This dissertation conceptualizes and computationally demonstrates a photometric characterization methodology for daylighting fixtures. The methodology is based upon applying far-field photometric evaluation techniques. The photometric characterization methodologies use computer simulations to characterize visible light and thermal performance of daylighting fixtures. A daylighting fixture is defined to include the boundary and all the components that exist between the admittance plane and exit plane of a daylighting aperture. The fixture concept allows the characterization data to be applied to daylighting fixtures in any setting. The lack of comprehensive daylighting performance evaluation protocols and basic daylighting component research indicate the need to develop this characterization methodology. This dissertation articulates key weaknesses in current daylighting indicators and performance characterization research, which support the need for additional protocols to characterize daylight, including angular intensity distribution at the point it is admitted into a building and associated thermal gains. The characterization methodology is demonstrated using four lighting software programs to assess louver control components for toplighting. Visible light characterizations addressed in this dissertation study include angular intensity distribution, illuminance distribution and visual effect. Thermal characterizations addressed include irradiance transmittance through the aperture and heat gain associated with irradiance absorbed by the louver control component. Simulations are limited to using currently available computer tools. Where simulation tools do not exist to properly support the characterization, a description is given of the software capabilities that need to be developed. The characterization data provided by this methodology is fully compatible with electric lighting and glazing performance data currently used by designers. The proposed methodology will support architects and lighting designers in selecting daylighting components and/or systems on a performance basis comparable to the selection of other building products. Given the huge potential for daylighting, the lack of well daylighted buildings indicates the potential for this research. Daylighting in buildings has implications for renewable energy, and the health and well-being of human occupants. It is envisioned that the proposed photometric characterization data will be used by architects and lighting designers to develop daylighting strategies incorporating performance, experiential, and aesthetic criteria.