Min Hall: Regenerative Building Materials to Design Out Waste
By The New Zealand Institute of Architects
TL;DR: Natural building materials offer regenerative solutions for construction, reducing waste by utilizing renewable resources and providing environmental benefits.
- Divert waste using renewable, reusable, and recyclable resources.
- Explore cob, adobe, and mycelium as sustainable alternatives.
- Test materials for shrinkage and ensure quality control.
- Employ hybrid systems and optimize for passive solar design.
- Achieve energy savings and pest resistance with natural builds.
Why it matters: Embracing regenerative building practices can significantly reduce landfill waste and energy consumption in construction.
Do this next: Perform a soil sieve analysis to assess local soil suitability for cob construction.
Recommended for: Architects, builders, and policymakers keen on implementing sustainable and regenerative construction methods.
Min Hall, FNZIA, EBANZ member, and lecturer at Unitec School of Architecture, presents at the June 5, 2025 'Designing Out Waste' workshop, outlining design and construction with regenerative natural materials to divert waste from landfills using renewable, reusable, recyclable resources. Emphasis on alternatives to wasteful products: cob mixes (15% clay, 10% sand, 75% straw, fibrous by hand-throwing), adobe blocks (stabilized with 5% lime, compressed at 2MPa), and mycelium composites for insulation (grown in 7 days, R-3.5/inch). Practical methods include on-site cob ovens for testing shrinkage <1%, prefabricated adobe for quality control, and mycelium bricks fire-tested to 1000°C. Benefits: zero-waste production (scraps composted), acoustic absorption (NRC 0.9), and hygrothermal regulation (RH 40-60%). Integration strategies: hybrid systems like light earth infill in timber frames (load-bearing up to 3 stories), detailing with limewash breathable finishes, and passive solar optimization. Hall shares longitudinal data from NZ builds: 25-year durability, 60% energy savings, pest resistance via borax treatments. Steps for practitioners: soil sieve analysis for cob suitability (>20% fines), block pressing with manual cinva rams, and certification paths under NZBC E2/AS1 amendments. Workshop insights include supply chains for hemp hurds, economic modeling (20% cost parity with stick-frame), and policy advocacy for natural material codes. This delivers concrete recipes, testing protocols, and project blueprints for scalable, waste-minimizing regenerative builds.