LEED credit requirements offer two options for non-roof areas: Provide any combination of several strategies-shade, paving materials with an SRI of at least 29, and/or an open grid pavement system for 50 percent of the site hardscape. Or, place a minimum of 50 percent of parking spaces under cover.  Any roof used to shade or cover parking must have an SRI of at least 29.

 

Cool paving materials minimize the absorption of solar heat and the subsequent transfer of this heat to the surroundings. One type of cool paving material is a lighter-colored concrete product (manufactured with light-colored cementitious materials and light-colored aggregates) with a high ability to reflect sunlight. Solar reflectance or albedo is a measure of a material's ability to diffusely reflect light from the sun (unlike SRI which incorporates both reflectivity and emissivity). It is expressed on a scale of 0 to 1.0, where an albedo value of 1.0 represents total reflectivity. Light-colored surfaces in shades of white, beige, light gray and terra cotta generally have higher albedos than dark-colored surfaces and therefore help achieve the minimum SRI of 29. Proper maintenance, including washing and resealing, is required to maintain a high albedo level and subsequent SRI value.

A second type of cool paving is porous or permeable pavements, which allow water to filter into the ground, keeping the pavement cool when moist. Compared with asphalt, pervious concrete and grassed grid pavements through evapotranspiration, will reduce surface air temperatures by 2 to 4 °F (1 to 2 °C).

For LEED credit requirements for roofs, options include using concrete roof tiles or cement shingles having a specified SRI (equal to or greater than 78 for a low-sloped roof or 29 for a steep-sloped roof) and a high albedo.
The Portland Cement Association (PCA) found that 135 concretes tested for solar reflectance had an SRI of least 29(Solar Reflectance of Concretes for LEED Sustainable Sites Credit: Heat Island Effect, 2007). All products tested, therefore, met LEED Heat Island Effects requirements for Non-Roof and for steep-sloped roofs in the Roof categories (segmental concrete paving would typically be used on low-slope roofs.) The lowest reflectance values were from concretes composed of dark gray fly ash.

The study reports that solar reflectance of the cement had more effect on the solar reflectance of the concrete than any other constituent material. The solar reflectance of the supplementary cementitious material (fly ash or slag cement) had the second greatest effect. The solar reflectance of the fine aggregate had a small effect, while the solar reflectance of the coarse aggregate had no significant effect.  Surface finishing techniques also have an effect as smoother finishes typically have higher solar reflectance. "With
most concretes having an SRI of at least 29, this is an easy credit to earn that most designers ignore," says building science engineer Medgar Marceau, PE (Illinois), LEED AP, CTL Group. 

Precast concrete pavers with an SRI of at least 29, offer freedom of design with a variety of colors, textures, patterns and sizes. They enable designers to create garden terraces, lunch areas and architectural plaza decks from rooftop spaces that would otherwise be unattractive and inaccessible.

Concrete is the structural system of choice for vegetated roofs because it provides a continuous load-bearing surface. Projects constructed using waterproof concrete made with proprietary admixtures allow for the elimination of membranes, and therefore simplify design, construction and maintenance.

Water Efficiency (WE)

Water Efficient Landscaping (Credit 1.1 Reduce by 50 percent; 1 point. Credit 1.2 No irrigation or No potable water use; 1 point)
Intent:Limit or eliminate the use of potable water, or other natural surface for landscape irrigation.

Innovative Wastewater Technologies (Credit 2; 1 point)
Intent: Reduce generation of wastewater and potable water demand, while increasing the local aquifer recharge.

A growing number of urban projects are capturing runoff and recycling water for irrigation. Concrete pervious, permeable and grid pavement systems with rainwater harvesting systems help contribute points in this category.