Yes, with the right technique. Drill-and-fill closed-cell foam through 1.5-inch access holes in plaster walls preserves the historic finish; a skilled plaster restoration specialist can make access patches invisible after final paint. Pre-1950 Hyde Park, Mariemont, Norwood, and Walnut Hills homes use this technique routinely.
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Cincinnati has substantial pre-1950 housing stock with plaster wall assemblies that constrain how insulation can be retrofit. Drill-and-fill is the technique that lets credentialed installers upgrade wall cavities without demolishing interior surfaces. The process: drill a 1.5-inch access hole between studs at carefully-spaced locations (typically one per cavity for cavities up to 8 feet tall, two per cavity for taller walls), insert a foam injection wand, dispense closed-cell foam to fill the cavity, then patch the access hole with a wood plug, plaster (for plaster-wall homes) or drywall mud, and color-match paint. The plaster-restoration step is what separates a high-end install from a basic one. A skilled plaster restoration specialist can make access patches invisible after final paint; a less-experienced crew leaves visible patches across every wall and devalues the architecture you are trying to preserve. Pre-1950 Cincinnati housing categories. (1) Lath-and-plaster walls (most homes built before 1940): wooden lath strips covered with three-coat plaster (scratch, brown, finish). Access holes can be patched with three-coat plaster and texture-matched to the original. Cost premium: $50-$150 per patch over standard drywall patching. (2) Wire-lath plaster (1920s-1940s): expanded metal lath replaces wooden lath. Patching is similar to lath-and-plaster but requires more careful cutting of the metal lath at the access hole. (3) Drywall with skim-coat plaster (post-1940): a hybrid where drywall is the substrate with a thin plaster veneer. Access patches use drywall techniques with plaster-veneer top coat. Foam choice for historic homes: closed-cell at 80-90 percent cavity fill (leaving room for plaster movement) is standard. Pure-fill closed-cell can stress the plaster as it cures and expands; the 80-90 percent target prevents this. Hybrid foam (closed-cell base + open-cell top-up) reduces blowout risk further but at slightly higher product cost. Cincinnati specialist installers who do historic-home work typically have 1-2 plaster restoration specialists on the crew or on call. Asking at quote time "who handles the plaster patching?" identifies whether the installer has invested in this capability or treats it as an afterthought.