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Lighten all municipal parking lot surface temps with white paint & healthy tree boats



In Cambridge there are at least 11 municipal surface parking lots and more than 55 private parking surface lots.  All of them are black asphalt and most have no trees within the parking lot itself.  It is well known that black asphalt absorbs heat and contributes greatly to the Urban Heat Island Affect. Painting the entire surface of a parking lot white or with a high solar reflectivity coating as well as appropriate tree planting will dramatically increase a local albedo effect and reduce the local heat island effect.

The obvious and unexpected use of white or high solar reflectivity paint on parking lot surface would engender a teaching moment for the curious pedestrian or driver. 

Category of the action


Who will take these actions?

Initially Cambridge would paint all its surface lots white (or use high solar reflectivity coating) and have a control group of untreated private surface parking lots.  Local academic talent (students) would  measure continuous surface temperatures over summer months  in all treated municipal parking lots & control black lots to determine what the reduction is. Significant reduction in surface temperatures may convince private property owners and other municipalities to lighten their surfaces as well. Eventually there may be a municipal requirement for property owners to reduce heat effects from their property. 

What are other key benefits?

The unexpected use of white paint or a different coating will cause questions and there could be signage in the lots to explain benefits & educate about Heat Island effect. 

Surface runoff from black asphalt has higher temperature.  Warmer water entering receiving waterbody from this runoff leads to lower oxygen content further degrading urban waters such as the Charles and Mystic Rivers.  Light surfaces should lead to cooler water entering urban rivers.

An added benefit is reducing vapor loss of gasoline from tanks of cars if they are parked in shade of tree. 

Trees are always a benefit for much more than the shade, wildlife habitat and storm water management features they provide! Esthetics and calming are important too. 

As each local property owner adopted the white paint in their parking lots, they could become part of the White Knights, a premier designation for environmentally conscious entities. 

What are the proposal’s costs?

The cost of main project is cost of durable white/high reflectivity paint and the labor to apply and maintain it. Also labor involved in periodic, strategic washing of surfaces. As more parking lots converted to reflective surface, bulk rate of specialized paint could be shared between private property owners and the municipality. 

The design, installation and maintenance of tree "boats" on the parking lot would be another cost. 

Initial study analysis would be cost of student interns for Summer and Fall project. This would include cost of equipment for continuous temperature reading in experimental (white lot) and control (black lot).

If the surface of the newly painted lots became more slippery, textured could be added to the paint or during the application process.

The durability of high traffic parts of the parking lot may need more maintenance or washing than other parts. "Carbon Black" is used to improve performance of auto tires and it is likely to be visible as it rubs onto light surfaces.

Time line

The pilot program to compare actual temperature reductions (experimental v. control) could take less than one year. During the pilot year, a maintenance schedule for repainting high traffic areas would be established. 

A power-washing or repainting schedule would be part of an ongoing and long-term maintenance program.

If this White Knight idea catches on, it would be easily transferable to private parking lots and other municipalities in the short-term.  

Related proposals


most of the published literature is about solar reflectivity of roofs not pavements or parking lots.