It's not the ideal, but it's better than crating him/her for 8 hours without being left out at all, and provided he/she is fully housebroke, can be trusted not to tear up the room, and has water available in that room. It's also much safer IMO than leaving it outside in a fenced in yard. Also, since you'll be coming home to let him/her outside half-way though, I don't think it's too bad at all. Most people do work at least an 8 hour work day, and that doesn't even include travel time back and forth to work. I'm sure that some of those people's dogs ARE crated throughout the day and their owners don't come home 4 hours after starting to let their dog outside at all. You know your dog best and more than we do, of course, so it's your final decision to make, but I do NOT think your idea is cruel.