The boys tackle four very technical building questions: expansive soils; attic radiant barriers; a cold climate stucco exterior rigid insulation retrofit, and a "diaper" wall assembly. For each of these 4 very different building issues there is at least one technical reference below.

Here is a brief lowdown on each question:

• building on expansive soils requires an engineered foundation and there are several building systems available to manage expansive soil;
• attic radiant barriers make the most sense in Climate Zones 1 - 3;
• follow the priority of the 4 control layers (water 1st, airtightness 2nd, drying potential 3rd, thermal last) and go with placing the WRB where you can get it the most continuous in the least complicated & expensive way;
• avoid configuring a diaper wall assembly (moisture-sensitive wall layer with very low vapor permeability layers on BOTH sides of this layer) whenever you can BUT the more the weather-protected said wall (so it "sees" very little moisture) and make it airtight, the less pressure there is on the vapor permeability of each layer in your assembly.

PETE'S RESOURCES:

• Post-tension slab for expansive soils: https://www.post-tensioning.org/education/tptapplications/slab-on-ground.aspx
• "Evolution of Foundation Design for Expansive Soils" https://ascelibrary.org/doi/pdf/10.1061/40960%28282%29/294?download=true
• ORNL "Thermal Performance Evaluation of Attic Radiant Barrier Systems" https://www.ornl.gov/publication/thermal-performance-evaluation-attic-radiant-barrier-systems-using-large-scale-climate
• Building America Solution Center - Attic Radiant Barriers: https://basc.pnnl.gov/resource-guides/attic-radiant-barriers
• EPA "Moisture Control Guidance for Building, Construction, and Maintenance" https://www.epa.gov/sites/default/files/2014-08/documents/moisture-control.pdf
• GBA "Vapor Profiles Help Predict Whether a Wall Can Dry" https://www.greenbuildingadvisor.com/article/vapor-profiles-help-predict-whether-a-wall-can-dry