LEED V4 – How Green Roof Contribute & Changes from Previous LEED V3
Green roofs continue to contribute to the heat island effect credit in LEED v4. However, in v4, the credit now offers 2 compliance approaches.
Option 1 – (worth two points) now requires a combination of roof and nonroof measures.
So for option 1 – a combination of site measures/0.5 + reflective roof area/0.75+ green roof area/0.75 must be greater than the total site paving and roof area.
This is now a weighted area calculation, so 1000 sf of green roof / 0.75 = 1,333.33 sf of compliant area.
The bigger kicker is that site paving is included – it is all or nothing, so if you have a 10,000 sf green roof (13,333 sf weighted), and a 10,000 sf asphalt parking lot, you will not earn any credits.
Option 2 – Parking under cover (1 point)
Place a minimum of 75% of parking spaces under cover. Any roof used to shade or cover parking must (1) have a three-year aged SRI of at least 32 (if three-year aged value information is not available, use materials with an initial SRI of at least 39 at installation), (2) be a vegetated roof, or (3) be covered by energy generation systems, such as solar thermal collectors, photovoltaics, and wind turbines.
So for option 2, if parking spaces are under cover with a vegetated roof covering 75% of the structure, the project can earn 1 point. http://www.usgbc.org/node/2613950?return=/credits
Green roofs also contribute to the new credit Rainwater Management. 2 points or 3 points are available for sites that manage on site the runoff from the developed site for the 95th or 98th percentile of regional or local rainfall events using low-impact development (LID)and green infrastructure.
Green roofs will contribute to onsite runoff management and will help earn points under this credit. A comprehensive stormwater runoff calculation will need to be prepared, and the depth of the green roof will need to be known so you can identify how much stormwater the system will hold in a typical rainfall event. http://www.usgbc.org/node/2764291?return=/credits
SSc3 – Open Space
Similar to the old credit, sites that provide outdoor space of at least 30% earn 1 point (of that 30%, 25% must be vegetated). Outdoor space must be physically accessible – green roofs count if projects that achieve a density of 1.5 floor-area ratio (FAR), and are physically accessible, extensive or intensive vegetated roofs can be used toward the minimum 25% vegetation requirement, and qualifying roof-based physically accessible paving areas can be used toward credit compliance.
SSc2 – Site Development- Protect or Restore Habitat
2 points are available for projects at project from development activity 40% of the greenfield area of a site AND restore 30% of the site that was previsoulsy disturbed with native or adapted vegetation. Projects that achieve a density of 1.5 floor-area ratio may include vegetated roof surfaces in this calculation if the plants are native or adapted, provide habitat, and promote biodiversity.
New for v4, projects must either not require irrigation, or demonstrate a 30% reduction from a calculated baseline. Using a green roof system with native/adapted plants that do not require irrigation will help with this prerequisite. Furthermore, no required irrigation also earns 2 points, and a 50% reduction earns 1 point.
Energy and Atmosphere
Green Roofs will also help with EAp2/c1 like with the old system, but the standard is now ASHRAE 90.1-2010.
Innovation and Design
Language can remain the same
Materials and Resources
Calculations are done completely differently in v4 – and fall across multiple credits. The first is Building Product Disclosure – EPD – which would require you to have a third party Environmental Product Declaration – which I’m guessing you might not have.
The second option is Building Product Disclosure – Sourcing of Raw materials. Option 2 under this credit is what you are most likely to comply with, though perhaps you can work with the manufacturer to get the public disclosures required by Option 1
Option 1 (1 point)
Use at least 20 different permanently installed products from at least five different manufacturers that have publicly released a report from their raw material suppliers which include raw material supplier extraction locations, a commitment to long-term ecologically responsible land use, a commitment to reducing environmental harms from extraction and/or manufacturing processes, and a commitment to meeting applicable standards or programs voluntarily that address responsible sourcing criteria.
- Products sourced from manufacturers with self-declared reports are valued as one half (1/2) of a product for credit achievement.
- Third-party verified corporate sustainability reports (CSR) which include environmental impacts of extraction operations and activities associated with the manufacturer’s product and the product’s supply chain, are valued as one whole product for credit achievement calculation. Acceptable CSR frameworks include the following:
- Global Reporting Initiative (GRI) Sustainability Report
- Organisation for Economic Co-operation and Development (OECD) Guidelines for Multinational Enterprises
- N. Global Compact:Communication of Progress
- ISO 26000:2010 Guidance on Social Responsibility
- USGBC approved program:Other USGBC approved programs meeting the CSR criteria.
Option 2. Leadership extraction practices (1 point)
Use products that meet at least one of the responsible extraction criteria below for at least 25%, by cost, of the total value of permanently installed building products in the project.
- Extended producer responsibility. Products purchased from a manufacturer (producer) that participates in an extended producer responsibilityprogram or is directly responsible for extended producer responsibility. Products meeting extended producer responsibility criteria are valued at 50% of their cost for the purposes of credit achievement calculation.
- Bio-based materials. Bio-based products must meet the Sustainable Agriculture Network’s Sustainable Agriculture Standard. Bio-based raw materials must be tested using ASTM Test Method D6866 and be legally harvested, as defined by the exporting and receiving country. Exclude hide products, such as leather and other animal skin material. Products meeting bio-based materials criteria are valued at 100% of their cost for the purposes of credit achievement calculation.
- Wood products. Wood products must be certified by the Forest Stewardship Council or USGBC-approved equivalent. Products meeting woodproducts criteria are valued at 100% of their cost for the purposes of credit achievement calculation.
- Materials reuse. Reuse includes salvaged, refurbished, or reused products. Products meeting materials reuse criteria are valued at 100% of their cost for the purposes of credit achievement calculation.
- Recycled content. Recycled content is the sum of postconsumer recycled contentplus one-half the preconsumer recycled content, based on cost. Products meeting recycled content criteria are valued at 100% of their cost for the purposes of credit achievement calculation.
- USGBC approved program. Other USGBC approved programs meeting leadership extraction criteria.
For credit achievement calculation, products sourced (extracted, manufactured, and purchased) within 100 miles (160 km) of the project site are valued at 200% of their base contributing cost. For credit achievement calculation, the base contributing cost of individual products compliant with multiple responsible extraction criteria is not permitted to exceed 100% its total actual cost (before regional multipliers) and double counting of single product components compliant with multiple responsible extraction criteria is not permitted and in no case is a product permitted to contribute more than 200% of its total actual cost.