Ok, well I'm one of those bad guys I guess. Because I deny people on a daily basis for that exact same reason. I do it in a very nice way, but they still get spitting mad. Then they start complaining to anyone within earshot and exaggerating about the whole thing.

Dogs are pack animals. Putting a dog in a backyard/garage because it is hyper is not a good idea. Why not try agility or something similar to work off some energy and get some training in at the same time? Why not take the dog through obedience so you can learn how to relate to and work with the dog? Why not make your dog a part of the family before bringing in another dog to throw in the backyard? If you have behavioral issues with the current dog, adding another dog is the last thing you need to do at this point. You need to fix the hyperness first.

If you interact with your dog daily, providing mental and physical stimulation and training, he will not be too hyper to be inside.

I hope you don't think I'm being harsh, but I really don't think you are realizing that the shelter workers care about the dog's well-being.