Cool Roof Coatings Incorporating Glass Hollow Microspheres

EPA Grant Number: SU833924
Title: Cool Roof Coatings Incorporating Glass Hollow Microspheres
Investigators: Barsoum, Michel , Woods, Charlie , Reid, Courtney , Pugh, Daniel , Eisele, Eric , Byrnes, Sarah
Current Investigators: Barsoum, Michel , Woods, Charlie , Reid, Courtney , Pugh, Daniel , Eisele, Eric , Hagarman, James , Byrnes, Sarah
Institution: Drexel University
EPA Project Officer: Page, Angela
Phase: I
Project Period: August 15, 2008 through August 14, 2009
Project Amount: $9,999
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2008) RFA Text |  Recipients Lists
Research Category: P3 Challenge Area - Air Quality , P3 Challenge Area - Chemical Safety , Pollution Prevention/Sustainable Development , P3 Awards , Sustainable and Healthy Communities


Solar Gain is in part responsible for up to 56% of energy consumed by cooling systems in residential buildings. By reflecting and scattering radiant energy from the sun, the surface temperature of exterior walls and roofs can be greatly reduced. Previous studies have indicated that although TiO2 based white paints are highly efficient at scattering visible light, absorption occurs for wavelengths of 650nm and higher. A coating utilizing a filler with a broad particle size distribution will reflect solar radiation from a broad range of wavelengths. Preliminary data suggests that glass hollow microspheres are the ideal candidate for scattering light from the visible region well into the near infrared region. Glass hollow microspheres are easily integrated into traditional binder systems such as acrylic or latex base, are fire retardant, and manufactured from commodity raw materials. By optimizing the particle size distribution and packing factor of the glass hollow microspheres, highly efficient, low solar gain coatings are possible. Optimization of the coating will involve a thorough analysis and characterization of starting material blends, characterization of mixed coatings and microstructural characterization of dried coatings.


In order to design an architectural coating capable of scattering and reflecting UV, Visible, and NIR radiation from the sun, the filler (scattering) particles must be optimized for full spectrum scattering. Our team will use glass hollow microspheres due to their preferred optical properties and low cost to create an architectural coating capable of significantly reducing solar gain on the exterior of a building.


By using Mie Theory as a basis for optimal particle size necessary to scatter a particular wavelength, a filler medium with preferred optical properties will be designed to encompass a corresponding particle size distribution, based on wavelengths to be scattered. The filler medium, or microspheres, will be bound by conventional binder systems such as latex or acrylic. Optical testing will be done on the microspheres to ensure proper scattering, and microstructural characterization will be conducted on coatings to optimize sphere distribution. Further work done on this project, budget permitting, includes field testing an optimized coating on an experimental property at Drexel University outfitted with proper measurement facilities.

Expected Results:

Our team expects to create a low cost architectural coating which significantly reduces solar gain, compared to traditional titanium dioxide based paints and coatings.

Supplemental Keywords:

Syntactic coating, close packed hollow microspheres, Qcel, NIR reflective glazing, solar gain, roof coating,

Relevant Websites:

Phase 2 Abstract

Progress and Final Reports:

  • Final Report
  • P3 Phase II:

    Cool Roof Coatings Incorporating Glass Hollow Microspheres for Improved Solar Reflectance