Physical Model Analysis Tools
OVERCAST SKY BOX
The Overcast Sky Box does exactly what you would think, simulating a completely overcast sky. The box is an 8' cube with the interior consisting of mirrored walls on all four sides and a translucent glass top which illuminates the space to re-create the evenly distributed illuminance cast by a cloudy day. We are able to collect the illuminance values from within the model with photocell sensors, which we then use as a baseline case as we make design decisions in addressing problem areas to attain satisfactory and even illumination levels.
The Heliodon tool is a computer software driven pivoting table with a reflected spot light placed at the appropriate angle casting light onto it. The table is capable of adjustment for model studies at any site longitude. The software allows us to pivot the model relative to the simulated suns direct light to reveal the sun penetration within the building envelope at any given time of day or season. With an on-board camera we then record these penetration patterns, allowing us to compare the results of analysis and track progress throughout the iterative design process.
Digital Modeling & Analysis Tools
ECOTECT is a diverse building performance analysis software package. We use ECOTECT to study solar patterns, and for its graphical user interface as a front end to the most scientifically validated, physically based daylight rendering and analysis tool, RADIANCE. We also use it to interface with the dynamic daylight simulation engine DAYSIM. Additionally, we use ECOTECT to interface with and graphically represent complex data from both RADIANCE and DAYSIM. Finally, ECOTECT’s weather tool provides some useful climate data in a clean graphical format.
RADIANCE & Desktop Radiance
“RADIANCE is a highly accurate ray-tracing software system for UNIX computers that is licensed at no cost to users for non-commercial use; commercial use licenses including distribution rights are available for a fee. Radiance was developed with primary support from the U.S. Department Of Energy and additional support from the Swiss Federal Government. It is copyrighted by the Regents of the University of California.” - Greg Ward, Radsite
We use RADIANCE in conjunction with ECOTECT to analyze daylighting and lighting designs in a digital environment. This allows detailed study of glare concerns as well as point in time that are keyed to a specific location’s sky condition.
“Daysim combines the backward raytracing software Radiance, developed by Greg Ward at the Lawrence Berkeley National Laboratory, with a daylight coefficients approach. The underlying sky model to calculate annual illuminance profiles is the Perez all weather sky model. A stochastic model from Skartveit and Olseth has been adapted to mimic the short-time-step dynamics of indoor illuminances based on hourly mean direct and diffuse irradiances. Annual illuminance profiles are coupled with user occupancy data to predict the annual use of electric lighting in a building zone depending on the lighting and blind control strategy.” - Christoph Reinhart, irc.nrc-cnrc.gc.ca
We use DAYSIM in conjunction with ECOTECT to analyze daylighting and lighting designs in a digital environment. This allows detailed study of annual spatial daylight performance that is keyed to a specific location’s annual climate data.
EQuest Energy Modeling Software
EQuest is a windows friendly front end for DOE2 building systems analysis software. The program can model and test a building to predict its energy usage and is useful for systems comparisons as well as life-cycle cost estimation. You can easily make changes to a building model after a baseline has been created. Related to daylighting, these modifications include adding window overhangs, changing glass types, rotating the orientation, adding electric lighting controls and manipulating schedules. In this example, a baseline was created to pass IECC 2003, with an Energy Efficiency Measure package compared to show possible savings due to daylighting and other strategies.
This program is designed to be used during the early schematic phase of building design. The program takes into account building heat loss, solar gain, ventilation, day lighting, and other load factors.