Northwestern University:

Northwestern requires that all new buildings be LEED-certified. Silverman Hall on the Evanston campus was awarded Gold LEED Certification in 2010; Wieboldt Hall on the Chicago campus was awarded Gold LEED Certification in 2007, and the Ford Motor Company Engineering Design Center on the Evanston campus was awarded Silver LEED Certification in 2006. New construction and renovation projects will be designed to provide at least a 20% improvement over energy code requirements where technically feasible. The university also released at the beginning of the 2008–09 academic year the Evanston Campus Framework Plan, which outlines plans for future development of the Evanston Campus. The plan not only emphasizes the sustainable construction of buildings, but also discusses improving transportation by optimizing pedestrian and bicycle access. Northwestern has had a comprehensive recycling program in place since 1990. Annually more than 1,500 tons are recycled at Northwestern, which represents 30% of the waste produced on campus. Additionally, all landscape waste at the university is composted.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". What percentage of improvement over energy code requirements will be the goal of all new construction and renovations?
at least a 20%