Are vented crawlspaces really a bad idea—and can you actually over-insulate a window frame? The crew gets fired up tackling two topics that refuse to die in building science conversations.

First up is crawlspaces. The boys dig into a bit of U.S. crawlspace history, what vented crawlspaces were originally intended to do, and why they so often fail to perform as hoped. They walk through what crawlspaces should and should not do, and why climate, moisture, and enclosure strategy matter far more than tradition.

Then Steve takes the lead on one of his favorite “dumb ideas”: over-insulating window frames. While improving window performance absolutely matters, the discussion makes the case that, except in very cold climates, obsessing over frame insulation can introduce new water-management risks—and distract from much bigger thermal priorities elsewhere in the enclosure.

Classic UnBuild It: strong opinions, real-world building science, and a reminder to focus effort where it actually moves the performance needle.

Pete’s Resources:

• Building America Solution Center – Crawlspaces
• BSI-115: Crawlspaces – Either In or Out
• LSU La House Crawlspace
• GBA Q&A on Window Frame Insulation
• Pete Yost on Thermal Buck