Coated Construction Granules for High Near-Infrared Reflectivity
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Solution Overview
Problem
Conventional roofing materials with granules reflect little near-infrared radiation, leading to significant solar heat absorption and elevated temperatures, which contributes to heat-island effects, especially in dark-colored shingles, and existing solutions for improved reflectivity are either aesthetically unpleasing or costly.
Innovation Solution
Coated construction granules with a thin film that transmits visible light and reflects near-infrared radiation, applied using methods such as chemical vapor deposition, allowing for the creation of dark-colored roofing materials with enhanced NIR reflectance while maintaining aesthetic appeal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If white- or light-colored pigments or coatings are applied to roofing articles to enhance reflectivity, then solar reflectance is improved, but aesthetic appeal deteriorates
Solution Approach 1:
The solution segments the spectral response into different wavelength ranges: the thin film is designed to reflect near-infrared radiation (700-2500 nm) while transmitting visible light (300-700 nm). This spectral segmentation allows the roofing material to achieve high solar reflectance through NIR reflection without requiring light-colored pigments that would compromise aesthetic appeal.
Solution Approach 2:
A thin film coating acts as an intermediary layer between the granule surface and the incident radiation. This thin film mediates the interaction by selectively reflecting NIR radiation while allowing visible light to pass through, enabling dark-colored roofing materials to achieve high solar reflectance without sacrificing aesthetics.
2Loss of energy
If metal flakes such as aluminum flakes are adhered to roofing article surfaces to provide radiation reflectivity, then solar reflectance is improved, but aesthetic appeal deteriorates
Solution Approach 1:
The invention replaces expensive and aesthetically unpleasing metal flakes with a thin film coating that can be applied at low cost. The thin film provides the necessary NIR reflectivity without the metallic appearance, offering a more economical and aesthetically pleasing alternative that maintains consumer preference for dark-colored roofing articles.
3Ease of manufacture
If dark-colored cool pigments are used on roofing articles to provide desired color and NIR reflectance, then aesthetic appeal is improved, but cost increases and solar reflectance is limited
Solution Approach 1:
The invention changes the key parameter of the coating from bulk pigment concentration to thin film thickness. By using extremely thin films (5-5000 nm) that are transparent to visible light but reflective to NIR radiation, the system achieves high solar reflectance in dark-colored materials without relying on expensive cool pigments. The thin film parameters (thickness, composition) are optimized to provide the desired optical properties.
4Ease of manufacture
If NIR-transparent pigments are disposed atop a NIR-reflective substrate to achieve dark hues, then aesthetic appeal is improved, but cost increases and solar reflectance is limited
Solution Approach 1:
The invention merges the functions of the substrate and coating into a unified thin film structure. Rather than using a separate NIR-reflective substrate with transparent pigments on top, the thin film itself is designed to perform both functions: it provides NIR reflection while remaining transparent to visible light, achieving the desired aesthetic and functional properties in a single integrated layer.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The coated granules effectively reduce the heat-island effect by reflecting a substantial portion of near-infrared radiation, thereby lowering surface temperatures and addressing the aesthetic and cost limitations of existing solutions.
Implementation Method 1
the at least one thin film reflecting from about 1% to about 100% of radiation having a wavelength of between about 700 nm and about 2500 nm
Implementation Method 2
the at least one thin film transmitting from about 5% to about 100% of radiation having a wavelength of between about 300 nm and about 700 nm
Implementation Method 3
applied using methods such as chemical vapor deposition
Data Source
AI summary
Disclosed are construction granules surmounted by at least one thin film having substantial reflectance of near-infrared radiation, substantial transmittal of radiation in the visible light range, and substantial emissivity in the medium-infrared range to render the granules energy-efficient and aesthetically pleasing. Also disclosed are related methods for fabrication of the construction granules.