Optimization of Roofing Systems for Daylighting

Thursday, April 18th: 8:30-10:00 AM

Presenter: Ladan Ghobad, North Carolina State University, Raleigh

Forum Topic:  Optimization of Roofing Systems for Daylighting

Overview of the roofing system concepts (Wayne Place)

• Lighting philosophy
  • Quantity
  • Quality
  • Psychological issues
• Thermal philosophy
• Structure
• Systems integration
• System configurations

Radiance lighting simulations (Ladan Ghobad)

• Average illuminance on the task surface
• Variations in illuminance on the task surface

Comparison of Radiance predictions and experimental illuminance measurements (Christoph Konradi)

Predictions of annual lighting electricity savings based on DaySim (Ladan Ghobad)

Annual lighting simulations based on experiments (Jianxin Hu)

Whole building energy analysis using EnergyPlus (Ladan Ghobad)

Overall energy optimization of Roofing Systems for Daylighting (Ladan Ghobad)

Brief summary of results:

An investigation has been made of potential lighting electricity reductions and associated thermal impacts of replacing electric light with daylight admitted through rooftop glazing. Horizontal apertures on flat roof (skylights) and vertical apertures facing in two opposite directions (roof monitors) are examined in a prototype office building. A computer simulation tool that integrates lighting simulation and energy simulation called DIVA-for-Rhino has been used. Building operation costs are calculated as a function of aperture to floor area so that the optimum roof daylighting design could be identified. The results indicate that rooftop glazing contribute to savings in building operation if a modest amount of glazing is used in the roof. The design implications of the results are discussed and important parameters that influence the rooflit building operation costs will be outlined.