The Leonard Academy is in their words a non-profit “think and do tank” that was founded in 1997 to provide a wide range of sustainability services and is based in Madison, WI. Their website is www.leonardacademy.org…
in April of 2008 the organization published a survey of LEED EB building owners to determine how much it costs on a per sq foot basis for each category. They found that there is a wide range of costs across the board and that the median across all types of buildings was $1.58. This number includes all of the hard and soft costs that go into the greening of existing buildings.
Please take a look as the report may help you understand all the expenses that are needed to green existing buildings. The report can be found at:
http://www.leonardoacademy.org/download/Economics%20of%20LEED-EB%2020090222.pdf