How much can a building affect human health—and what happens when occupants become highly sensitive to their environment? In this episode, Steve and Pete are joined by retired building scientist and pulmonary physician Nathan Yost for a thoughtful discussion on Multiple Chemical Sensitivity (MCS) and its relationship to building performance.

Nathan shares insights from decades of experience working with clients dealing with chemical sensitivities, along with more recent medical understanding surrounding pregnancy, hormonal changes, and biochemical sensitivities. The conversation explores where building science intersects with health concerns, how indoor environments can influence occupant comfort, and what building professionals should consider when designing for sensitive individuals.

Steve also shares examples from recent projects where MCS concerns led to major changes in materials, specifications, and interior design decisions. The discussion even ventures into the controversial topic of electromagnetic fields and so-called “dead zones,” highlighting the challenges of balancing occupant concerns with evidence-based building practice.

It’s a fascinating conversation about the overlap between buildings, health, and the limits of what construction professionals can realistically control.

Pete’s Resources:
Helping People with Multiple Chemical Sensitivity
Medical Conditions Building Professionals Need to Know About
Prescriptions for a Healthy House (4th Edition)
NIH – Electric & Magnetic Fields
BuildingGreen – Building Design and EMF

Four listener questions. Four very different building science challenges. One highly technical episode.

Steve, Jake, and Pete tackle a collection of building puzzles that span foundations, roofs, wall assemblies, and moisture management. The discussion starts with expansive soils and why successful construction often depends on engineered foundation systems designed to accommodate soil movement. From there, the crew examines attic radiant barriers, where they work best, and why climate matters when evaluating their performance.

The conversation then shifts to a cold-climate stucco retrofit involving exterior rigid insulation, reinforcing a core building science principle: prioritize the four control layers in the right order—water first, airtightness second, drying potential third, and thermal control fourth. Finally, they unpack the risks of a “diaper wall” assembly, where moisture-sensitive materials become trapped between low-permeance layers, and discuss how weather protection and airtightness can reduce those risks.

A highly technical episode packed with practical problem-solving, building science fundamentals, and real-world application.

Pete’s Resources:

• Post-Tension Slabs for Expansive Soils
• Evolution of Foundation Design for Expansive Soils
• ORNL Thermal Performance Evaluation of Attic Radiant Barrier Systems
• Building America Solution Center – Attic Radiant Barriers
• EPA Moisture Control Guidance
• GBA – Vapor Profiles Help Predict Whether a Wall Can Dry

Do certifications, standards, and professional credentials actually lead to better buildings—or just more paperwork? Steve, Jake, and Pete tackle one of the more uncomfortable questions in the building industry: why so many standards fail to consistently produce better outcomes in the real world.

The conversation ranges from ASTM standards and manufacturer testing to architectural credentials and industry certifications, questioning where standards genuinely help—and where culture, habits, and resistance to change become the bigger obstacle. Steve makes the case that the industry’s biggest challenge may not be technical at all, but cultural.

The crew also digs into one of Steve’s standout ideas: “chase friction.” Instead of accepting inefficient details, weak processes, or recurring failures, the goal should be to constantly look for the points of resistance that reveal where buildings can improve.

It’s an opinionated discussion with a few disagreements along the way, but the central takeaway is clear: meaningful progress only happens through rigorous education—for both building professionals and clients alike.

Pete’s Resources:

• Treasure of the Sierra Madre clip
• ISO Construction Quality Standards
• Construction Education & Certifications
• Chasing Friction Article