I think you have to be very clear on the performance requirements you want. You have to have measures by which you can force that performance or change the lease. So I would say that the lease should certainly have in it what I would call output factors.
I think a second thing that you would want is the ability to vacate that space, or portions of it, some percentage. For example, in the deal that England had, which was called the PRIME deal, I think they were allowed to vacate up to 35%, and it was something like 10% a year. In other words, you would want the ability to be able to move.
A third factor you may want to look at is a way in which you gain some benefit from the cost savings because you are the tenant. If tenants turn off their lights, they should get some benefit. So you may want to look at factors by which the efficiencies and the cost savings don't just go to the landlord but also go to the tenant.