Pumice & Volcanic Aggregate Insulation
Naturally-formed lightweight mineral aggregate — pours like gravel, insulates like foam, lasts geologically.
Toxicity Screening — All Clear
This material screens clear across all seven independent toxicology authorities we use on every project.
Material Type
Natural Mineral Aggregate Insulation
Material Description
Pumice and similar volcanic-glass aggregates (pumice, scoria, perlite, vermiculite) form when gas-laden lava cools rapidly, trapping bubbles in solidified glass. The result is a naturally-lightweight, porous mineral aggregate that pours as easily as gravel but insulates roughly R-2 per inch and contributes significant thermal mass to the assembly. Volcanic aggregate insulation is common in dense-pack sub-slab applications, in concrete-mix admixtures (lightweight concrete), and in earthbag construction. The material is geologically stable — it's already millions of years old — chemically inert, fireproof, vapor-open, and doesn't support insects, rodents, or microbial growth. Vermiculite-specific note: pre-1990 vermiculite from Libby, Montana contained tremolite asbestos and should be tested before disturbance; modern South African and Chinese vermiculite sources are asbestos-free.
Composition & Origin
Health Profile — All Endpoints Clear
Severity scored 0–10 against the same 10 hazard endpoints we use for the chemical families on the avoid list. Every score is 1–2 — essentially no signal across every endpoint.
Common Forms & Brands
- Hess Pumice (mined Idaho)
- Perlite Institute member supplies
- Imerys vermiculite (modern asbestos-free)
- Common framing: loose-fill aggregate, lightweight concrete admixture, sub-slab insulating fill
Why We Use It
- Geologically stable — millions of years old as a material
- Chemically inert mineral content
- Fireproof — won't burn, won't melt at normal building temperatures
- Vapor-open and free-draining
- Doesn't support biological growth
Where It Performs Best
- Sub-slab loose-fill insulation
- Lightweight concrete aggregate replacement
- Drainage layer beneath foundation slabs
- Crawlspace and attic loose-fill applications
Building Applications for Pumice & Volcanic Aggregate Insulation
Listed alphabetically. Where in a home this material earns its keep.
Attic Loose-Fill (Perlite)
Crawlspace Floor Cover
Drainage Layer (Foundation)
Lightweight Concrete Mix Aggregate
Loose-Fill Wall Cavity Insulation
Sub-Slab Insulation Pour