The building, under construction at the former base hospital site, will be the first five-star green-rated building in Orange.

The Environmentally Concerned Citizens of Orange have invited ADCO Pty Ltd, which is constructing the building on behalf of Verde, to address Wednesday's meeting upstairs at the Parkview Hotel.

ECCO president Nick King said people were interested in what was required to obtain the rating.

"We're really excited about this building and we're hoping this will provide a benchmark for future constructions," he said.

"The skyline of Orange is increasingly moving up - it's an example of what can be done and hopefully will follow through to residential development."

Green ratings go up to seven stars and the Housing Plus development proposed for Lantana Place is expected to achieve the full rating.

The building is expected to host the Department of Primary Industries, as well as members of the Department of Premier and Cabinet and possibly the Office of Sport.

Everyone is welcome to attend the meeting from 7pm.