Insulating Historic Delray Beach Bungalows Without Ruining Them

The challenge

Delray Beach's historic bungalows — the 1920s and '30s wood-frame homes east of Swinton — are beautiful, full of character, and almost completely uninsulated. They were built for cross-ventilation in an era before air conditioning, and their wall cavities and floors are often empty.

Modernizing their comfort without destroying their character — or trapping moisture and rotting them from the inside — requires a careful, materials-aware approach. You can't just pump foam into a 100-year-old wall and walk away.

The three rules for historic insulation

1. Don't trap moisture

Old wood-frame homes were designed to breathe. If you seal them too tightly with the wrong material, you trap moisture in the wall cavity and the wood rots. Every insulation decision has to account for vapor drive.

2. Preserve the character

We never recommend anything that requires removing original plaster, stripping interior trim, or altering the home's exterior appearance. The work happens inside the cavities or in the attic and crawl space.

3. Work with the existing structure

Knob-and-tube wiring (common in pre-1940 Delray homes) is a real constraint — you cannot insulate around active knob-and-tube. We coordinate with an electrician to evaluate and, if needed, decommission it before any wall insulation.

The approach we use

Attic: closed-cell foam + radiant barrier

This is the easy win. The attic is usually accessible, and closed-cell foam on the attic floor (or roof deck for a conditioned attic) plus a radiant barrier gives you the biggest comfort and efficiency gain with zero impact on the home's character. This alone typically cuts cooling costs 25–35%.

Walls: dense-pack cellulose

For the wall cavities, we use dense-pack cellulose blown in through small access holes (often from the exterior, behind cladding, or from interior through small holes that are patched). Cellulose is vapor-permeable — it lets the wall cavity breathe — and dense-packing eliminates air movement without sealing the wall shut. It's the right material for old wood-frame construction.

We do not use spray foam in historic wall cavities. Foam would trap moisture against old-growth wood and accelerate rot.

Crawl space: encapsulation

Most Delray bungalows sit on pier-and-beam. We encapsulate the crawl space (vapor barrier + sealed vents + wall insulation + dehumidification) so the floor stays warm, dry, and the home stops pulling musty air upward.

Windows and air sealing

Original single-pane windows are a huge heat path. We don't recommend replacing them on a historic home — instead we weatherstrip them, add interior storm panels (removable, invisible from outside), and air-seal around the frames. This preserves the home's look while cutting drafts dramatically.

What it costs

A full historic retrofit — attic foam + radiant barrier, dense-pack walls, crawl space encapsulation, air sealing — on a 1,200 sq ft Delray bungalow runs $9,000–$15,000. It's more than a modern home because the work is surgical, but the comfort and efficiency gains are transformative, and it preserves the home for another century.

The honest caveat

Historic homes are individual. Every Delray bungalow has its own quirks — previous renovations, patched wiring, modified framing. We always start with a full inspection (including a moisture survey and, if needed, an electrician's knob-and-tube check) before quoting. Book one and we'll tell you exactly what your home needs.