We are honored to have recently been named a 2018 Green Lease Leader by the Institute for Market Transformation (IMT) and the U.S. Department of Energy's (DOE) Better Buildings Alliance. The award, presented at the 2018 BOMA International Annual Conference & Expo, reflects our deep commitment to sustainability leadership and environmental performance in our data centres worldwide.
The 2018 Green Lease Leaders who were recognized at the 2018 BOMA International Annual Conference & Expo
We are the first global data centre REIT to adapt green lease standards for use in data centres. While common in the office sector, common green lease standards have not traditionally been utilized in the data centre industry. We are changing this. Our actions are helping evolve our industry, enabling mutually beneficial arrangements between building owners and tenants that align the costs and benefits of energy and resource efficiency investments by both parties to improve PUE (power usage effectiveness) and reduce operating costs.
Our use of green leases provides tools to address the split incentive problem that has traditionally limited the adoption of energy efficiency improvements and renewable energy procurement in facilities where the building owner and tenants share responsibility for aspects of the facility's energy use. We have seen strong adoption from our customers who are eager to work collaboratively to reduce operating costs and support more sustainable data centres. Resources and expertise from the IMT and BOMA have supported the successful development of our green lease standards.
As our sustainability efforts continue to gain global attention, we remain strongly committed to looking at ways to increase the sustainable performance of our operations. Digital Realty remains one of the largest buyers of renewable energy amongst data centre providers and has more certified green buildings than any other data centre provider. We doubled renewable energy use between 2014 and 2016, and we are continuing to expand our contracts to supply new renewables to meet our customers' clean power goals. We were the largest participant in the U.S. DOE's Better Buildings Challenge and we exceeded our 20 percent energy efficiency target ahead of timetable. We also executed the data centre industry's first green bond, a nearly half-billion-dollar issuance earmarked exclusively for green projects.
Again, we are very proud to be named a 2018 Green Lease Leader, recognizing our efforts to bring green leasing standards to the unique operating profiles, energy needs and sustainability opportunities of data centres. This is another way Digital Realty is unlocking sustainability value for our customers and our business, and it's an honour to receive this recognition.