Energy consumption and production is at the core of virtually all environmental impacts. Focusing on these issues is how Marcus Sheffer has developed a national reputation as a leader in energy management, efficiency, conservation and renewables. After 12 years at the Pennsylvania Energy Office, he founded Energy Opportunities, Inc., and provides technical consulting services on building energy issues, renewable energy systems and the environmental impacts of human enterprises. He also operated the York County Community Foundation Energy Program for 20 years, providing technical assistance to local nonprofits. A teacher and author of the Pennsylvania Solar Manual and co-author of The Integrative Design Guide to Green Building, Marcus has also held numerous volunteer positions with USGBC, ASHRAE and the International Living Future Institute.