That's only 32 watts/sq ft. Although the enclosure does provide side reflectance, most of the light will bounce multiple times before it reaches the leaf surface. Every time it bounces, it loses light energy to heat. Particularly if the fluorescents have reflectors, ventilation is not automatic and may not be sufficient.

Tomatoes need a lot of light, and if they have that, will soon fill up the entire terrarium.

What is your method for discarding the run-off water? If you simply add fertilized water, the water will evaporate before the fertilizer is used up. Thus leading to a build-up of fertilizers. If you add plain water, and rely upon leftover fertilizer, the fertilizer will not be optimum because some elements will be used disproportionately to their presence in the fertilizer, leading to a build-up of rejected elements. Also waste products would accumulate.

Lermer - I'm listening, and glad that you replied. The ventilation fans are mounted in the top, and are controlled by a thermostat.
Do you think the lights would do better if I removed the foil tape from the inner walls?
Also, I'm gonna construct some type of catch basin in the bottom of the enclosure, and will drain the excess water to the outside.

EG

This sounds kind of like my idea I had and might try. I'm going to have two 4 foot two bulb fixtures side by side and I may attach wood or something on the ends just to make them an even 2 feet wide. Anyway, I will then wrap and hang white reflective material from the fixtures and just let it hang via Velcro about 3 feet. This way with the material hanging from the fixtures I can raise/lower as needed and can raise the lights as much as 3 feet then. But man Id love to get one of those Hydrohuts and deck that thing out in some nice fluorescents standing upright or something.

Good luck with your project. If you do get it set up successfully you will have to post some pics and stuff. Id be very interested.

Crazy8 - I have a garden blog that I put all of the pictures on. The project is split up into 4 different posts, and parts 1 and 2 are already posted. If you would like to follow my project, feel free to drop by, and click on the category "building projects" on the right side of the page to see the first 2 parts with photos. I'll be posting part 3 tomorrow. You can click on each photo to make them bigger. Take care.

EG

Here is a link that might be useful: EG's Blog

Hey thanks a lot cannabis. I got it bookmarked now so I will be paying attention.

Lermer - I would like to get you to look at this photo, and tell me if you think the reflective tape will hurt my light distribution. I have 2 exhaust fans mounted above the lights. I will grow vegetable seedlings in there.

BTW- anyone's input would be greatly appreciated, as I know absolutely nothing about growing under lights.

EG

Here is a link that might be useful:

These things look very well constructed. It would be interesting to see the results you guys get from these grow boxes. I have a camo lunch type bag my dad just gave me last week from something. Well it has a milar (or maybe it actually is milar)interior. Well ever since I got it I have been eyeballing it having a few ideas run through my head. Like maybe when my peppers germinate and are ready for soil I could put on in a small cup then put it inside the bag and place it directly under my light and see how well it works.

Not considering it to be a permanent technique, just something to do to see what happens.:D
Maybe I will post a pic and you can see what I am talking about.

Generally I recommend white paint instead of specular aluminum. Because white diffuses the light and allows infra-red heat to pass through, while aluminum foil reflects and retains the infra-red, and reflects specularly creating hot spots.

If you had a large grow operation, I would consider infra-red/heat blankets, at $250 for 4' x 100'. This would stealth your room from infra-red detection. The hot air exhaust could heat the rest of the house, thus avoiding a heat bloom leaving the chimney in summertime.

If you want light from the side, I recommend mounting lights (such as fluorescents) from the side. If you keep the lights within an inch of the leaf surface, you really don't need reflective surfaces on the side. The plants will grow leafs where the light is. You would have more air movement without the terrarium.

Lermer - ok, for my intended application.....in your opinion, would my plants do better with the inside painted white - versus the foil tape that I have installed? I'm only going to grow my own transplants for my garden, nothing more.

EG

Given the limitations of your question, white would be better than specular aluminum. However if you bring the lights closer to the plants, you will have more light (because of less reflective losses) and more ventilation (because the terrarium limits external ventilation). What are you trying to accomplish with the terrarium?

What if you got some of that white reflective material? Wouldn't that work better than paint? I got 100 sq.ft. of that stuff for only $15. Also I noticed the fans that were being used, wouldn't it help for over all air circulation and temp control to use some slightly bigger fans? Maybe its just me. Perhaps run a test with a thermometer and seal up the box and turn the fan and lights on and see how hot it gets.

You both will have to post up some results. Im very interested in seeing between you both what kind of results you get with these.

What are you trying to accomplish with the terrarium?
I'm sorry for not giving all of the details earlier. So, here goes.
I don't have room in my house to grow seedlings, and my cats ruined everything I tried last year in the little windowsill greenhouses. So, my only option is to grow my seedlings in my shed out back, which is not heated. I felt that I could take this small enclosure, and easily provide the plants with anything that they need...warmth, cooling, ventilation, and light. The lights will be lowered to within 1" of the top of the plants, and adjusted accordingly as they grow upward. I can insulate the outside of it, provide more fans for ventilation, or incorporate a small heating source if necessary. Sometimes, in my opinion...smaller is better, and more cost effective. So, I hope to grow strong, healthy seedlings for my own use, that's all. My feelings were - these two lights confined to a smaller area would be more effective, than under normal conditions. And, for the time of year that this will be tried, if the reflective foil tape will create more heat, it would actually be a good thing.

Crazy8 - These fans move alot more air than you probably think. I'm not going to get all scientific about psychrometric properties of air or anything - but if the proper number of air changes per hour, or minute can be achieved - it should work...no matter what size fan you use. Of course, keeping the temperature of the enclosure down to a desired level by means of ventilation is an issue to be considered, as well.
White reflective material is something that I have not thought of. I'll check into that. Thanks. I intend on doing some temperature testing this coming weekend.

I'd like to thank the both of you for your input so far, it is greatly appreciated.

EG

If it helps anymore here is a link to a local shop I get my stuff from. Im not trying to plug them because even though I shop there, its only because they are the only shop close to home like what they have. Anyway the link to the reflective material is here http://www.brewngrow.com/items.jsp?category=20 Hope this helps.
Also as far as temps go since you have good fans (Ill take your word for it since you know what your talking about;) maybe if it does get to hot, rather than adding fans just use a dremel or something and just make some vent holes since heat rises.

Well, keep us posted.

Crazy8 - thanks for the link. As you probably figured out, I do things much differently than most folks....but usually my crazy ideas work very well. Most people that drive by my house probably think that I have a meth lab in the back or something. I'm always building something weird. LOL. Although I am a master of several skilled trades, I know very little about growing seedlings under lights. So, I came here to learn from those that have the answers to the questions that I seek.

EG

Lermer is correct about your choice of reflective material, foils actually do quite a poor job. You can spring for mylar, though if you do I would recommend avoiding actual "Mylar" because it is a Dupont patent and is artificially expensive. You can get something called metalized polyester film that is exactly the same at about 1/3 the price. In honesty though, for small spaces such as yours, paints work nearly just as well. Normal white house paint is fine as long as it is flat, but I would recommend something called elastomeric paint. It is used for roofing, its almost like a liquid rubber and can be purchased in a white color by the gallon. It is an extremely efficient reflector and does a good job of reflecting all forms of radiation. If you haven't found a solution already I would recommend that. Also, there is a way of getting more light energy from long florescent tubes where you want it. Get foil tape (2" wide for T12 floros, 1" wide for T8s and make sure it has a clear adhesive) and very carefully stick it on the back side of your florescent tube which faces away from your plants and towards your reflector, directly on the bulb, be sure to avoid folds bubbles and wrinkles. Make sure the tape falls an inch or two short of the end caps as the bulb is hottest here and you definitely don't want the metal tape to create a short between the usually metal caps. If you got the tape on there nice and straight with a minimum of imperfections they will be noticeably brighter on the side facing your plants. This works by reflecting the photons directly back out the front side of the bulb instead of them coming out of the backside, hitting whatever reflector you have and then making their way back down to the plants. The trick to a successful florescent grow is to keep the distance that the light has to travel as short as possible and this technique minimizes that distance by several inches. I hope this helps and happy gardening!

hautions - that is a very interesting concept, foil tape on top side of the bulbs....I may try that. Although it has been a while since I posted....I actually have my lighting system propagating seedlings right now, for the early 2009 season cole crop. It's doing pretty good so far, but I feel that i'll be needing more light for tomatoes later. Before trying the tomatoes in March, i'll definitely remove the foil tape from the sides, and paint the interior walss with a flat white paint. I'll be posting current photos of my seedlings tomorrow on my blog, if you want to drop by and have a look. Thanks!

EG

Here is a link that might be useful: EG's garden blog