more about the temp in the space around the tent, rather than in the tent.

I am not going through the expense and work to set up a CO2 system to make the heat more plant friendly. I am loathe to invest hundreds of dollars in a portable A/C unit to cool the garage 10 degrees. But that may be the only route to achieve my goal.

My questions are the following:

-how detrimental is it to plants to spend 4 hrs a day, 3 days per week (that is a broad average) at 85-90 degree temps?
-has anyone devised a minor temperature mitigation strategy that I could feasibly employ?

[alltatup]

Hi jake, Here's the deal: too much heat during flowering will stress plants: I had one hermie during flowering due to excess heat, which is how I learned my lesson. Also, too much heat isn't good for terpenes... And too much humidity can really mess up your grow--mildew, etc. So heat and humidity control are super-important during the flowering phase. https://www.growweedeasy.com/5-secre...s-heat-control

That being said, I'm a hydro grower; if you're a soil grower, you don't have to worry about root temps the way I do.

I always say that this ain't no cheap hobby. I've had to invest in this and that to fine-tune my grow environment (spare bedroom): a 50 pint dehumidifier that sits in the doorway of the room so that the warm air blows out into the hall; I switched from HPS bulbs to LED COBs for a 50% reduction in heat in the room; I keep the ceiling fan on all the time for good air circulation. This is where we have to get creative in order to balance what we can afford with what we need to do in order to grow the best bud we can:

Can you insulate your grow room?
Come up with a creative way to draw cooler air into the room and exhaust warmer air out? Good air circulation is crucial.

[rangerjake]

I am a coco grower right now. The heat is intermittent. It has been rare to get above 85, typically so far 72-82 with some outlier temps hotter and colder. I think moving the tent location/tent size is going to be the play as the autos get towards flowering and before the photos switch over.

[mmmaxGROWman]

Hi Jake,
I have noticed a 2 to 5 degree temp drop when I added a good inline fan to bring fresh air in through a lower port on my tent. I also dont use a carbon scrubber for max air flow, I just slip a carbon sock that filters air but does not ruduce air flow. Hope this helps you.

[rangerjake]

This is a good idea! I also do not use a carbon filter, so nothing to be gained on that front.

[9fingerleafs]

i grow outside with 85-90 temp during the day but the humidity stays above 75%, plants may grow a bit slower on the hottest days but as long as they got big roots with enough moisture plants will thrive

[rangerjake]

Yeah- I am being overly cautious. I am sure lots of people grow with great success in higher heat extremes than I deal with. Humidity has been kept mostly in check so far between 35-60%

[Scarletwhitewidow]

i dont really understand why need a portable ac ,you can use the ac outlet sourcing the lights.and put a fan in garage .

[HappyDaze]

If you can keep your root zone cool, they'll be fine. I'd put some panda film on the bottom of the tent and put the pots right down on the floor. The concrete is going to be quite cool, and the white reflective film will ensure that any radiated heat from your lamps isn't warming up the surface. And like mmmMax said...in through the bottom, out through the top, and situating your ducting to pull the heat right off the lamps is optimal.

Keep posting, I'm interested to see how you do. I went with a LED lamp instead of a ceramic, primarily because I wasn't sure how to manage temps in a tent. I have always used HPS lamps in cool tubes in bigger spaces.

Cheers

[rangerjake]

This idea is the most creative idea for incremental cooling. This is my first indoor grow and I was hopeful with the CMH being cooler than HPS that it would be markedly so. But it has really been less the lamps temp that is the problem and more so the ambient garage temp in the heat of the day climbing up to the mid-upper 80s. Hard to keep things cooler in the tent when surrounded by that temp.

[Toker1]

Why not run the lights at night? Take advantage of the coolest part of the day.

[Toker1]

To cut back on heat in the summer I veg with 12 on, 5.5 off, 1 on, and 5.5 off repeat. The one hour of light breaking up the dark cycle keeps them in veg.

[rangerjake]

That's what I have been doing. So far lights have been out from 2pm to 6pm. I am changing that to 1pm to 7pm to mitigate a little more. Also intrigued by the light cycle you run in summer (12-5.5-1-5.5). Is that functional for autos and photos? First I have heard about that style.

[Toker1]

It’s for photos, autos will be in veg/bloom based on how old they are. So light schedule is not as detrimental to keep them in veg.
Yeah, that’s what I use. Check out the gas lantern technique for more info in the light schedule I suggested.

https://balancemmc.com/index.php/2016/11/05/gas-lantern-routine-growing-cannabis/

[rangerjake]

Thanks for all the ideas everyone. Here's where my head is at:

I think fighting to keep that tent cooler in that garage is a fools battle unless I plan on sinking heavy coin into stupid things. Luckily I have other indoor spaces that I can utilize and I can sink money into other more useful things to make those spaces work. Thinking of downsizing the 5x5 tent into 2 2x4 tents, each with 1 315 CMH. This way the tents are more modular and can go into below grade basement if needed where it is plenty cool. I can continue to vent with one fan, just need to get a Y piece to run ducting to each tent. So tent investment needed. I have a small spare room to use if not the basement as well, and that can be outfitted with a small window mount A/C if need be. All of that seems the most versatile and modular. Also has applications beyond just rectifying this situation. I will update on the grow journal as changes get made- probably in the coming couple weeks before the autos start to turn the corner.

[alltatup]

It's good that you have alternative spaces to consider for your grow room. Garage would also be harder to keep warm in the winter (if you have any kind of a winter where you live). I'll be very interested in seeing what you come up with, and look forward to some pictures!! This is the most fun hobby I've ever had, and puttering around in the grow room each day has become a very important part of my routine. ;-}

[Toker1]

I build my garden room inside my garage. Have 3 tents running inside it year round. Keeping it cool in the summer is always an issue, but I run an evaporative cooler (a swamp cooler). Works well, keeps my temps upper 70’s in summer. Sometimes hits lower 80’s on the hotter ones.
Only issue is swamp coolers will not work in high humidity locations (won’t work in Florida for example).

[mmmaxGROWman]

Sounds good Jake, that garage seemed like a hard place to control temps. My first grow was in a spare baths Jacuzzi tub! Cover it with plywood and went to town. Now I'm in tents with led lights.and I really enjoy them.
The garage seemed like a challenge, so much easier on an enclosed ac controled environment. Good growing