R-Value
A measure of thermal resistance - how well a material prevents heat transfer. Higher R-values indicate better insulation.
Why It Matters for Homeowners
Why it matters: R-value is what the city checks on Title 24 plans before issuing a permit for any project that touches insulation. The right R-value depends on climate zone (LA spans zones 6 and 9, each with different requirements) and where in the home the insulation lives. Attics need higher R-values than walls. Per inch of thickness, closed-cell spray foam offers more R-value than fiberglass batts, but it costs significantly more.
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