SUSTAINABLE STANDARDS - STANDARD 189 PERSPECTIVE

Site & Landscape

Written by R. Kirk Johnson, AIA, LEED AP

As introduced in the August Edition of the North Texas Chapter digital magazine, the fourth edition public draft of the Standard 189.1P Standard for the Design of High-Performance Green Buildings was released in September anticipating a publish date in January 2010.  The standard is a joint partnership between the U.S. Green Building Council (USGBC), the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), and the Illuminating Engineering Society of North America (IESNA) that is designed to significantly move forward sustainable concepts and construction by providing a code-enforceable standard for green buildings that may be adopted by jurisdictions, agencies, clients, rating systems, and regulatory entities.

According to the proposed standard, the regulation is written in code enforceable normative language for ”buildings designed, constructed, and capable of being operated in a manner which increases environmental performance and economic value over time, seeks to establish an indoor environment that supports the health of occupants, and enhances satisfaction and productivity of workers through integration of environmentally-preferable building materials, and water-efficient and energy-efficient systems.”

The regulation is organized around general regulatory protocols and six primary LEED Rating System topics such as Site Sustainability, Water Use Efficiency, Energy Efficiency, Indoor Environmental Quality, Impact on Atmosphere, and Operations.  Within each chapter, five residual categories such as general requirements, compliance paths, mandatory provisions, prescriptive options, and performance options.  In a conceptual sense, the regulation upon adoption contains many code enforceable LEED related items.

This brief overview article concentrates upon information as it relates to the Site Sustainability and exterior Water Use Efficiency portions of the regulation.

MANDATORY OPTIONS

Site related Site Sustainability and Water Use Efficiency categories within the standard discuss the following.

• Site Selection
• Site Development
• Mitigation of Heat Island Effect
• Light Pollution Reduction
• Site Water Use Reduction

SITE SELECTION

Sustainable sites as addressed in the standard must meet all mandatory requirements with an option to provide compliance to either a prescriptive or performance option.  Mandatory requirements for site selection require that development occur with one of the following alternatives.

• Within an existing building envelope.
• On a brownfield site
• On a greyfield site
• On a restricted green field site.

Each of these is discussed within the regulation.  However, the restrictions with greenfield site selections require adherence to limits that may be developed such as proximity to basic community connectivity items, residential density, or planned public transportation access.  Additionally, greenfield sites that are on prime agriculture land, forest land, or park land may only be selected for development if the building purpose is related to the associated use of the land.

SITE DEVELOPMENT ACTIVITY

Within the Standard, site development activity is prohibited in areas lower than 5 ft above the USFEMA 100 year flood level, within 150 ft of any fish or wildlife habitat conservation area, or within 100 feet of any natural wetland.  An exception to this restriction is a low-impact trail that may be developed within 15 feet of the wildlife habitat or natural wetland area.

MITIGATION OF HEAT ISLAND EFFECT

Similar to the LEED Heat Island Reduction credits, site hardscape within the Standard 189, must be covered with at least 50% of the area with materials that reduce the effect of localized heat islands.  Options include providing bio-diverse native plantings, materials with a minimum solar reflectance index value of 29, and buildings or elements that shade the hardscape.

However, one particular item unique to Standard 189 is the requirement for above grade building and retaining walls to be shaded.  Yes, above grade building walls.  Although the building may be rotated up to 45 degrees for calculating compliance, shading may be achieved through the usage of plantings, existing buildings, permanent building projections such as awnings or roof overhangs, and man-made structures and other similar elements.  In this requirement, a minimum of 30% of the east and west above-grade walls and retaining walls must be shaded for a height of 20 feet.  If plantings are used they must be bio-diverse native plantings.  Walls that produce on-site renewable energy are excluded from the requirement.

ROOFS

Standard 189 requires that a minimum of 75% of a roof, whether building or covered parking, be constructed of materials that mitigate heat island effect by providing a minimum solar reflectance value or by providing a roof compliant with the Energy Star program.  The minimum solar reflectance value is the same requirement as contained in the LEED Rating System.  Roofs that are used as thermal energy collectors, rainwater harvesting, or green roofs are exempt from the requirement.

REDUCTION OF LIGHT POLLUTION

Another area contained in the Standard 189 Sustainable Site section pertains to the reduction of light pollution into the atmosphere from within the property and building.  Under this section, the total installed initial luminosity of the site lighting must be less that the total site lumen limit.  Additionally lighting must comply with maximum allowable backlight, uplight, and glare restrictions for luminaries.  Light trespass limits are required at the property line and maximum vertical luminance levels.

SITE WATER USE REDUCTION

All sites within Standard 189 are required to provide a minimum of 60% of the improved landscape area with bio-diverse native or adaptive plantings.  Irrigation systems require hydrozoning to water plantings in typology methodologies and must be arranged in such a manner that sprinklers do not spray water directly on the building or within 3 ft of a building.  Irrigation systems require smart controllers utilizing evapotranspiration and weather data.

PRESCRIPTIVE OPTIONS

In addition to the mandatory requirements for site selection, site development, heat island reduction, and light pollution listed above, Standard 189 also requires the usage of either a prescriptive or performance based compliance method.  The prescriptive method listed for site development requires compliance with two particular requirements.  One requires that a site development effectively provide a minimum of 40% of the entire site with pervious materials such as vegetated plantings, vegetated roofs, porous pavers, or similar permeable materials.  Buildings constructed on a brownfield site are exempt or if 50% of the projected annual rainfall is captured and reused on site.  The second prescriptive requirement requires that Greenfield sites provide a minimum of 20% vegetated area consisting of native plants or adaptive plants.

Landscape areas may be irrigated with a maximum of 30% potable water.  

PERFORMANCE OPTIONS

The alternative to meeting the prescriptive option listed previously is to provide a performance compliant option.  In this scenario, the project development must meet performative criteria that can be substantiated with calculations.  Three requirements listed below must be met with this option.

• Projects within an existing building envelope must manage a minimum of 20% of the average annual rainfall on the development footprint through infiltration, reuse, or evapotranspiration.
• Projects on a greyfield or brownfield site must manage a minimum of 40% of the average annual rainfall on the development footprint through infiltration, reuse, or evapotranspiration.
• Projects on all other sites must manage a minimum of 50% of the average annual rainfall on the development footprint through infiltration, reuse, or evapotranspiration.

Site water use reduction in the performance option requires that consumption for the irrigation not exceed 35% of the baseline evapotranspiration for the area compared with a baseline of 70% ETo for turfgrass areas and 55% for all other plant material.

WHERE TO GO FROM HERE

At this point in time, public draft four of the Standard 189 is currently requesting final comments through November 2, 2009.  The stated goal is to publish the standard around the first of next year.  After final publication, it will be up to individual jurisdictions whether to adopt the standard and the timeframe for adoption.  If the decision is to implement the new standard, it may be adopted independently of current codes as a high performance building option, used additively to current codes, or adopted by some other measures.  Additionally, the relationship of the standard to existing or future LEED Rating Systems has not been released nor has the relationship to future versions of ASHRAE 90.1.

However, it is safe to say that the standard upon adoption will open up many more avenues for sustainable construction than prior to the release of the standard.  It will set a new benchmark for sustainable site excellence in the industry.