The Well Build Insulation Material Guide

This guide covers what to use, where to use it, and why the answer changes with your climate zone. It's drawn from the assemblies we specify on real projects, with the reasoning shown rather than just the conclusion.

What's inside

• Wall assemblies drawn layer by layer for cold, mixed and hot-humid climates — including what changes when there's little or no exterior insulation
• Roofs and attics: vented, unvented, and the condensation-control strategy each one needs
• Basements and foundation walls, insulated outside and in, and when interior is acceptable
• Our picks by category — batts, blown-in and rigid — with typical R-values, what each material tolerates, and which ones we reach for first
• Where fiberglass falls short, with the Oak Ridge testing behind it
• The six things that actually make an assembly mold resistant, in order
• Reservoir claddings, smart vapor retarders, and the details that decide which direction a wall can dry