(NBBJ) - How much it will cost a grower or vintner to obtain Napa Green certification of sustainability practices depends on the program and certifier.

“The direct costs are minimal,” said Nate Weis, director of winemaking for Silver Oak and Twomey, which have production facilities and vineyards in Napa, Sonoma and Mendocino counties. “But the indirect costs, depending on what is already implemented, can be significant.”

The Duncan family is behind the iconic Silver Oak and Twomey wine brands. The organization has pursued third-party sustainability certification of its holdings through several groups, both known in the wine and construction businesses as well as not yet front of mind for many.

More than a dozen and a half Duncan family sites in those three counties were certified by the California Sustainable Winegrowing Alliance over a number of months. And its Napa Valley facilities also were certified last year under U.S. Green Building Council and Napa Green Winery programs.