Spray Foam Insulation in Washington, DC

A Washington, DC row house leaks at every joint — the rim of the basement, the gap between the brick and the framing, around every duct boot in the basement ceiling, and especially at the roof deck. Spray foam is the only insulation that air-seals while it insulates, which is why it has become our default for DC envelope work. Our crews install closed-cell at the roof deck and basement walls, open-cell at interior partitions and party walls for sound, and a hybrid in basements where vapor management matters most. We pull DCRA permits, schedule inspections, and leave the job clean.

Where Spray Foam Wins in a DC Row House

Roof deck (unvented assembly): Closed-cell at 4-5 inches against the underside of the roof sheathing converts a vented attic into conditioned space. This is the single biggest comfort and energy win for any flat- or low-slope DC row house, and it eliminates the ice-dam risk on the rear shed-style roofs. Basement walls: 2-3 inches of closed-cell directly on the masonry walls cuts moisture migration and creates a permanent thermal break — critical for the half of DC basements that sit below the seasonal water table. Rim joists: 2 inches of closed-cell at the band joist closes the single biggest air leak in the building. Party walls: Open-cell foam in a furred-out cavity adds 4-6 STC points of sound damping between you and your neighbor.

Open Cell vs. Closed Cell — DC-Specific Guidance

Open cell foam is light, vapor-open, and a strong air sealer. We use it inside the conditioned envelope — party walls, sound-control walls, and interior partitions — because it lets the wall dry in both directions. Closed cell foam is denser, has nearly twice the R-value per inch, and is vapor-closed. We use it everywhere moisture is a concern: basement walls, crawl spaces, rim joists, and the underside of unvented roof decks. For most DC row houses we end up using both, sized to each assembly.

DCRA Permits & Historic Districts

We pull all DCRA permits in our name. For roof-deck spray foam in an unvented assembly we file the permit, schedule the rough and final inspections, and provide as-built documentation. For homes inside designated historic districts (Capitol Hill, Georgetown, Dupont, Mount Pleasant, Anacostia, and others), interior insulation work is almost always outside HPO's review jurisdiction — we keep all our work on the inside of the brick and never modify the visible exterior. If your project requires a venting change that does affect the exterior, we coordinate the HPO submission for you.