If your goal is to reduce the heat load inside the greenhouse, the shade cloth should be on the outside.

We drilled holes through the ridge and wired the "shade" to it. Since the north half is shaded by the foiled bubble wrap insulation, we didn't need to do both sides. It reaches 105F so no plants can spend the summer in it.

I thought it would be easier to put the shade on the outside, although I have 2 windows and I'm wondering if the shade will effect that. Has anyone ever cut their shade to make it easier to open them. I'm just concerned with fraying.

What kind of shade cloth is it? Knitted or Woven? Knitted will not fray if cut and woven will. As far as putting it on the inside or outside.... Although many people put their shade on the inside and it works great and is way easier on maintenence, the fact is that the suns rays are already inside the greenhouse once it hits the shade, for that reason, it is better go on the outside.

I haven't purchased it yet. I'm trying to determine whether I should buy just a black shade or go with aluminet. I would assume you can't cut that.

If you put it on the inside, it should last a lot longer and remain much cleaner because it won't be subjected to wind, rain, bird crap, and leaf deposits. If it's on the outside, it will look like your GH has a tarp hanging on it...if appearance is a concern for you or your neighbors. I have mine draped on the inside and prefer that. Here's a picture of my nearly finished GH showing the arrangement of the shade cloth.

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It sure LOOKS better on the inside.

I think if you decide to put it on the inside, it needs to be white.

Whether you choose inside or outside, I would stay away from dark colored shade fabric.
Try to stay as light colored as possible.