Title
Discussion on Residential Density Calculations
The purpose of this discussion item is to evaluate whether the Village’s current approach to residential density calculations - based on Net Buildable Acres - continues to effectively support community goals, and to consider targeted amendments that better align with contemporary development practices and fiscal sustainability.
History
In October 2025, a text amendment was presented to the Board of Trustees (Case #2025-0584) that proposed modifying how dwelling units per acre are calculated in residential zoning districts. The amendment recommended shifting from a net buildable acreage standard to a gross acreage approach. The Board did not approve this change, signaling a preference to retain a framework that accounts for site-specific constraints in determining allowable density.
Staff is proposing an alternate amendment for your consideration.
In the R-3, R-3A, R-4, and RSB zoning districts, residential density is currently calculated based on net buildable acreage. The proposed amendment refines the definition of net buildable acreage and updates the density bonus criteria to improve clarity, consistency, and alignment with the Village’s broader growth and development objectives. This approach provides numerous benefits to both the Village and the development community.
How is Density Calculated
In the R-3, R-3A, R-4 and RSB Zoning Districts, density of a development is calculated based on the Net Buildable Acreage.
Current Definition
Net Buildable Acres are calculated by deducting the following from the gross acreage of land:
• 50% of ComEd easement if owned by the petitioner and the space serves as a public open space amenity
• Floodplain that must be conserved
• Wetlands that must be conserved by federal, state, or local requirements
• Perimeter road right-of-way (ROW) dedication
• 50% of land required for a park or school dedication
• Detention and retention areas up to the high-water level
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