Chicago's Cool Roof Rule: What It Means When You Replace a Flat Roof
Inside the City of Chicago, a replacement flat roof has to meet a reflectance standard. It catches homeowners, condo boards and small building owners off guard at permit time.
The short version
Chicago's building code requires low-slope roofs to have a reflective surface. When you replace a flat or low-slope roof inside the city, on a garage, a rear porch, a bungalow addition, a two-flat or a commercial building, the new roof generally has to meet that standard. A standard dark granulated modified bitumen cap sheet does not. The rule lives in the Chicago Building Code at section 14B-15-1515, and it applies to the roofing you choose, so it belongs on the estimate, not as a surprise at inspection.
What the standard asks for
The requirement is about solar reflectance. As we read the current code, a low-slope roof needs an initial solar reflectance of at least 0.72, or a three-year aged reflectance of at least 0.50, with the product's rating published by the Cool Roof Rating Council. Vegetated roofs and roofs with heavy ballast are the main exceptions. Your contractor should be able to name the product, its rating and where that rating is published.
What usually qualifies
White TPO membranes typically meet the standard. Modified bitumen can, but only with a reflective cap sheet or a qualifying reflective coating rather than the standard dark granulated cap. On a small porch or garage roof the difference in material is modest; the important thing is that the product chosen is one that meets the rule. Our TPO vs modified bitumen comparison covers how the two systems differ beyond color.
Insulation can come into it too
Replacing a low-slope roof can also bring the energy code's insulation requirements into play, particularly on residential buildings where insulation sits above the deck. On some buildings that raises the roof surface enough to affect parapet and flashing heights, which in turn can change the scope of the masonry work. This is the conversation to have before material is ordered, and it is why we ask about the building's height, use and existing insulation at the estimate.
Permits and who can do the work
A roof replacement in Chicago needs a City permit, and the contractor needs a City of Chicago General Contractor license. We hold one (Class E, #TGC147129), file the permit, and specify a compliant product on the estimate so the permit and the inspection go through cleanly. Parapet and chimney masonry is done by a City-licensed mason working under the project.
Condo boards and small buildings
Condominium associations and owners of two-flats and small mixed-use buildings run into this rule most often, because their roofs are mostly flat. We work with boards on the specification, the permit and the schedule; a recent example is the 12-unit low-slope recover in Irving Park on our Our Work page.