Polyiso "Roof" Insulation used in Crawlspace? - GreenBuildingAdvisor
Summary
The article discusses the potential use of polyiso roof insulation for crawlspace walls and rim joists, exploring its effectiveness and any associated concerns.
Why It Matters
Understanding the suitability of materials like polyiso insulation for different applications is crucial for energy efficiency and durability in construction. This discussion highlights practical considerations for homeowners and builders, particularly in specific climates like North Texas.
Key Takeaways
- Polyiso insulation can be used in crawlspaces without significant concerns.
- Local building codes may require an ignition barrier over foam insulation.
- Using recycled materials can be a cost-effective and sustainable choice.
Polyiso “Roof” Insulation used in Crawlspace? JBullard | Posted in Energy Efficiency and Durability on February 27, 2026 02:02pm Hi All, Would there be a downside to using polyiso “roof” insulation for crawlspace walls and rim joists, and for the rim joists inside the house? This is the type that would typically be for a TPO or other membrane roof. It’s 2.6″ thick polyiso, presumably R-15, and I can get my hands on some used that seems in good shape, for much cheaper than alternatives in-store, and with a higher R-value.I believe it is or is the same as Henry Closed Cell Poliso bonded to glass-reinforced felt. Would there be any concerns using it in an interior application? The materials themselves seem fire-resistant.For context, this will be an encapsulated crawlspace with a 14mil vapor barrier floor & walls (CMU walls), with the insulation inside the vapor barrier.Located in North Texas. Climate Zone 3A. Thanks, Answer GBA Detail Library A collection of one thousand construction details organized by climate and house part Search and download construction details Join the leading community of building science experts Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field. Start free trial Related Questions Crawlspace insulation correctly installed? Floors very cold in winter Venting and Dehumidifying a Crawlspace Green Insulation Product for Crawlspace Crawlspace wall insulation Replies Expert M...
