; and (B) non-binding guidelines for energy-efficient building design. (2) Targets The voluntary programs described in paragraph (1) shall be designed— (A) to achieve substantial energy savings compared to the model building energy codes; and (B) to achieve these savings up to 3 to 6 years in advance. (g) Studies (1) GAO study (A) The Comptroller General of the United States shall conduct a study of the impacts of updating the national model building energy codes for residential and commercial buildings. In conducting the study, the Comptroller General shall consider and report, at a minimum— (i) the actual energy consumption savings stemming from updated energy codes compared to the energy consumption savings predicted during code development; (ii) the actual consumer cost savings stemming from updated energy codes compared to predicted consumer cost savings; and (iii) an accounting of expenditures of the Federal funds under each program authorized by the title or by amendments made by this title. (B) Report to Congress Not later than 3 years after the date of enactment of the Energy Savings and Building Efficiency Act of 2017 , the Comptroller General of the United States shall submit a report to the Committee on Energy and Natural Resources of the Senate and the Committee on Energy and Commerce of the House of Representatives including the study findings and conclusions. (2) Feasibility study The Secretary, in consultation with building science experts from the National Laboratories and institutions of higher education, designers and builders of energy-efficient residential and commercial buildings, code officials, and other stakeholders, shall undertake a study of the feasibility, impact, economics, and merit of— (A) code improvements that would require that buildings be designed, sited, and constructed in a manner that makes the buildings more adaptable in the future to become zero-net-energy after initial construction, as advances are achieved in energy-saving technologies