I recently lit up a few buildings for an exhibit and I wanted to show how I did it. I'm not sure if I'm the first person to do this, but no one in my LUG had seen this done before.
Step 1. build a roof with a 1-brick cavity (or bigger) to fit your LED lighting product. In this build, I used a flexible single colour LED rope light.
Step 2. Close the roof all around it, covering the parts of the LED lighting that won't be exposed. Then add your 1x2x5 clear bricks.
Step 3. Pop the roof onto your building. (note that in this case, I did a 'green roof' and had to add a little more green to the seems to hide light-leakage.
And that's it. You have fluorescent lighting (there is no other light source in this photo).