Establishes a green building code and authorizes the mayor to adopt regulations. Regulations (20 D.C. Mun. Regs. 3518, 3521) set building energy performance compliance pathways and establish that a building owner may not, in the process of complying with the energy performance requirements, "implement a measure that poses a threat to the health and safety of a building occupant or user, including by reducing indoor environmental quality."

Establishes that a license is required to operate a child development facility and authorizes the Mayor to promulgate minimum standards for operation of licensed facilities. Municipal regulations (5-A D.C. Mun. Regs. 122--129) establishing health and safety standards for licensed child development facilities require licensees to "ensure that the Facility is free of moisture, mold, and mildew, including but not limited to, moisture resulting from water leakage or seepage" and maintain floors free from dampness. The facility health and safety standards also address, among other things, lead-based paint, ventilation, space heaters, pest control, use of non-toxic materials and equipment, and carbon monoxide alarms.

Requires landlords to remediate mold contamination in rental dwellings and to disclose previous mold contamination to prospective tenants. Regulations (14 D.C. Mun. Regs. 4111) require landlords to maintain for three years information known or that should have been known about the presence of indoor mold contamination, unless the mold has been remediated by a professional. Directs the District Department of the Environment to establish minimum work practices and guidelines for mold assessment and remediation and to set a threshold level of indoor mold contamination that requires professional remediation. Also requires the Department to establish a licensing program for mold professionals, along with minimum mold work practice standards and guidelines, and prohibits anyone from engaging in the business of mold assessment or remediation without being certified or licensed. Regulations (20 D.C. Mun. Regs. 3200 et seq.) establish a licensing program, and provide guidelines for mold assessment and remediation below the threshold requiring licensing. Public housing tenants must be given notice of their rights to receive an inspection and remediation of mold under this law through the Public Housing Resident Bill of Rights, mandated under separate legislation (D.C. Code § 6-232).

Requires sellers of property containing up to four dwelling units to provide to purchasers a real property disclosure statement on a form approved by the Mayor. Regulation adopting Seller's Disclosure Statement (17 D.C. Mun. Regs. 2708) requires information about sellers' knowledge of environmental problems on the property, including radon, asbestos, lead-based paint, and formaldehyde, and the presence of carbon monoxide detectors.

Prohibits persons or companies from conducting radon screening, testing or mitigation unless they have been listed as proficient by the U.S. EPA or have received certification of proficiency from an organization approved by the Mayor. Requires the Mayor to maintain a public list of those who have been listed as proficient by EPA. Authorizes the Mayor to issue rules establishing radon screening, testing, or mitigation programs in the District that are in compliance with any recommendations or guidelines published by EPA. Regulations adopted by the Department of Energy and Environment (20 D.C. Mun. Regs. 3250) require persons conducting or offering to conduct radon screening, testing, or mitigation for a fee to be certified as proficient by the National Radon Proficiency Program or the National Radon Safety Board.