OK, well, the original question was about "recycling" your own resources when taking down your own building. I don't think there is any recovery of cost in this case.
Too bad: assume you defined a building (selected the place but did not yet start actually building it) but it is accidentally in the wrong place and you want to "move" it, i.e. destroy it and rebuild it at another place. In this case I believe the invest for the first selected site is lost. Right?
Also if you conquer an enemy building and then destroy it, there is no benefit except that your enemy does not have this building anymore.
A little recycling bonus would be nice in both cases...