Today's show is about mysterious siding stains and air exchangers. Bill raises his concerns and clarifications about air quality as it is one thing that homeowners must start working with starting the fall season.

Reuben names and distinguishes the three types of mechanical ventilation: positive ventilation strategy, exhaust-only or point-source strategy, and balanced ventilation strategy. Tessa then adds the differences between these strategies, how they work and where they are most beneficial. She also discusses the multiple variables that affect the results when testing pressure and condensation inside the house. Bill and Reuben then share about interstitial condensation.

They talk about recommendations on how to manage and test mechanical systems such as ducts, ERVs, and HRVs. They also discuss the right settings for machines and systems.