Philadelphia Water Department


July 8, 2016 - Green Roof Density Bonus

On December 23, 2015, The Philadelphia Zoning Code was amended to offer exceptions to some residential density rules when a development project includes a green roof that meets certain criteria. If these criteria are met, a density "bonus" will allow for the development of additional residential units in areas where such development would normally be restricted. Zoning districts eligible for the density bonus include RM-1, CMX-2, and CMX-2.5. To determine if your development qualifies for the Green Roof Density Bonus, please refer to the conditions outlined in Section 14-602.7 of the Philadelphia Zoning Code ("Exception to Use Tables for Green Roofs"). Development projects applying for the bonus must obtain PWD review, as specified in PWD's Green Roof Density Bonus Factsheet.

Why Should I Apply?

This change to the Zoning Code provides a benefit to the developer by offering an opportunity to construct additional units while also incentivizing the utilization of green roofs in development projects. Developers who construct green roofs as a part of their development may be eligible to apply for tax breaks to reduce the cost of green roof installation.

Green roofs deliver numerous triple bottom line benefits:

  • Stormwater management - Not only aiding the developer in meeting the City's Stormwater Regulations but also reducing pollutants reaching the City's waterways
  • Reduced heat island effect
  • Improved air quality
  • Increased green jobs
  • Reduced costs to the owner due to extended roof life and improved insulation for both heating and cooling

The amendment to the Zoning Code and PWD's application requirements for the Green Roof Density Bonus can be referenced below:

July 1, 2015 – Philadelphia Water's Stormwater Regulations Update

Effective July 1, 2015, Philadelphia Water updated its Stormwater Regulations for development to meet requirements of the Clean Water Act. The changes will improve the health of Philadelphia’s rivers, minimize local flooding, and encourage the use of green infrastructure throughout the city. The revised Stormwater Management Guidance Manual, Version 3.0 contains policies and procedures that reflect the new Stormwater Regulation requirements and offers enhanced resources to the development community with respect to stormwater management.

Which Stormwater Regulations apply to your project?

Projects that submit a complete Existing Resources and Site Analysis (ERSA) Application to PWD prior to July 1, 2015 will be eligible to meet the current Stormwater Regulations. Projects submitting ERSA Applications on July 1 or later will be required to meet the updated Stormwater Regulations.

What do the July 2015 Stormwater Regulations achieve?

  • Manage more water. Each development project will hold more water on site.
  • Slow water entering sewers. The rate of stormwater entering the sewer system will be slower.
  • Cleaner water entering sewers. Each site will filter the dirtiest stormwater running off the site.

What else is changing?

As we updated the Stormwater Regulations, Philadelphia Water also improved how we work with the development community.

Our customers can expect:

  • Faster project approvals. A new expedited, 5-day review for surface green stormwater infrastructure.
  • Clear application resources. Simplified ERSA Application and worksheets to improve submissions.
  • Accessible information. Online, user-friendly Guidance Manual and new Stormwater Plan Review website.

Summary of Regulatory and Technical Changes:

Acceptable Non-Infiltrating Pollutant-Reducing Practices
  Section Combined Sewer Area Separate Sewer Area or Direct Discharge
Bioretention 4.1 Yes Yes
Porous Pavement DIC 4.2 Yes Yes
Green Roofs 4.3 Yes Yes
Cisterns 4.5 Yes Yes
Blue Roofs 4.6 Yes No
Ponds and Wet Basins 4.7 Yes Yes
Vegetated Media Filters 4.9 Yes Yes
Media Filters 4.9 Yes Yes
Roof Runoff Isolation* 3.2.4 Yes No

*Roof runoff isolation is the routing of runoff from non-vehicular roof area that is not commingled with untreated runoff. The designer is referred to Section 3.2.4 for more information.

For more detailed information about the changes and our outreach to the development community, visit