I Need help adjusting conditions…

[Bullmark69]

Hello, I’ve ran this topic up the flagpole before, but have yet to find a suitable solution.
So I’m growing 2 plants in a 2’x6’ space…..running 2 different HLG LEDs, a 320W and a 150W.
I have a 4” exhaust that’s adjustable venting directly outside.
Growing in KokoBop amended with various dry organics. I’ve had pretty good success and usually pull 16-18oz from a run.
Right now it’s HOT outside….temps in the upper 90s and supposed to remain that way for the next 10days or so.
My space is a closet in a small guest cottage that serves as my office. Total space is about 14’x16’ and the only cooling is a window unit AC.
When the temps are really high the AC will only bring the room temps down to 75-77F during the hottest 3-4 hrs of the day. This means the temps in the grow closet can reach 80F or higher easily. The airflow in the closet seems good…,,I’m running a small fan at the base of the plants below the canopy and a larger one blowing across the top of the canopy.
The grow is in week 9 of flower and they look to have another week at least, likely 2. I’m trying to keep my RH below 50%.
My issue is for some reason my leaf surface temps (lst) is higher than the air temps. At this moment the lst is around 82f and the air temp is 79f.
Based on my understanding of the subject, under LEDs, the lst should always be slightly lower than air temps. Based on the VPD chart my plants are over transpiring big time.
I’ve lowered the light intensity. I was hoping this would help lower air temps as well. I usually cut temps back during later flower but I’m handcuffed with my current setup coupled with record highs outside.
I guess I’m wanting to know why the lst is now higher than air temps??? And what, if anything, I can do to regulate things back to a recent VPD??
I’m hesitant to raise the RH a lot, but did increase it to 50% in hopes of slowing down the transpiration.
I can also open the closet door but that makes it warmer in the lung space…..and the poor AC unit is working overtime as is.
I’m afraid I’m losing yield and terps with things out of whack. The buds are nice and frosty but seem a little dry compared to my other grows where I’m not battling record high temps.
Pics are from this morn. Plant on the left is Fruity Pebbles OG, right is Grandi Guava.
Luckily they both look like they can harvested in the same window.
Lemme hear what u guys/gals think on this one…….and any input is greatly appreciated

 

[LoveGrowingIt]

Does your guest cottage have a crawl space below it? I ask because I'm wondering if that could be a source of cool air. It would require some carpentry work, though. Otherwise, it might be better to vent your grow space into the same room as the air conditioner. As it is, you're probably sucking hot air into the cottage from outside, placing a significant burden on the air conditioner. (I'm guessing the air conditioner normally recirculates the air in the room.)

 

[Bullmark69]

Does your guest cottage have a crawl space below it? I ask because I'm wondering if that could be a source of cool air. It would require some carpentry work, though. Otherwise, it might be better to vent your grow space into the same room as the air conditioner. As it is, you're probably sucking hot air into the cottage from outside, placing a significant burden on the air conditioner. (I'm guessing the air conditioner normally recirculates the air in the room.)

no crawl space…..it’s on a concrete slab.
I’m not sure about the performance of the AC unit. I guess it’s just like any other window unit. I have thought about replacing it with a larger one.
What I’m trying to figure out is why my leaf surface temps are higher than the air temp???
What is causing this and how can it be remedied?

 

[LoveGrowingIt]

What I’m trying to figure out is why my leaf surface temps are higher than the air temp???

The heat must be coming from somewhere.

What is causing this and how can it be remedied?

I can't think of any sources of heat other than the light and the ambient air temperature.

I’m hesitant to raise the RH a lot, but did increase it to 50% in hopes of slowing down the transpiration.

Transpiration cools the leaves. Perhaps they're not transpiring enough. Your plants' leaves look like they're not photosynthesizing well. That could be a clue. A problem with low humidity and high heat is the plant may not be able to deliver enough moisture for the whole plant to transpire.