Hi everyone,

I'd like to initiate a discussion around two urban morphological models I've been working with in my research, both inspired by Ralph Knowles’ Solar Envelope: the Shading Envelope and the Solar Control Box.

The Shading Envelope

This concept, developed in hot arid contexts like Tozeur (Tunisia), defines the smallest volume necessary to shade neighboring buildings during critical summer periods. The envelope is generated based on solar cut-off times, determined by peak solar radiation hours, and shadow fences corresponding to the facades needing protection. Parametric tools were used to calculate radiation and construct the volume accordingly. The results showed a significant reduction in solar gains and increased urban density, suggesting this form could contribute to both climate mitigation and densification goals. [paper Link]

The Solar Control Box (SCB)

The SCB integrates two constraints: the Solar Envelope, which preserves winter solar access, and The Shading Envelope, which prevents summer overheating. The SCB is essentially the intersection space that respects both constraints. It helps urban planners generate climate-responsive morphological rules by ensuring that built forms neither block beneficial winter sun nor allow excessive summer radiation. The method enables the evaluation of total and partial satisfaction domains, supporting a flexible and context-specific approach to solar design.

These two models were tested in the city of Tozeur, which has extremely hot summers and a growing need for energy-conscious urban strategies. I am currently exploring the transferability of these envelopes to other hot climate regions—especially those facing increasing urban density and heat waves.

• Have you encountered similar approaches that combine solar access rights and shading needs into a single design framework?
• What are your thoughts on the relevance and practical implementation of these models in hot climates, particularly in dense urban contexts?
• Do you think that urban regulations could integrate envelopes like these as part of future planning codes?
• Are there examples where similar volumetric regulations have been successfully applied in your cities or regions?

Looking forward to your thoughts and experiences!