Envelope

Envelope Quantity Takeoffs

The building envelope in divided into three components: opaque cladding, glazing, and roofing. The area of each is calculated based on user inputs for building floor area, number of floors, floor-to-floor height window-to-wall ratio (WWR), and building perimeter. C.Scale makes a preliminary estimate of floor-to-floor height, WWR, and building perimeter (assuming a square building) which the user can refine in the "overrides" panel in the base case tab.

$$Envelope \ area = Perimeter \ * \ F2F \ Height \ * \ Number \ of \ floors$$

$$Glazing \ area = WWR \ * \ Perimeter \ * \ F2F \ Height \ * \ Number \ of \ floors$$

$$Cladding \ area = (1-WWR) \ * \ Perimeter \ * \ F2F \ Height \ * \ Number \ of \ floors$$

$$Roof \ area = Building \ Footprint$$

Floor-to-Floor Height

Floor to floor (F2F) height can be set in the API for each floor individually (if using the stacked BuildingForm object) or for all floors together (in the simple BuildingForm object). Default values for floor-to-floor height are set by use type, as described in the table below.

Use Categories	Default F2F Height (ft)	Default F2F Height (m)
Dormitory, Hotel, Multifamily Housing, Senior Care Facility, Single Family Home	11.5 feet	3.5 meters
Fitness Center, K-12 School, Medical Clinic, Office, Pre-school / Day Care, Restaurant, Retail Store, University/College	13 feet	4.0 meters
Aquarium, Hospital, Laboratory, Library, Museum, Performing Arts, Post Office, Stadium, Transit Station, Worship Facility, Zoo	15 feet	4.6 meters
Convention Center	18 feet	5.5 meters
Distribution Center, Warehouse	20 feet	6.1 meters

Parametric Envelope Model

C.Scale includes a dynamic envelope model which allows users to input very general data (when very little is known) or very specific data (during later stages of design).

When specific data is not known, the API includes C.Scale's pre-defined carbon intensities, defined by the levels of ambition:

• Conservative represents the 80th percentile of material or assembly carbon intensities.

• Best Practices represents the 50th percentile of material or assembly carbon intensities.

• Low Carbon represents the 20th percentile of material or assembly carbon intensities.

When more data is available, C.Scale allows you to define specific cladding assemblies, exterior insulation types, and wall framing assemblies. Using the description parameter in the envelope.cladding or envelope.glazing section of the request, you can pass in a more precise definition of the opaque building envelope. Where one or more layers of the assembly is unknown (or up for discussion, pass a None parameter.

C.Scale will use your description of the envelope (i.e., any declarations of specific materials) to subset our library of envelope assemblies (~1200) to only those meeting your criteria. The API will use the relevant specification parameter to choose the 20th, 50th, or 80th percentile of that subset. This allows the user to know the range of potential carbon intensities available both within and between their declared design.

• If all parameters are None (no design criteria entered), then we evaluate the percentile from the full set of envelopes in our database (~1200 modeled envelope assemblies).

• With the user selects their design criteria, we subset the data used to generate these percentiles. For instance, if a user selects a Timber Rainscreen cladding, we will return the 20th, 50th, of 80th percentile of all envelope assemblies in our database with a Timber Rainscreen (~100 modeled envelope assemblies).

Multiple envelopes can be described for a building by passing a list of descriptions. The relative proportion of each envelope is described with the proportion field with each description. The API will normalize all proportion entries to the total opaque envelope area. This means that a use can pass in proportions of 20000, 25000, and 5000 (representing m2 of envelope area) or of 0.4, 0.5, and 0.1 (representing the same assemblies as proportions of the total).

In all cases, user-declared carbon intensity data can be entered on a kgCO2e/m2 (of kgCO2e/sf) basis for each component of the envelope.

Opaque Envelope

Cladding Assemblies

Cladding assemblies available via API:

• Granite Veneer

• Limestone Veneer

• Brick Veneer

• EIFS

• Glass Fiber Reinforced Concrete Rainscreen

• Aluminum Composite Panel Rainscreen

• Terracotta Rainscreen

• Fiber Cement Rainscreen

• Formed Zinc Panel Rainscreen

• Thin Brick Rainscreen

• Formed Steel Panel Rainscreen

• Hardwood Rainscreen

Exterior Insulation

Exterior insulation types types available via API:

• Mineral Wool

• PolyIso

• XPS

• EPS

Wall Framing

Wall framing types available via API:

• 6in (152mm) CMU

• 3.625in (92mm) Metal Stud | 16in (400mm) Spacing

• 3.625in (92mm) Metal Stud | 24in (600mm) Spacing

• 2x4 (50x100mm) Wood Stud | 24in (600mm) Spacing

• 2x4 (50x100mm) Wood Stud | 16in (400mm) Spacing

• 6in (152mm) Metal Stud | 16in (400mm) Spacing

• 6in (152mm) Metal Stud | 24in (600mm) Spacing

• 2x6 (50x150mm) Wood Stud | 24in (600mm) Spacing

• 2x6 (50x150mm) Wood Stud | 16in (400mm) Spacing

Data in the C.Scale envelope model makes use of Payette Kaleidoscope data for some assemblies by permission. Find the full citation for these data in the Reference Data section of the methodology.

Default R-Values

The declared R-value of the assembly is used to calculate the amount of exterior insulation needed. R-values for framing assemblies are de-rated using the nominal R-values in ASHRAE 90.1-2019 Appendix A. If an R-value is not declared by the user, the default is set by climate zone.

ASHRAE Climate Zone	C.Scale Default R-Value
Climate Zone 0	18
Climate Zone 1	18
Climate Zone 2	18
Climate Zone 3	20
Climate Zone 4	21
Climate Zone 5	2
Climate Zone 6	26
Climate Zone 7	26
Climate Zone 8	29

Transparent Envelope

Mullion/Frame Material

Mullion/frame types available via API:

• Steel

• Timber/Aluminum

• Aluminum

• Timber

Insulated Glazing Unit (IGU)

IGU types available via API:

• Double-glazed IGU

• Triple-glazed IGU

Roofing

Parametric roofing model coming soon!