New ASHRAE Standard to Reduce Heat Island Effect

Requirements to reduce heat and subsequent energy use on building sites are proposed for the green building standard developed by ASHRAE, IES and USGBC.

Five proposed addenda to Standard 189.1-2009, Standard for the Design of High-Performance, Green Buildings Except Low-Rise Residential Buildings, currently are open for public comment. To learn more or to comment, visit www.ashrae.org/publicreviews.

Developed by ASHRAE in conjunction with the Illuminating Engineering Society of North America (IES) and the U.S. Green Building Council (USGBC), the standard provides a long-needed green building foundation for those who strive to design, build and operate green buildings.

Addendum k updates portions of section 5 (Site Sustainability) to improve requirements related to tree-growth rate and adds a mandatory requirement restricting invasive plants. The change extends the tree growth period to 10 years from five years.

"Ten years accounts for a wider diversity of trees across geographic regions to achieve a canopy that provides effective shading," Dennis Stanke, committee chair, said. "The current requirement of five years favors fast-growing trees, which may be more likely to lack stability in storms and to die at a relatively young age."

In addition to addendum k, addendum n is open for public comment until June 20, 2011.

Addendum n improves the heat island reduction provisions in sections 5 (Site Sustainability) to include aged values for solar reflective index and to include a reference to the Cool Roof Rating Council ANSI Standard. It also modifies the solar reflectance and emittance values in Normative Appendix D (Performance Option for Energy Efficiency).

Three addenda are open for public comment until June 5, 2011.

Addendum lupdates portions of section 5 (Site Sustainability), treating porous pavers and open graded aggregate, all of which mitigate the heat island effect, separate from other paving materials. Studies have shown that porous and permeable pavement systems store less energy and therefore less heat when exposed to sun over an extended period of time. The heat is not absorbed and therefore not emitted back into the environment, which results in lower daytime and nighttime temperatures.

Addendum m clarifies condensate collection requirements in Section 6 (Water Use Efficiency), exempting dry climates where little if any condensate would be expected from air-conditioning units.

Addendumo addsa mandatory requirement to section 5.3 (Site Sustainability) to provide pedestrian friendly environments through the use of designated walkways. Vehicles negatively impact the environment through the generation of air pollution, traffic congestion and issues associated with oil extraction and petroleum refining. The use of alternative modes of transportation helps reduce the energy demand for transportation and associated greenhouse gas emissions.

"Requirements for pedestrian friendly environments help encourage transit use and support bicycle mobility, both of which increase physical exercise opportunities and associated health benefits," Stanke said.

Standard 189.1 also serves as jurisdictional compliance option to the International Green Construction Code authored by the International Code Council, ASTM International and the American Institute of Architects.

ASHRAE, founded in 1894, is an international organization of some 50,000 persons. ASHRAE fulfills its mission of advancing heating, ventilation, air conditioning and refrigeration to serve humanity and promote a sustainable world through research, standards writing, publishing and continuing education.