Wall Insulation in Richmond, VA

Wall insulation is the hardest part of an older house to fix, because the walls are already closed. Many homes in Richmond's older neighborhoods were built before wall insulation was standard, and the cavities behind the plaster or drywall are empty or hold a thin, slumped layer. Those walls feel cold to the touch in January and radiate heat in August.

How to tell if walls are empty

We check by removing an outlet or switch cover on an exterior wall and looking into the gap with a light, by looking down from the attic into the top of the wall, or by drilling a small test hole in a closet. An infrared camera on a cold or hot day can show which bays are empty, though it is not a substitute for looking.

Dense-pack for closed walls

For closed walls, we drill holes about one to two inches across, either from inside through the plaster or drywall or from outside after lifting siding, and blow cellulose or fiberglass into each cavity with a tube at high density. Dense-packing fills the bay tightly so the material does not settle and leave a cold gap at the top, and it slows air movement through the wall. HomeGuide lists dense-pack cellulose at about $1.60 to $4.20 per square foot. Holes are plugged and patched; inside, the patch then needs paint, and outside the siding goes back over it.

Spray foam for open walls

When the studs are exposed during a remodel, addition or gut renovation, spray foam is an option. Open-cell fills a 3.5-inch 2x4 cavity for roughly R-12 to R-13 at HomeGuide's per-inch figures; closed-cell can reach higher R-values in the same space and stiffens the wall. Fixr lists spray foam in existing walls at about $3.15 to $7.50 per square foot and new construction at about $2.75 to $6.50. Pouring foam into closed walls is possible with special low-expansion products, but it carries a risk of bowing plaster and is rarely our first choice.

Older framing

Houses built around the turn of the last century, like many in the Fan, the Museum District and Church Hill, may have balloon framing, where stud bays run from the foundation to the attic without a break. That changes the job: we block the bottom and top of each bay before dense-packing so insulation does not fall into the basement, and those open bays are also air leaks worth sealing. Knob-and-tube wiring, which is still found in some old houses, should be evaluated by an electrician before walls are filled, and we will not insulate around live knob-and-tube.

Moisture in the walls

The 2021 Virginia code requires a Class II or III vapor retarder, such as kraft facing or latex paint, on the inside of exterior walls in Climate Zone 4, and does not allow polyethylene sheeting there, according to Henrico County's summary. In existing walls, we look for signs of water coming in from outside, such as rot at window sills or stained plaster, before filling cavities, because wet insulation in a closed wall dries slowly.