I wouldn't worry about the temps below 60 unless you are getting temps below 50!! My greenhouse can experience temps into the low 50s when the fuse blows and I do not find out about it right away but even my rex begonias seem to do ok with these kinds of dips.
Don't know about the T-40 as I tend to gravitate towards
the specialized bulbs that are designed for plants. These may be either incandescents which generate some heat or generally flourescents, such as Gro-Lux or the like. In fact I had a set up kinda like yours with two lower shelves with gro lux in 4' fixtures. The ballasts tended to add some heat to the area especially since I ran them 14 to 16 hours a day and had foil facing all around the shelf system.
Here is a commercial website that has information on what light is about that might help you. I am not affiliated with it so I am not really recommending buying anything there but you can learn and perhaps find a local store that will sell something comparable in your area-don't forget to check out the pet shops especially if they sell herps (reptiles).

Here is a link that might be useful: Natural Lighting

I'm just wondering whether there is any data showing whether having plants exposed to 20,000fc spread over 24 hours is different from having 20,000fc spread over 12 hours. I ask because I noticed you have lights on at night, resulting in a 24 hour light period, whereas most people I know (including myself) have lights on during the day in addition to natural light, and then darkness at night. I actually don't know for sure which way is better, but you might want to try switching it around (unless you can't due to aesthetic purposes) because I feel like supplemental lighting in addition to natural lighting provides much better light than dilute light spread over 24 hours....but someone can correct me if this is wrong.

I was always under the impression that T5s put out a bucket load of lumsn (4 bulbs for 20,000, I think!) and for a long shelf structure light that, *personally* I prefer tube lighting (I know some will disagree with me!). I have a similar set up and I have both CFLs and tube lighting, and I find it tricky to mount the CFLs, especially on the lower shelves, because the shape of the bulb is akward, so unless you want bulbs and wires trailing everywhere out on the sides of your shelf, you'll have to have your bulbs within the shelf, and that limits you to growing smallish plants (unless your shelf height is really high)...but that's just my experience!

The area under my CFL hood does heat up a little bit, but not much - perhaps 2-4 degrees centigrade? low 50F is probably not a good temperature on the long run for the plants - have you tried a warm mist humidifier, or wrapping bubble wrap/insulation material on the bottoms of the windows? The problem with incandescents/HPS is that I feel like they generate too much heat to have close to the plants (an advantage of CFLS) so in a shelfing system, you would only be able to have this setup on the top tier of your shelf (definitely not in the inner tiers, IMO)

Anyway good luck with that! We have alot of people who have experimented with different lighting systems so I'm sure they will chime in.

Well first of all, How much of that sliding glass door is is unobstructed. If its blocked by shade trees you need more light than if it gets sun for a good part of the day. Also, keep it clean to maximize light transmission. The next thing I recommend is to set your lights to come on in the morning and run all day.About 12 to 16 hours a day depending on the types of orchids and how much natural light they get. The lights will aid the natural sun light this way and the plants will get a much needed darkness period. They like a good 8 hour night to sleep just like we do. Orchids don't like perpetual daylight. As far as the CFLs go The 42w in the 5000K range will serve you just fine. I don't know wht types of Orchids you are growing so I won't suggest how many CFLs you might need, just use yourown judgement and when you think you have enough lights add a couple more just to be sure.

Thank you all for great advice. I got down and checked the bulbs I am currently using, turns out they are 32 watt T-8's. I think they are daylight color bulbs. I will replace them with grow light bulbs- thanks for the link. The reason I was running the lights at night was to save costs on electricity. I am under the assumption that juice costs less at night. As for my sliding glass door, I think it is a great idea for me to insulate the bottom of the glass. Today I removed the summer screen so that should also allow more light into the room.

I don't know what kind of plants you are growing, but four 32 watt t-8's put out enough light to turn phal leaves red at a distance of 8 inches. you could put higher light plants closer. i wouldn't replace them unless you have to.

A kilowatt hour is not like a mobile phone but wouldn't it be nice. :-) It costs the same day and night. You will run into problems exposing your plants to light 24/7. I also would not be impressed with the results of a single overdriven 40 w tube.You will get better results with supps working in tandem with your south window. Most of us on the board use 4 tubes. That has not been quite enough and many of us have added cfl's to tubes. Overdriving may give you a boost but certainly not that significant. If you are simply using supplimental lighting sans window, (for you at night) you would need 3 times the amount of tubes/cfl's to run at night. There have been numerous discussions over the years on this board about light. The discussions were predicated upon the idea of using artificial light in tandem with a window, not alone. Running at night or without a window requires a substantially different amount of lighting. About 3x more than one would use with a window.

If you are concerned about costs, tubes are not nearly as energy efficient as cfl's. If you would like to add heat, 42w cfl's and up will do the trick. Its not necessary to get into the cost of gas lighting. 23w really don't produce significant heat unless you are running numerous. At that point you are better off to invest in 42's or 85's

For shelving it is rather easy to use the larger cfl's. Shot in from the sides if you are also going to use tubes or installed from the front. I have 1 larger shelf that has 2, 42's, an 85w and 4 4watt tubes. My orchid room is 78º day and 60 nights. NO heat vent is open in the orchid room.

Kelvin rating is colour. 5000-6500 is optimal. 23w usually are 2500 and lower, usually around 1700 as I recall. Not really great, very yellow.

There have been numerous discussions about large cfl's and there have been pics posted on these threads. You may want to do a GW search for 85w cfl's and "big bertha 85w cfl" (Our nick name for the 85w cfl). I've used just about everything tubes, grow lights cfl's. The results are absolutely incredible.

Incadescents can be used in tandem with cfl's they would be tough on shelves. The would need to be at a distance of 2' or more. Take a look at this set up, moreover take a look at the plants!:
http://forums2.gardenweb.com/forums/load/orchids/msg1122041017472.html?9

http://forums2.gardenweb.com/forums/load/orchids/msg1008215420604.html

Plant leaves turning red is not a sign of bulb stength. It means that the plant has been under-light. Plants that continually turn red or violet means they are not getting enough light. Phal leaf burn is white

Clara

Clara, thank you for taking the time to respond to my post. I have no excuses for poor results now. Time to buy my plants some lights! Thanks again to all!