7 Minutes of BS (#BuildingScience w/a BEAT)

In this episode of 7 Minutes of BS, we continue the discussion with engineer Jonathan Smegal of RDH Building Science Laboratories to break down the best exterior insulation retrofit systems based on real-world testing on five identical student housing units.

Jonathan walks through what separates a good system from a great one — fewer layers, less thermal bridging, lightweight claddings, and a dedicated air and water barrier at the sheathing layer. His preferred approach: remove the cladding, add sheathing if needed, apply an air- and water-barrier, then install exterior insulation with strapping on top.

Dan also makes the case for EIFS (Exterior Insulation Finishing Systems), which can be applied directly over existing brick — keeping thermal mass within the envelope, reducing landfill waste, and nearly eliminating thermal bridging when the foam is applied adhesively.

Key takeaways:

All five tested systems performed well for energy efficiency and durability

Fewer installation passes = lower cost and less complexity

Air and water control belong at the sheathing layer, not split across multiple materials

EIFS offers exceptional design flexibility and near-zero thermal bridging

Today, we are joined by Jonathan Smegal, an engineer with RDH Building Science in Waterloo, Ontario. Mr Smegal discusses the benefits of exterior insulation, then walks us through a recent study of five exterior insulation systems.

Dark roofs absorb heat, and light roofs reflect it.

Light roof shingles—combined with more insulation in the attic— can go a LONG way towards reducing the heat stress people in southern climates experience three seasons of the year.

Dr. Joe Lstiburek explains the fourth state of water: ADSORPED water. It exists on surfaces as tiny monolayers that can fill pores on the surface and cause mold. It also explains why expansive soils expand. If you thought you understood diffusion and capillarity, buckle up.

Vapor Diffusion Ports: Air Barriers That Let Moisture leave

Dr. Joe Lstiburek explains what Vapor Diffusion Ports are, how they work, why they're needed, and how to construct them—in about nine minutes.

The skinny version: they're like a modified ridge vent but for an unvented roof. They allow moisture to escape unvented roof assemblies without letting air leak out.