How Much Energy Do Different Toplighting Strategies Save?

Abstract

Skylights can introduce considerable heat gains and losses that may offset the benefits of electric light savings and cause an increase in yearly net building energy use. The design of a toplight system needs to take into consideration different toplighting types, including aperture size and orientation, electric lighting control, and, most important, the local climate. This study examines the impacts of a variety of toplighting strategies and glazing types on the total yearly energy loads for a prototypical open office space situated in five different climates. Coordinated modeling with both an advanced daylight and electric lighting simulation program and a building thermal simulation program based on hourly weather data for an entire year enable the reliable estimation of annual lighting energy use in response to dynamically changing daylight conditions, and address the interaction between lighting energy and total building energy. This study shows that different toplighting strategies designed to meet a 2% daylight factor can save overall building energy consumption in a variety of climates, compared to the base case of an opaque roof, when electric lighting control is applied.