A building doesn’t have to be new to be efficient. Today’s leading building owners are retrofitting buildings, converting existing buildings into models of sustainability. Building energy retrofits are investments in efficient technology during building renovation. While most building owners still pursue single technology improvements, market leaders bundle together energy saving technologies to get deeper savings in a more comprehensive approach. Energy performance contracting is one business model that enables building owners to implement whole building retrofits and significantly lower energy consumption and operating costs. Essentially, the upgrades are paid for through energy savings over time. Photo credit: Jack Amick/Flickr.