I just brought in my shelves, exact same size & I got a pair of 4 x 4' T5HOs that are more than enough. I'm actually having to adjust the distance to the plants b/c some bright light lovers are going dark purple (like really dark).
I also wrapped 3 sides in a reflective bubble-wrap insulation to keep the temps up a bit. It's called Reflectix I think & can be found at your local HD/Lowes type home improvement store (comes in rolls). Cool stuff, it's not wimpy, real durable actually. Check it out I recommend it if you're looking for some insulation.
May I ask what kind of silver insulation you use around your rack? I'm setting up a similar orchid shelf using the same kind of shelving. The lighting information really helps too.
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I'm not sure what you mean by silver insulation, but if you are looking for a reflective material this might fit the bill. Reflective Mylar
You may want to pick up a pair of sunglasses also.
I'm curious what people think of their new lights and reflective material. Post pictures perhaps? I love my lights - totally changed my orchid growing!