My dog opens doors

Since we moved to Fairfax we've had a new luxury not found in our old neighborhood - a fenced backyard. When we lived in Winchester we had one of these, and it was quite nice and large for a small townhouse (we had the end unit, so that definitely helped). The major difference here is that in Winchester we had no dog, and now we do, so the fenced backyard comes in quite handy when the dog wants to go out, but nobody else does.
Don't get me wrong - we walk the dog. We put him on the leash and take him out around the block and around the neighborhood in general (and on very nice days where there's nothing else going on we take him around the lake out back). It is a nice option to have though, the backyard, when one doesn't have the time or the energy to take the dog out for a decent walk.
Ben has been quite content with the back yard. There are a couple of bush-type things, a couple of trees, a nice brick patio area with a walkway out to the gate and some grassy spots on either side. Ample room for a medium-sized Shar Pei to do his business and jump around like a horse when he so chooses. Generally, when he's had enough of the business, or the running and jumping, or barking at whatever walks past the other side of the fence, he just sits down by the door and waits for us to come and open it up. I guess at some point he decided he'd had quite enough of this sitting and waiting and wanted to take matters in to his own hands - or paws as the case might be.
Back in the spring, we had to put Ben out back for quite some time while we had a bunch of kids over for Josh's birthday. Ben is just fine and dandy with us, and with the general visitor, but he tends to disrespect kids (because he was severely disrespected by the children of his previous owner), so we feel it's best to avoid any sort of "incident" and just ban him from things like birthday parties. It was on this occasion that he put his nails, and then foot, and then leg, and then head, and then entire body through our sliding screen door. From what I've garnered, replacing the screen isn't the most difficult thing in the world to do - so no harm, no foul on the dog's end.
Fast forward to August (I'm pretty sure it was August). I was doing some laundry and Ben came down with me and this is generally the time that I let him out back and then go to see if he's ready to come back in as soon as I'm done. I must've been side tracked and forgot about him because about 10 minutes later I noticed a ruckus of sorts coming from the basement. I went down to find the door wide open and Ben jumping around like a horse in the rec room. I found this quite odd, but figured he'd jumped up on the door and accidentally flipped the lever to open the door. It occurred to me at that point that the door was quite perfect for a dog to open without even really trying. I shut the door, apologized to Ben and got on with my day. The next day, Ben went out back again and within 5 minutes he was standing in the living room. At this point I decided it was no longer an accident - the dog knew precisely how to open the door, and would no longer stand for extended waits on the patio.