This article first appeared on my Green Building Law Update blog. The Green Building Law Update blog is intended for the entire environmental industrial complex (not just lawyers).

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The U.S. Department of Housing and Urban Development and the U.S. Department of Agriculture have determined, effective June 6, 2015, that adoption of the 2009 edition of the International Energy Conservation Code for single family homes and the 2007 edition of the American Society of Heating, Refrigerating and Air-conditioning Engineers 90.1 for multifamily buildings will not negatively affect the affordability and availability of HUD and USDA assisted housing.

You care because this new minimum standard for energy efficiency in housing is widely seen as a benchmark driving green building and impacting significantly more units than LEED.

The two standards apply to different building types: the IECC applies to single family homes and low-rise multifamily buildings (up to three stories), while ASHRAE 90.1 applies to multifamily mid- or high-rise residential buildings (four or more stories)

On April 15, 2014, at 79 FR 21259, HUD and USDA announced in the Federal Register the Department of Energy’s determination that the 2009 IECC and ASHRAE 90.1-2007 standards would improve energy efficiency (and yes, DOE has also already made that determination for the 2015 IECC but HUD and USDA are two versions of the code behind) triggering this second step in the federal government analysis.

For the 34 States and the District of Columbia that have already adopted the 2009 IECC or a stricter code, there will be little or no impact from HUD and USDA’s adoption of this standard, since all housing in these states is already required to meet this standard as a result of state legislation. In the 16 states that haven’t adopted the IECC for single family homes, HUD and USDA announced the average incremental cost of going to the higher standard is $1,019 per unit.

For impacted HUD programs in the 38 states and the District of Columbia that have adopted ASHRAE 90.1-2007 or a higher standard, there will, by default, be no adverse affordability impacts of adopting this standard. For the remaining 12 states that have not yet adopted ASHRAE 90.1-2007, HUD and USDA estimate the incremental cost of ASHRAE 90.1-2007 compliance at under $500 per dwelling unit.

You also care because most significantly this will advance green building because HUD and USDA will accept certifications for a range of energy and green building standards that require energy efficiency levels that meet or exceed the 2009 IECC or ASHRAE 90.1-2007 as evidence of compliance with the standards. These include the ICC-700 National Green Building Standard, Enterprise Green Communities, ENERGY STAR Certified New Homes, ENERGY STAR Multifamily High Rise, LEED-NC, LEED-H, or LEED-H Midrise, and several regional or local green building standards, such as Earthcraft House, Earthcraft Multifamily, Earth Advantage New Homes, or GreenPoint Rated New Homes.

In addition, several states have adopted energy efficiency codes or standards that exceed the efficiency levels of the 2009 IECC and ASHRAE 90.1-2007, including, for example, the Title 24 California Energy Code in California, Focus on Energy in Wisconsin. And the 2015 IECC in Maryland. HUD and USDA will accept certifications of compliance with these state codes or standards as well as other state codes or standards for which credible third-party documentation exists that these exceed the 2009 IECC and ASHRAE 90.1-2007.

For all intents and purposes federally assisted housing must now be green. And while such is generally viewed as positive and as advancing green building (.. the big winner may be LEED), some worry about the implications for affordable housing and others about the homogenization of American housing by federal government efforts to save the planet.