Dartmouth's campus buildings vary in age from Wentworth and Thornton Halls of the 1820s (the oldest surviving buildings constructed by the college) to new dormitories and mathematics facilities completed in 2006. Most of Dartmouth's buildings are designed in the Georgian colonial architecture style, a theme which has been preserved in recent architectural additions. The College has actively sought to reduce carbon emissions and energy usage on campus, earning it the grade of A- from the Sustainable Endowments Institute on its College Sustainability Report Card 2008.