Hard Numbers
One of the most current and most referenced studies was performed in 2003 for CaliforniaÂ’s Sustainable Building Task Force, a group of more than 40 California state government agencies. The report, The Costs and Financial Benefits of Green Buildings, of which Kats is the lead author, examines existing data surrounding the costs and financial benefits of 33 LEED-certified projects in California as compared to conventional designs for those buildings.
Cost data in the report, the first of its kind to fully aggregate the costs and benefits of green buildings, focuses on 25 office buildings and eight school buildings with actual or projected dates of completion between 1995 and 2004. The projects were selected because “relatively solid cost data for both actual green design and conventional design was available for the same building” based on modeling and detailed cost estimates.
In the report, Kats notes that virtually no data for conventional buildings has been collected to determine what the building would cost as a green building. And, most green buildings do not have data on what the building would have cost as a conventional building.
The eight LEED Bronze buildings had an average cost premium of less than 1 percent. The eighteen Silver buildings averaged a 2.1-percent cost premium, while the six Gold buildings had an average premium of 1.8 percent. The single Platinum building was at 6.5 percent.
The report concludes that the average premium for all 33 studied green buildings is slightly less than 2 percent ($3 to $5 per square foot).
Another study, Costing Green: A Comprehensive Cost Database and Budgeting Methodology, July 2004, by Lisa Fay Matthiessen and Peter Morris of Davis Langdon, Santa Monica, CA, notes that the cost per square foot for buildings seeking basic LEED certification - not the Bronze, Silver, Gold, or Platinum levels - falls into the existing range of costs for buildings of a similar program type. “The costs are relatively insignificant compared to the benefits that will be accrued by the occupants of the building,” Wille notes.
Kats agrees: “More and more buildings can be built at the LEED-certified level for little or no cost premium. You can easily get at least half-way to certified at a zero-cost premium.”