Kale addiction is a serious problem. Kale is also a gateway vegetable that leads directly to spinach and arugula abuse.

Having it in a greenhouse doesn't increase the sun, which is required for new growth. You may be able to do something like that if you cut it back all the way NOW (although I'd recommend just harvesting all the leaves, as each leaf node will produce new shoots. If you cut the whole thing back you eliminate all the leaf nodes.) - there'd be enough weeks of sun left for new growth - but much better to just harvest mature leaves a few at a time all fall/winter, leaving the youngest, and watch it bounce back and start producing again in the early spring, when no one else has anything to eat from their garden.

But whatever you do, it won't put on new growth from October-March. Which is fine, if you've grown it big enough before then to allow you to pick off leaves a few at a time all winter.

I'll do some experimenting . . . cut some back, cover some up with the greenhouse gizmo and cover some with hay. If I get anything out of it I'm sure it will beat grocery store kale.