Designing for Discovery

Daylighting from Design through Operation at John Lewis Elementary School, Washington, DC

A primary design goal for the modernization of John Lewis Elementary School was to provide classrooms with ample natural light to reduce reliance on electric lighting, minimize energy consumption, and help boost students’ math and reading performance.₁

Early in the project’s design phase, we conducted daylight modeling using Climate Studio to determine the optimal design for daylighting throughout the year. Our targets for all regularly occupied spaces in the school were >55% Spatial Daylight Autonomy and <10% Annual Solar Exposure.

West Video - Daylight

The analysis results from our daylight studies were shared during our weekly design charrettes. We flagged underperforming spaces (in terms of both daylight distribution and glare), and we proposed design solutions to address them. Such continuous feedback loops helped to ensure optimal daylighting outcomes.

One year after the building opened, we conducted a post-occupancy evaluation (POE) to measure daylight conditions (distribution and glare). Data showed:

• The school has better daylighting than its previous building.

• The school is achieving and exceeding the daylight autonomy targets established by our models during the design phase.

Through our POE study, we were also able to compare the daylight illuminance data from on-site measurements with daylight computer modeling to answer two important questions: How reliable are our daylight modeling tools, including Climate Studio, and can we trust the results to reflect reality? We compared Climate Studio daylight modeling data against on-site measurement data by calibrating our models to the exact date and time of collection. The comparison revealed that our on-site measurements closely aligned with Climate Studio’s predictions. On-site measurements showed a slightly higher percentage of optimally lit areas and fewer underlit spaces.

To do an accurate comparison, it was imperative to identify a clear daylight target and include detailed information that mimics the building’s real-life condition and context. The process of designing, measuring, and validating further confirmed the benefits of daylight modeling to inform design. 

John Lewis Elementary School, Washington, DC

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1. Lisa Heschong, “Daylighting in Schools: An Investigation into the Relationship Between Daylighting and Human Performance Condensed Report” (Heschong Mahone Group, August 1999), http://rgdoi.net/10.13140/RG.2.2.31498.31683.