The mddl Housing Development Lab is an interactive workshop exploring how middle housing can support more sustainable, attainable, and complete communities. While housing sustainability is often framed around materials and energy performance, this session starts one step earlier by asking what we build and where. Through a hands-on case study, participants will explore how zoning, design, financing, approvals, and project viability shape whether middle housing actually gets built. Examples from mddl’s work across North America, including post-fire infill modelling in Jasper, will ground the session in real-world municipal contexts. Attendees will leave with a stronger understanding of the trade-offs involved in middle housing development and how policy, technology, and process innovation can help turn sustainability goals into viable homes.