question about light and heat
 

Awhile back, electricians installed T5 lights in the room I plan to grow my orchids in this fall and winter. My plants are now outside on my backporch, as they have been all summer. I know it won't be too long before the weather at night will be too cool for them, so I'll have to move them in. With your help here on OB, I was able to determine the approx. correct distance the lights should be positioned above my orchids, but now I'm concerned about the heat in the room. I know that as the temp. drops outside, the room will become cooler, as well....but....I would like to move my orchids inside sooner than necessary if possible because I've had a few issues this summer with the wind blowing some off of the shelves on the porch (as recent as the last few days). I haven't monitored the temp. in the room at night yet, but I have for the day: Yesterday, the temp. outside was about 85 degrees most of the day, generally speaking...and inside the grow room, it was about from 90-95 degrees according to the thermometer. That's not preferable for some of my orchids, but that's another issue than what concerns me most at this time. It is the temp. between the lights and the two shelves (especially the upper one). Using that upper shelf as an example, the height between the lights and it is approx. 26" and the light fc is approx. 1600. I understand that approx amount of light would work fair for my Phals (maybe a lil too much, but not greatly). ?? Measuring about 1/2 way between the two (approx. 13") yesterday with a spot temp gauge, I measured about 104-105 degrees....that's terrible....no way could I put orchids there. Do you think I have misunderstood because I didn't think the T5s heat output was that high. By the way, I had a humidifier and fan on at the time, too.

I would appreciate your thoughts and advice.
Thanks in advance,
Vicki

They definately give off more heat than I anticipated before putting them in last fall as well. The fixture alone provided the majority of the heat for my room last winter and the small electric heater that was frequently on the winter before just sat there monitoring the temp (automatic thermostat). You may have to reconsider your configuration? Since heat rises, can you change your layout to place all your plants BELOW the fixtures? Also additional air movement above what you have provided in the past may be necessary?

t5 lamps run at 95 degrees F. So with no outside venting, your room could, theoretically get to 95F. I temper this by opening basement windows (mine are in a basement) and letting cold air in at night. I also run several fans to try to dispell the warm air. Other than that, I have no suggestions. It's still better than the "hot" HID lamps.

My grow room has an East exposure picture window. I have 2 banks of T-5's 4 bulbs in each on each side of the room. I run a ceiling fan, have the air conditioner vent open and run a small humidifyer for 60% humidity. I also have one of those inexpensive column type ocsillating floor fans if it's really intense heat that I can turn on in the a.m.> I live in Florida where its hot anyway and my plants are thriving and blooming. In the winter I turn the vent off for any furnace heat and get a nice temp difference...the room actually gets cool. Your plants will adapt if you try to improve the conditions for them.

thank you
 

Thanks everyone...Mayres, Ross and Vanessa. I always appreciate your help.

I'm still trying to understand the details better. May I ask another question, please? Is there a chance that a constant "less than suggested fc" of artificial light (14 hrs., in my case) equal a greater amount of natural light for less hours? (Does that make sense?? Hmm, I know there is a much simplier and a much better way to ask this question, but I can't think now what it is) I'm sure you understand what I'm trying to ask, though ?? I'm sorry.....it's late.) I'm wondering because: I had to move some things around in my new grow room, so now all of my orchids are together on 1 shelf about 3' under the t5s...all getting the same amount of light (which is only about 500 fc) until I can figure out if there's something I can do to give each particular type (my catts, phals, etc.) the amount each needs. I checked the leaves with my spot temp. meter earlier tonight, and it registered approx. 85-90 degrees, so I don't think I should move the lights any closer to the plants or else they would burn.

Thanks again,
Vicki

I move plants closer to my T5's that need more light by using various heights of cardboard boxes. You should be able to get as close as you want - the heat is generated from the ballast that is on top of the lamps and the heat rises.

mayres
 

Thanks for your help, Mayres.....positioning cardboard boxes closer to the light source to obtain correct lighting for each plant is a good idea, but I'm wondering if your lights are the same as mine because moving any of my orchids closer than they are now would burn the leaves ?? Mine are high intensity....54 watts per bulb (216 watts per fixture). I have 2 fixtures....here is the link: Hydrofarm - Hydrofarm FLT54GH4 Four Foot Commercial 4-Tube T5 Fixture . Any ideas? You or anyone?
Thanks again,
Vicki

Vicki, this is how I have mine set up. The Phals are around the perimeter of my grow table. My Paphs are closer to each end of the lights (thei lights get dimmer on the ends. My Catts and highlight chids are nearing the middle under the lights. My lights are suspended on stands on each table. I can lower them with the pully type mechanism that came with the stands. The lights are 21/22 inches above the bottom of the tables. I freaked out that I would cook them at first but they have acclimated quite nicely. My cooler growing chids are near windows in other parts of my house.

Yes I do believe orchids "bank" light. My dendros on my lanai never get the recommended duration or footcandles that the orchid books claim they need. So with that in mind I think it applies to indoor lighting as well. Good luck with your new grow room! :)

Vanessa
 

Thanks for your reply, Vanessa. I read your post this afternoon, and I've been working with my orchids and their new home since then...trying to see what I could come up with (actually, trying to copy you). I got a little braver after reading that you have your lights placed 21-22" from your plants, so I moved mine closer, too. Not quite 21-22" closer yet, but I'll get there. I've just got to get up a lil more nerve cuz I'm not quite past that "scared-of-burning-my-orchids" thing yet. lol

I've been trying to visualize your setup from what you said in another post and this one, too.....sounds like you have a nice grow area.

I feel better about them "banking" light, as you said. I seriously doubt that I could ever provide as many fc as recommended for any of my orchids with this set-up. After I realized that I didn't get as much light as I had hoped for from the lights I bought, I had thought about maybe adding supplemental lighting, but my prayers every night still include getting a greenhouse someday. lol
Thanks again,
Vicki