TheLEED for Homes Rating System (v4)awards points for theMaterials and Resources (MR) Credit: Environmentally Preferable Productsbased on the use of materials with sustainable attributes, such as concrete with fly ash (a recycled material that reduces the environmental impact of cement production). The scenario indicates that reducing fly ash content in some suspended slab areas due to weather-related curing concerns would cause the project to fall short of the credit’s threshold (e.g., 25%, 50%, or 90% by cost).
According to theLEED Reference Guide for Homes Design and Construction (v4):
MR Credit: Environmentally Preferable Products (1–4 points)
Use products that meet one or more of the following criteria for at least 25%, 50%, or 90% (by cost) of the total materials in the project:
Recycled content: Materials with pre- or post-consumer recycled content, such as fly ash in concrete.The percentage is calculated based on the total cost of qualifying materials across the project.Source: LEED Reference Guide for Homes Design and Construction, v4, Materials and Resources Credit: Environmentally Preferable Products, p. 160.
TheLEED v4.1 Residential BD+Crating system confirms this:
MR Credit: Environmentally Preferable Products
Concrete with fly ash qualifies as an environmentally preferable product if it contributes to the required percentage of material cost. Project teams must ensure compliance across all relevant components.
Source: LEED v4.1 Residential BD+C, Credit Library, accessed via USGBC LEED Online.
The most effective strategy is toignore the engineer’s recommendation and proceed with the original design(Option B). This ensures the project maintains the intended fly ash content to meet the credit threshold. Fly ash typically slows concrete curing, but modern mix designs and admixtures (e.g., accelerators) can mitigate weather-related delays without reducing fly ash content. The LEED AP should collaborate with the structural engineer to explore alternative solutions, such as adjusting the mix or using curing blankets, to maintain both structural integrity and credit compliance.
Why not the other options?
[Reference: LEED Reference Guide for Homes Design and Construction, v4, Introduction, p. 12 (discusses CIR process)., C. Apply for a Regional Priority exemption since the local climate interfered with the project team’s best effort to achieve the point: Regional Priority (RP) credits provide bonus points for addressing local environmental priorities, not exemptions for failing to meet credit requirements. Weather conditions do not justify an exemption for MR credits.Reference: LEED Reference Guide for Homes Design and Construction, v4, Regional Priority Credit, p. 190., D. Demand the project team slow the construction schedule so additional curing time will allow the required amount of fly ash to be used: Slowing the construction schedule is impractical and costly, especially when alternative solutions (e.g., admixtures) can address curing time without compromising fly ash content. This option is less effective than maintaining the original design with adjustments.Reference: LEED Reference Guide for Homes Design and Construction, v4, MR Credit: Environmentally Preferable Products, p. 161 (discusses practical implementation)., TheLEED AP Homes Candidate Handbookemphasizes the need to understand MR credits and practical strategies for compliance, referencing theLEED Reference Guide for Homes Design and Constructionas a key resource. The exam is based onLEED v4, ensuring the relevance of maintaining fly ash content., References:, LEED Reference Guide for Homes Design and Construction, v4, USGBC, Materials and Resources Credit: Environmentally Preferable Products, p. 160–161., LEED v4.1 Residential BD+C, USGBC LEED Credit Library, accessed via LEED Online (https://www.usgbc.org/credits)., LEED AP Homes Candidate Handbook, GBCI, October 2024, p. 12 (references study resources and exam scope based on LEED v4)., USGBC LEED for Homes Rating System (v4), available via USGBC website (https://www.usgbc.org/resources/leed-homes-design-and-construction-v4)., LEED v4.1 for Homes, USGBC, accessed via LEED Online, confirming fly ash criteria., ]
