Wall Insulation for Florida CBS Homes: A Boca Raton Guide

Most Boca homes have empty walls

If your Boca Raton home was built before 2002, there's a strong chance your exterior walls are concrete block (CBS) with nothing in the cores. That was standard Florida construction for decades — block walls with empty cells, furred-out interior framing, and drywall.

Empty block cores mean your walls conduct heat straight in from the sun-baked exterior. South and west-facing walls in Boca can hit 110°F+ surface temperature by 3 PM, and that heat radiates inward all evening — which is why your AC runs until midnight in July.

The three ways to insulate a CBS wall

1. Fill the block cores (existing homes)

The cleanest retrofit for an existing CBS home is filling the block cores with closed-cell spray foam or a pour-in insulation. We drill small access holes, fill each core, and patch. The result: an R-value boost plus a moisture barrier inside the wall — critical in coastal Boca where wind-driven rain soaks block.

This is the method we use most on mature Boca neighborhoods like Royal Oak Hills, Boca Square, and Boca Del Mar.

2. Dense-pack the furring cavity

Many CBS homes have a ¾"–1½" furred cavity between the block and the drywall. Dense-packing that cavity with cellulose or foam adds an air seal and another layer of R-value without touching the block. It's the method when the block cores are already filled or inaccessible.

3. Continuous exterior insulation (new builds or re-siding)

If you're building new or re-siding, continuous exterior insulation (rigid foam or closed-cell over the sheathing) is the gold standard. It breaks thermal bridging at every stud and block web — the single biggest heat-loss path in a CBS wall. Nothing else performs as well, but it requires opening the wall.

What it costs

| Method | Cost per sq ft | Best for | |---|---|---| | Block core fill (closed-cell) | $3.00–$5.00 | Existing CBS homes, coastal moisture | | Dense-pack furring cavity | $1.50–$3.00 | Cores already filled, air-sealing | | Continuous exterior insulation | $4.00–$7.00 | New build or full re-side |

A typical Boca CBS home (2,000 sq ft of exterior wall) runs $4,000–$10,000 depending on method. The block core fill is the sweet spot for most existing homes — meaningful R-value, a real moisture barrier, and no demo.

Why this matters for your energy bill

Wall insulation is the most under-insulated assembly in South Florida homes. Everyone does the attic. Almost nobody does the walls. But in a CBS home with empty cores, the walls can account for 30–40% of your cooling load — more than the attic in some orientations.

Filling the block cores is often the single highest-ROI insulation project on an older Boca home, ahead of an attic top-up.

Get it spec'd right

Every CBS home is different — block size, furring depth, coastal exposure. We spec the right method on site with a FLIR inspection that shows you exactly where the heat is entering. Call (561) 654-7698 for a free inspection across Boca Raton, Delray Beach, Boynton Beach, West Palm Beach, and Parkland.