Masters Thesis

My masters thesis was about developing new methods to study complex window systems for use in high performance buildings. Specifically, I developed new methods to calibrate a CCD and InGaAs near infrared camera to measure the radiance of unknown polychromatic spectra reflected or transmitted from a fenestration system in a custom made video-goniospectroradiometric device. From these measurements, the quasi-spectral bi-directional transmissiona and reflection distribution functions of complex fenestration systems can be quantified for use in building lighting and energy simulation tools and the characterization of new window systems. The new approach also enabled the development of spectral estimation methods studied by Kellie Stokes under the guidance of Marilyne Andersen to refine the spectral bi-directional functions estimated for each system.

This research extends efforts by the building science community to quickly measure the bi-directional transmission or reflection distribution functions (BT(R)DF) of window systems. Devices called goniophotometers are well-established tools used for analyzing the interaction of light with window systems. Our goniophotometer uses an innovative approach first proposed by Greg Ward in which a mirrored ellipsoid reflects light that has been transmitted through or reflected off of a sample into a digital camera. The digital camera, either a charge coupled device (CCD) camera or an Indium Gallum Arsenide (InGaAs) near infrared camera, has been calibrated as either a photometer (CCD) or radiometers (CCD and InGaAs) to measure the luminance or radiance emerging from window samples as a function of the angle of incident radiation and the angle of emerging radiation. A simple schematic of the device is shown below. My thesis describing this research is available from the MIT libraries and has also been published in the journals Lighting Research and Technology and Solar Energy.

The purpose of this research is to support the development of angularly selective, or light redirecting window systems that may have applications for improving daylighting or thermal performance of buildings. This new goniophoto/radiometer should provide major improvements in the time required for goniophotometric or gonioradiometric analysis of fenestration systems. Another innovation of the device is its ability to analyze light redirection over a broader range of the solar spectrum. Using the InGaAs camera, which is sensitive to radiation of wavelengths between 900 and 1700 nm, the majority of the near infrared component of solar radiation can be observed and included in BT(R)DF assessment.

This material is based upon work jointly supported by the Massachusetts Institute of Technology and by the National Science Foundation under Grant No. 0533269. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation (NSF).