To determine a decarbonization target for the project, carbon reduction measures can be applied to scenarios. C.Scale highlights salient carbon reduction measures that can be consistently modeled with available data. The set of carbon reduction measures included in C.Scale do not represent an exhaustive list of possible emission reduction strategies.
Reuse
Building Reuse
The percentage of existing building materials to remain on-site and be used in the project, reducing the demand for new materials.
Building Reuse Parameters
Note that these measures only affect upfront emissions; refurbishments are counted normally.
Structure Reuse
The reuse of a pre-existing structural system for a given percentage of the building's floor area.
Opaque Enclosure Reuse
The reuse of opaque enclosure for a given percentage of the building’s total enclosure. Note that this measure only affects upfront emissions; refurbishments are counted normally.
Transparent Enclosure Reuse
The reuse of transparent enclosure for a given percentage of the building’s total enclosure. Note that this measure only affects upfront emissions; refurbishments are counted normally.
Roofing Reuse
The reuse of the roofing assembly for a given percentage of the building’s total roof area.
Interior Reuse
The reuse of interior fitout materials as a percentage of the total fitout.
Services Reuse
The reuse of MEP systems as a percentage of the total system.
Form and Massing
Building Perimeter
The user-declared perimeter of the building. In the absence of a user input, C.Scale assumes the building is an extruded square.
Floor-to-Floor Height
The vertical distance between building floors in feet. The default value is 13’.
Window-to-Wall Ratio (WWR)
The ratio of windows to total wall area. The default value is .45.
Energy Use
All Electric Building
The elimination of all onsite combustion and provision of 100% of the project’s energy use from electric sources.
EUI Target
Clean Power Purchase
The purchase of clean power through Direct Ownership, Green Retail Tariffs, Power Purchase Agreements (PPAs), Community Renewables or Utility Renewable Contracts (the five categories of renewables for which credit can be claimed in AIA 2030 commitment reporting) equivalent to the selected percentage of total energy use. The purchase of unbundled RECs should not be counted as a clean power purchase in C.Scale.
Clean Power Purchase Thresholds
0%. No purchase of clean power or RECs.
50%. Purchase of clean power to cover 50% of building energy use. This option assumes that these RECs are not time-matched, and discounts their effectiveness by 20% as they don't follow patterns of emissions on the electrical grid.
100%. Purchase of clean power to cover 100% of building energy use. This option assumes that these RECs are not time-matched, and discounts their effectiveness by 20% as they don't follow patterns of emissions on the electrical grid.
Solar Photovoltaic (PV) Array System Design
The addition of a solar PV array on the project site. The size of this array can be input in three forms:
Percentage of Load. The solar PV area size is calculated to account for the input percentage of building energy load.
Nameplate Capacity. The solar PV area size is input by its nameplate capacity in kW.
Area. The solar PV area size is input by its total area in square feet.
Solar PV orientation
The ability of solar PV arrays to produce electricity is related to their geometry and siting. Not all projects sites, such as partially shaded sites, will have an optimal solar orientation. This toggle has two options:
Optimal. There is no impediment on the site to maximum solar exposure.
Suboptimal. There is solar potential on the site, but it is partly compromised. A 20% penalty on solar energy production will be assessed.
Structure
Primary Structural System
Specification of a structural system other than the system modeled in the baseline. Note that this is not strictly a carbon reduction measure, as the substitution of some structural systems with some others can lead to an increase in embodied emissions.
Structural System Choices
Reinforced Concrete. A structural system comprised of columns, beams, and slabs of concrete reinforced with steel that provides tensile strength.
Mass Timber. A structural system comprised of massive beams, panels, and columns, often assembled by aggregating many smaller timber elements. This approach assumes that timber elements are aggressively substituted for other structural materials.
Wood Frame. A structural system comprised of dimensional lumber, plywood sheathing, and reinforced concrete cores and podiums.
Steel Frame. A structural system comprised of steel columns, beams, and girders connected with rigid or pin joints. Floors are steel decking with a concrete topping slab.
Hybrid Concrete-Steel. A structural system that combines rigid steel frames with concrete columns, beams, and slabs. These hybrid structures are more materially intensive and may be used when there are significant seismic loads, in high-rise buildings, or for programs with very high live or environmental loads.
Secondary Structural System
Specification of a secondary structural system, and its associated percentage of the overall building structure.
Concrete Specification
Concrete Specification Choices (Carbon Intensity)
Low Carbon (20th percentile). GWP in the 20th percentile of locally available concrete. Concrete with >50% replacement of cement by SCM, lower carbon aggregate, and careful sizing of concrete structural elements to reduce overspecification.
Average (50th percentile). GWP in the 50th percentile of locally available concrete. Concrete with 30-50% replacement of cement by supplementary cementitious materials (SCM) and careful sizing of concrete structural elements to reduce overspecification.
High Carbon (80th percentile). GWP in the 80th percentile of locally available concrete. Typical concrete mix, no effort made to lower carbon emissions.
Steel Specification
Steel Specification Choices (Carbon Intensity)
Low Carbon (20th percentile). GWP in the 20th percentile of locally available concrete. Concrete with >50% replacement of cement by SCM, lower carbon aggregate, and careful sizing of concrete structural elements to reduce overspecification.
Average (50th percentile). GWP in the 50th percentile of locally available concrete. Concrete with 30-50% replacement of cement by supplementary cementitious materials (SCM) and careful sizing of concrete structural elements to reduce overspecification.
High Carbon (80th percentile). GWP in the 80th percentile of locally available concrete. Typical concrete mix, no effort made to lower carbon emissions.
Timber Specification
The specification of lumber, plywood/OSB, and engineered timber elements with lower embodied carbon emissions. Choices are described in narrative form below. Narrative descriptions are approximate; there are many options that can yield similar carbon intensities.
Timber Specification Choices (Carbon Intensity)
Low Carbon (20th percentile) GWP in the 20th percentile of locally available timber . Wood products with the lowest GWP may come from value chains where wood waste is reused to make durable goods, electricity or biomass is used for process heat where possible, chemical inputs such as fertilizer are mostly avoided, climate-smart forestry practices increase forest carbon stocks over time and promotes the growth of complex older forest conditions, and the forest is near the mill and construction sites.
Average (50th percentile). GWP in the 50th percentile of nationally available timber. Lowering the GWP of wood products can be achieved by using wood waste instead of natural gas for process heat at the mill, limiting chemical inputs such as fertilizer, practicing forestry that increases or at minimum maintains forest carbon stocks over time and provides protection for older forests, and transportation by efficient means such as rail.
High Carbon (80th percentile). GWP in the 80th percentile of nationally available timber. The highest GWP forest products may come from value chains where fossil gas is used for process heat at the mill, forestry and nursery practices require high levels of chemical inputs, forestry practices utilize intensive short-rotation harvest regimes, and transportation is over long distances by truck.
Responsibly-Sourced Timber
In C.Scale, we identify three criteria contributing to the claim that wood products are responsibly sourced. While C.Scale does not prevent the user from counting the carbon storage benefits on other terms (as the list is nonexhaustive), we recommend meeting at least two out of the three criteria below in order to claim climate benefits from carbon storage.
Criteria for "Responsibly-Sourced Timber"
Transparent & traceable supply chain (required). Claims can be made about the environmental attributes of timber are impossible to verify without transparency and traceability in the supply chain. This means that a project team should be able to identify:
The source forest(s) or supply area(s)
This is the area from which a primary manufacturer sources most or all of its logs, typically a circle drawn around the location of the site of the mill, with the size being dictated by the maximum hauling distance of the logs.
The primary manufacturer mill(s)
E.g., sawmill, veneer mill, chip mill, etc.
The fabrication shop (for engineered timber).
Source forest has a growing carbon stock (optional). Carbon storage in wood products can only be claimed if the carbon stock of the source forest is maintained or increasing. This means that the forest area is managed and regenerates in a way that either preserves or increases the average level of carbon stored in vegetation and soils, or that high conservation value or high carbon stock forests are not replaced by less ecological valuable and carbon rich production forests.
Timber is certified, recycled, or reclaimed (optional). The use of recycled or reclaimed wood prolongs its storage of carbon and can displace the use of virgin timber. Certification by the Forest Stewardship Council (FSC) ensures that sound forestry, audit, and reporting practices are used.
Enclosure
Opaque Enclosure Specification
The specification of the opaque envelope assemblies. These specification levels do not describe specific assemblies. Instead, they approximate the 80th, 50th, and 20th percentile of the distribution of all opaque enclosure options.
Low Carbon (20th percentile). 20th percentile of GWP for opaque envelope assemblies. Maximize biogenic materials, innovate efficient assemblies, and reduce material use.
Average (50th percentile). 50th percentile of GWP for opaque envelope assemblies. Reduce redundancies and select low-carbon materials with high levels of recycled content.
High Carbon (80th percentile). 80th percentile of GWP for opaque envelope assemblies. Standard materials and assemblies, no effort made to lower carbon emissions.
Custom. Enter a custom carbon intensity.
Opaque Enclosure Refresh Rate
The length of time over which a majority of the opaque enclosure will be replaced.
Transparent Enclosure Specification
The specification of the transparent enclosure assemblies. These specification levels do not describe specific assemblies. Instead, they approximate the 80th, 50th, and 20th percentile of the distribution of all transparent enclosure options.
Low Carbon (20th percentile). 20th percentile of GWP for transparent envelope assemblies. Maximize biogenic materials, innovate efficient assemblies, and reduce material use.
Average (50th percentile). 50th percentile of GWP for transparent envelope assemblies. Reduce redundancies and select low-carbon materials with high levels of recycled content.
High Carbon (80th percentile). 80th percentile of GWP for transparent envelope assemblies. Standard materials and assemblies, no effort made to lower carbon emissions.
Custom. Enter a custom carbon intensity.
Transparent Enclosure Refresh Rate
The length of time over which a majority of the transparent enclosure will be replaced.
Roofing Specification
The specification of the roofing assemblies. These specification levels do not describe specific assemblies. Instead, they approximate the 80th, 50th, and 20th percentile of the distribution of all roofing options.
Roofing Specification Choices (Carbon Intensity)
Low Carbon (20th percentile). 20th percentile of GWP for roofing assemblies. Maximize biogenic materials, innovate efficient assemblies, and reduce material use.
Average (50th percentile). 50th percentile of GWP for roofing assemblies. Reduce redundancies and select low-carbon materials with high levels of recycled content.
High Carbon (80th percentile). 80th percentile of GWP for roofing assemblies. Standard materials and assemblies, no effort made to lower carbon emissions.
Custom. Enter a custom carbon intensity.
Roofing Refresh Rate
The length of time over which a majority of the roofing will be replaced.
Interior
Floor Area w/ Fit-Out
The percentage of floor space that will be fitted out for occupation by building tenants. The default value is 70%. If tenant fit-out is outside the project scope, this field can be set to 0%.
Interior Fit Out Specification
The specification of the fittings, furniture, and fixtures required for the use of the building by its tenants. These specification levels do not describe specific fit-outs or materials. Instead, they approximate the 80th, 50th, and 20th percentile of the distribution of all available data on tenant fit-outs.
Interior Fit Out Specification Choices (Carbon Intensity)
Low Carbon (20th percentile). 20th percentile of GWP for interior fitouts. Comprehensive low-carbon design and specification of tenant fit-out.
Average (50th percentile). 50th percentile of GWP for interior fitouts. Address "hot spots" (flooring, acoustic panels, casework, etc.).
High Carbon (80th percentile). 80th percentile of GWP for interior fitouts. Standard fittings, furniture, and fixtures, no effort made to lower carbon emissions.
Custom. Enter a custom carbon intensity.
Interior Fit-Out Refresh Rate
The length of time over which a majority of the interior fit out will be replaced.
Services
Conditioned Area
The percentage of total floor area that is heated or cooled.
MEP Specification
Embodied carbon in mechanical systems in evaluated at two specification levels—standard performance and high performance—and is dependent of the total square footage of the building. This approach, and the data used in C.Scale, follow from the CLF study on building mechanical systems.
Baseline buildings in C.Scale are always assumed to have a standard performance system. Scenarios that achieve an EUI reduction of more than 50% below the baseline are assumed to have a high performance system.
Embodied carbon in MEP is a data-scarce category, and we cannot confidently describe the potential to reduce embodied carbon in MEP systems through specification.
MEP Specification Choices (Carbon Intensity)
Low Carbon (20th percentile). 20th percentile of GWP for MEP systems.
Average (50th percentile). 50th percentile of GWP for MEP systems.
High Carbon (80th percentile). 80th percentile of GWP for MEP systems.
Custom. Enter a custom carbon intensity.
MEP Refresh Rate
The length of time over which a majority of the MEP systems will be replaced.
PV Specification
PV Specification Choices (Carbon Intensity)
Low Carbon (20th percentile). 20th percentile of GWP for PV systems.
Average (50th percentile). 50th percentile of GWP for PV systems.
High Carbon (80th percentile). 80th percentile of GWP for PV systems.
Custom. Enter a custom carbon intensity.
PV Refresh Rate
The length of time over which a majority of the PV systems will be replaced.
Solar ground coverage ratio
For any solar array entered as a decarbonization measure, this ratio describes the ratio of active solar cells to total array area. C.Scale's assumption is 0.7, representing an efficient solar layout.
Refrigerants
Total Refrigerant Charge
The reduction of the total quantity of refrigerants used in the buildings HVAC+R system.
Refrigerant Charge Choices (Carbon Intensity)
Low Carbon (20th percentile). 20th percentile of the total quantity of refrigerants used in the buildings HVAC+R system.
Average (50th percentile). 50th percentile of the total quantity of refrigerants used in the buildings HVAC+R system.
High Carbon (80th percentile). 80th percentile of the total quantity of refrigerants used in the buildings HVAC+R system.
Custom. Enter a custom carbon intensity.
Refrigerant GWP
The average global warming potential (GWP) of refrigerants used in the buildings HVAC+R system.
Refrigerant GWP Choices (Carbon Intensity)
Low Carbon (20th percentile). 20th percentile of GWP for refrigerants.
Average (50th percentile). 50th percentile of GWP for refrigerants.
High Carbon (80th percentile). 80th percentile of GWP for refrigerants.
Custom. Enter a custom carbon intensity.
Sitework
Planted Area
Set the percentage of site area, minus the building footprint, which is planted. This planted area is assumed to be a low carbon storage landscape, such as no-mow turfgrass or other herbaceous perennials. All unplanted area is assumed to be hardscape.
High Carbon Storage Planted Area
Set the percentage of the planted site area comprised of a high carbon storage landscape, such as dense broadleaf shrubs and trees in a matrix of no-mow turfgrass or herbaceous perennials.
Hardscape specification
The specification of the pervious and impervious surfaces on the building site (outside the building envelope. These specification levels do not describe specific materials or assemblies. Instead, they approximate the 80th, 50th, and 20th percentile of the distribution of all hardscape assemblies based on a set of standard details.
Low Carbon (20th percentile). 20th percentile of GWP for hardscape assemblies.
Average (50th percentile). 50th percentile of GWP for hardscape assemblies.
High Carbon (80th percentile). 80th percentile of GWP for hardscape assemblies.
Custom. Enter a custom carbon intensity.
Hardscape Refresh Rate
The length of time over which a majority of the site's hardscape will be replaced.
Jobsite
A5.2 Jobsite Emissions
Enter a custom carbon intensity (kgCO₂e/sf) for jobsite emissions related to construction activities and land use. The default value assumes 40 kgCO₂e/m² for construction emissions, which includes fuel, tools, and energy used on-site. This default is adjustable based on project-specific data. For greenfield sites, emissions from soil and vegetation are also calculated, using regional data to estimate carbon release from land development.
Demolished Area
Pre-construction demolition emissions are calculated per floor area of the demolished building, using a default factor of 35 kgCO2e/m2. This is a data-scarce category. Where project-specific data is available, this default can be overridden by the user.
The reduction of the building’s EUI by any of a number of strategies. If the you have not entered a custom EUI, the EUI is estimated via .
The specification of concrete with lower embodied carbon emissions. Choices are described in narrative form below, and the underlying data is listed in . Narrative descriptions are approximate; there are many options that can yield similar carbon intensities.
The specification of structural steel, steel deck, and reinforcing bar with lower embodied carbon emissions. Choices are described in narrative form below, and the underlying data is described in . Narrative descriptions are approximate; there are many options that can yield similar carbon intensities.
In accordance with ISO 21930, the carbon content of biogenic materials can only be counted as carbon-storing if the timber comes from a forest managed with sustainable practices. An example of this is timber from an FSC-certified forest. For more information, please refer to C.Scale methodology for or the procurement guidance from the .
Embodied carbon in solar photovoltaics arrays is calculated using values from the peer-reviewed literature. A citation to the current data source is available in in the section of this guide.
