Residential Floor Area Allocation
The Residential section of the Floor Area Allocation panel is used to describe how residential building area and dwelling units are distributed among dwelling unit types, yielding dwelling unit densities. Household and population densities are subsequently determined according to project-level variables for residential building occupancy and household sizes by dwelling unit type; see Using Library Settings for details.
Residential section of the Floor Area Allocation panel
Gross floor area. The amount of gross floor area dedicated to residential uses. The value is set in the Building Characteristics panel and displayed here for reference.
Net floor area. Includes two values: a net floor area percentage and the resulting total net residential floor area in the building. Net, or leasable, floor area is calculated as the product of the net floor area percentage (also known as a net-to-gross ratio) and gross floor area. For single family building types, the net floor area percentage is typically 100%, while that for multifamily building types with internal hallways and common areas is lower.
Distribution by dwelling unit type. Inputs for each dwelling unit type include net floor area, number of units, and average unit size. The values are tethered such that net floor area is the product of the number of units and average unit size. Average unit size is expressed in terms of net floor area. The net floor area across all types must add up to the net floor area value for residential building area as specified above.
  • Single-family large lot. UrbanFootprint defines large lot homes as those with lot sizes of 5,500 square feet and above. The distinction between large and small lot single family homes supports the use of differentiated assumptions for household size, as well as analysis assumptions for energy and water use.
  • Single-family small lot. UrbanFootprint defines small lot homes as those with lot sizes under 5,500 square feet. The distinction between large and small lot single family homes supports the use of differentiated assumptions for household size, as well as analysis assumptions for energy and water use.
  • Single-family attached. Includes townhomes, rowhomes, duplexes, and other single-family home types with shared walls.
  • Multifamily. Refers to housing in which multiple units are contained within a single building or group of buildings.
  • Accessory. Refers to a secondary dwelling unit on a lot occupied by a primary dwelling unit, typically a single-family home.
  • Overallocated / Unallocated. A value that appears if the total of the net floor area values by dwelling unit type falls above or below the total net residential floor area as specified. Use this value to correct the floor area allocations. The Component will not be valid for use if there is any overallocated or underallocated area.

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