Butterfly design: Helene Partan, age 8, a second-grade student at the Tobin Montessori School, Cambridge.
Exhibition material: White thermoplastic Polyoletin (TPO) roofing membrane, acrylic paint
Proposed materials for project implementation: White ENERGY STAR® paint, a cool roof material, or TPO roofing membrane applied to black roofs; butterfly artwork applied on roof with acrylic paints. The artwork can also be applied to existing white roofs.
Partner: City of Cambridge
We wish to thank Eastern Architectural Representatives and Firestone for their generous donation of UltraPly TPO membrane for this exhibition.
Simulation of cool roofs in Cambridge. Photo by Christopher Schmidt.
If the flap of a butterfly’s wings can be instrumental in generating a tornado, it can equally well be instrumental in preventing a tornado.
—Edward N. Lorenz, 1972
Cool Roofs is a remarkably simple concept: cover flat roofs in our city with a white roofing material or white ENERGY STAR® paint and use the roofs as canvases for enormous butterfly murals created by the K-12 students from the Cambridge community. The project was inspired by “the butterfly effect,” a phrase coined by MIT meteorology professor Edward N. Lorenz to describe his discovery that tiny changes in initial conditions can lead to dramatically different outcome on a larger scale. Lorenz was talking about weather, but the butterfly effect applies to this public initiative as well. The small act of changing the color of our roofs from black to white decreases the urban heat island effect by lowering temperatures through the reflection of sunlight. The creation of the butterfly mural artwork fosters civic pride and engagement.
Environmental and Economic Benefits
The City of Cambridge is aware of the growing impact of climate change and is studying issues like urban heat islands. Densely populated metropolises like Cambridge tend to be “heat islands”—they are significantly hotter than the surrounding area. White TPO (thermoplastic polyolefin) roofing membranes and white ENERGY STAR® paint increase the roof’s albedo (the energy from the sunlight that casts back into the atmosphere), reflecting heat away from the building, which is why white roofs are also called Cool Roofs. Specific benefits include:
Improved indoor comfort. Cool roofs lower the indoor air temperature during the hotter months, promoting productivity and occupant health. The need for cool roofs is particularly acute in the city because many neighborhoods lacks the cooling canopy of abundant shade trees.
Energy and cost savings. Occupants in buildings with cool roofs are less dependent on air conditioning, saving energy and money. The conservation of energy in turn reduces the emission of pollutants like carbon dioxide from electric power plants.
Cooler outside air. Cool roofs reduce the amount of heat transferred from buildings to the air.
Better air quality. Decreased air temperatures slows the formation of ground-level ozone. Ozone, the primary component of smog, can aggravate respiratory illness and can act as a greenhouse gas.
Slowed climate change. Cool roofs decrease the heat absorbed at the Earth’s surface, offsetting warming caused by greenhouse gases.
Reduced electrical grid strain. The diminished demand for cooling energy will also moderate peak energy demand on hot days, decreasing the risk of power outages.
Individual and Community Benefits
Perhaps less tangible than the benefits outlined above, these emotional benefits are no less significant.
Pride in ownership. Participating building owners can acquire one LEED point for “reduced heat island effect.”
Inspiration and Education. The project is a positive, proactive means of involving an entire community in learning about and combating climate change.
Community pride. This project creates a unique opportunity for everyone in the city (residents and business owners alike) to take ownership in improving their neighborhood, their health, and their community.
Creativity. Students from the city’s K–12 schools will generate the butterfly artwork used in the project.
Eligible roofs. Roofs covered in white TPO (thermoplastic polyolefin) roofing membrane. Owners should consider this material when it is time to replace their black roof.
Eligibility for painting roofs. Black roofs will be painted with a white ENERGY STAR® paint. Roofs must be flat, in good repair, have easy access, and be made of smooth asphalt, granule, or smooth aluminum.
Selecting the artists. There will be a call for art creation participation through Cambridge schools and community centers.
Creating the butterfly murals. Artwork created by the K–12 community will be applied by adult mural artists to the cool roofs. So that the cooling properties of the white paint will not be compromised, the artwork paint will not exceed 20% of the total square foot area of the roof.
Accessibility to the murals. There will be a website devoted to the Cool Roofs with documentation and drone photography. The murals can also be visible by way of Google maps in satellite mode where everyone can experience the artwork as an online exhibition.
By way of satellite and Google Maps the butterfly artwork can be viewed as an online exhibition.
Thank you to Eastern Architectural Representatives and Firestone for their donation of the white roof material for the exhibition.
Example of Combined Effects of Solar Reflectance and Thermal Emittance on Roof Surface Temperature
On a hot, sunny, summer day, a black roof that reflects 5 percent of the sun’s energy and emits more than 90 percent of the heat it absorbs can reach 180°F (82°C). A metal roof will reflect the majority of the sun’s energy while releasing about a fourth of the heat that it absorbs and can warm to 160°F (71°C). A cool roof will reflect and emit the majority of the sun’s energy and reach a peak temperature of 120°F (49°C).
About the artist
Jean Wilcox has deep roots in Cambridge, having lived and worked in the city for over 27 years. Through her Central Square-based graphic design studio, Wilcox Design (wilcoxinc.com), she has created publications, websites and brand identities for such arts and cultural organizations as the Smithsonian Institution, Solomon R. Guggenheim Museum, Metropolitan Museum of Art, Harvard University and the Fitchburg Art Museum.
Keith Oleson of the National Center for Atmospheric Research in Boulder, Colorado stated in the article “Effects of white roofs on urban temperature in a global climate model” that if every roof in large cities around the world were white it would decrease the urban heat island effect by 33%. I was struck by the simplicity of this solution.
As a graphic designer my task is to communicate ideas and concepts in a clear and concise way. Looking at the Butterfly Effect as a model for climate change, I envisioned the white roofs as blank canvases for artwork. The butterfly is a symbol of endurance, change, hope, life, and transformation because of its impressive process of metamorphosis. There is a long history of mural art painting in Cambridge, dating back to the early 1970s. This cool roofs project extends the community-building initiatives of the mural arts movement with a green twist, creating cool art for a hot climate.
Related City Resources
The City launched Cambridge Energy Alliance over 10 years ago to help Cambridge residents save energy, save money, and cut their carbon footprint. CEA seeks to make it easier for Cambridge residents and small businesses to access the significant incentives available through state and utility programs for energy efficiency and renewable energy. Indeed, by taking advantage of no-cost/low-cost measures and financing opportunities, energy-saving projects and solar solutions can help residents save significant money from day one. The actions that Cambridge residents take play an important role in achieving our climate goals: buildings in Cambridge are responsible for over 80% of our carbon emissions, and implementing significant energy efficiency and renewable energy in existing residential buildings will be a huge part of getting to our Net Zero goals.
project models and inspiration
The New York City Cool roofs project served as our inspiration https://www1.nyc.gov/nycbusiness/article/nyc-coolroofs
In 2018 The New York Times wrote 5 Ways to Keep Cities Cooler During Heat Waves, painting roofs white was on the list: https://www.nytimes.com/2018/07/24/climate/heat-waves-cities.html
Yale Environment 360
Urban Heat: Can White Roofs Help Cool World’s Warming Cities?
The Cambridge Community Development Department has evaluated the benefits of solar panels with a tool that includes a heat map of the roofs of Cambridge. The solar panel information indicates how much sun exposure each roof gets. This information can also be used when considering a white roof, showing building owners to what extent their roof is exposed to sunlight.
For more information, see: https://www.mapdwell.com/en/solar/cambridge
Modeled Net Energy Cost Savings ($/1,000 ft) in Various Cities for Widespread Use of Cool Roofing
Konopacki, S., L. Gartland, H. Akbari, and I. Rainer. 1998. Demonstration of Energy Savings of Cool Roofs. Paper LBNL-40673. Lawrence Berkeley National Laboratory, Berkeley, CA.