The website background is a 3300sf skylight for Boerner Botanical gardens in Hales Corners, WI designed by BHS Architects, Milwaukee, WI

 

LEED and Wisconsin Solar Design

Wisconsin Solar Design

Wisconsin Solar Design has a long history of environmental work. Beginning in 1981 Wisconsin Solar Design participated in the pursuit of active and passive solar energy applications that had moved into national consciousness as a response to escalating oil prices and concern about polluting the environment. Often referred to as the Camelot period for solar energy usage, this period ended abruptly with the suspension of state and federal incentives for solar use. Wisconsin Solar Design continues its interest in these renewable energy sources providing guidance and assistance to those with similar concerns.

LEED

Leadership in Energy and Environmental Design, LEED Green Building Rating System® is a voluntary, consensus-based national standard for developing high-performance, sustainable buildings. Achieving LEED certified status recognizes the positive environmental intentions and actions of an owner, builder and design team. LEED certified facility users enjoy the long-term benefits of a well-planned, high performance, energy efficient building.

There are several LEED versions intended for different project types. The information cited here is from LEED NC v2.2 (for new construction and major renovations). LEED recognizes achievements and promotes “green” building practices through a comprehensive point-based rating system organized into five major categories. The three categories to which enlightened skylight use may contribute may contribute are 1) Energy & Atmosphere (EA), 2) Materials & Resources (MR) and 3) Indoor Environmental Quality (EQ). These categories are considered below.

Building materials and components cannot in themselves be LEED certified. However, the use of green products in a project can earn points toward LEED certification.

Categories for Rating a Building

I.  Energy & Atmosphere : An energy efficient building can earn from (1-10) points under the “Energy and Atmosphere (EA) Credit Category 1, Optimize Energy Performance” by demonstrating energy savings above the ASHRAE (American Society of Heating, Refrigerating and Air Conditioning Engineers) standard. A proposed building's overall energy consumption is compared to this baseline level using energy simulation software. The points are awarded according to a graduated schedule of energy savings from 10.5% to 42% above the baseline. Credits may be earned as follows:

1) Energy Savings With Skylights. Skylights deliver light to interior areas that are not lit by perimeter glazing thus reducing the need for electric lighting. Modern control systems couple the output of electric lights to available daylight levels automatically dimming or turning off unneeded lights. The resulting energy savings contribute to LEED EA Credit 1.

2) Skylight Design. Solar heat gain and heat loss through radiation, and the impact on heating and cooling energy budgets are considerations in skylight design. Glazing options such as spectrally selective tinted glass, ceramic frit screening and translucent polyvinyl interlayers allow the designer to control the light transmittance and diffusion while rejecting excess heat gain. Low-e coatings and argon gas ensure that modern insulated skylight glass has heat loss (U) values equal to the best window glazing. A thermally isolated frame and insulated sill such as found on WSD skylights is essential to reduce conductive heat transfer. The resulting energy savings contribute to LEED EA Credit 1.

3) Sunspaces Heat Buildings. Passive solar structures can supplement mechanical heating systems and reduce energy consumption. This lowers operating expenses and the energy savings contribute to EA Credit 1.

II.  Materials & Resources: LEED strives to reduce waste in the construction industry and promote recycling. LEED points are available for using recycled materials and additional points are awarded for building materials and products that are extracted and manufactured within a 500 mile radius of the specific job site. Examples of credits earned under this category are:

1) Aluminum Recycling. Re-using aluminum requires only 5% of the electricity consumed to produce virgin aluminum. A recycled content, in this case aluminum, of 10% earns (1) Materials & Resources (MR) point under Credit 4.1. Increasing the recycled content to 20% earns 1 additional point – MR 4.2. The calculations to support these credit points take all of the building materials of a project into account.

The recycled content value of a product is determined by weight. This recycled weight is then multiplied by its cost to determine the recycled content value.

Application to Skylights: Skylight frames are constructed of extruded aluminum parts that are produced to WSD specifications at an extrusion plant. The material is supplied to the extruder as “billet” which is a turned aluminum ingot with very specific alloy and temper characteristics. Skylights also include components such as flashings and closure panels which are made of aluminum sheet metal that has different makeup characteristics from extruded aluminum shapes. Aluminum extrusion billet contains from 0 to 30% recycled content. Sheet metal recycled content is between 30% and 100%.

2) Life Cycle Analysis. An additional positive environmental characteristic of aluminum not specifically addressed by LEED involves the end of aluminum's life cycle. Aluminum scrap and demolition materials are widely recycled due to their economic value.

The durability of a material is an important consideration when assessing its long-term environmental impact. Aluminum framed structures do not rot or rust and are known for extreme longevity. Electricity consumption is significant in producing aluminum, however, the “embodied energy” in aluminum is spent over many years. As a result, aluminum has been referred to as an “energy bank.”

3) WSD and MR Credit 5.1: Regional Materials. 1 LEED point is awarded for the “use of building materials or products that have been extracted, harvested or recovered, as well as manufactured, within 500 miles of the project site for a minimum of 10% (based on cost) of the total materials value.” An additional 1 point is available for raising this total to 20% (MR 5.2).

The point of origin is defined as the site where a product is manufactured. A 500 mile radius drawn around Wisconsin Solar Design's south-central Wisconsin location completely covers 6 states and touches on 3 others as well as portions of Ontario.

4) WSD and MR Credit 7: Certified Wood. WSD manufactures greenhouse plant benches made entirely of South American Ipe wood. This material is available to WSD as Forest Stewardship Council (FSC) certified wood, proof that it is harvested in a sustainable manner.

LEED Materials and Resources Credit 7 awards 1 point for projects that use 50% FSC certified wood throughout. The required calculation is based on the cost of the materials. WSD Ipe plant benches contribute significantly to earning this credit.

III.  Indoor Environmental Quality: Environmental Quality (EQ) Credit Natural daylight has been shown to improve morale and productivity in office buildings, student performance in schools and to promote a feeling of well-being in retail and residential environments LEED recognizes the psychological value of daylight by awarding (1) certification point for day-lit interiors.

WSD and Daylighting: EQ Credit 8.1 requires that 75% of regularly occupied spaces be lit to 25 foot candles by natural means. Skillful use of skylights provides natural light to interior spaces. A variety of glazing materials gives the designer control over light levels.

WSD and LEED

WSD has LEED accredited professional staff available to provide further information on how skylights may contribute points to LEED certification.

Web Links

United States Green Building Council, home of the LEED program. Green building rating systems are available as free downloads. Directory of LEED AP professionals. www.usgbc.org

US Department of Energy, web site for information on energy efficiency and renewable energy technologies. www.eere.energy.gov

Energy Star: Federal Tax Credits for Energy Efficiency www.energystar.gov/taxcredits

Rebates and Tax Credits: DSIRE , The Database of State Incentives for Renewable Energy showing state and local utility rebates and tax incentives www.dsireusa.org

Building Green, publisher of Environmental Building News and Green Spec product guide, subscription based with some free content. http://www.buildinggreen.com