Cellulose Insulation in Alexandria, VA: Attics, Plaster and Tight Hatches

Alexandria's oldest blocks were platted in 1749, the Parker-Gray district is named for a school that opened in 1920, and Rosemont was developed between 1908 and 1941. Attics in houses like these tend to be small, awkward to reach and full of surprises, and that suits blown cellulose: the hose does the traveling, and the fill flows around joists, wires and chimney chases. It also has limits, and they matter more in an old house than a new one.

Two cellulose jobs, from first hatch to last plug

A Federal-era brick rowhouse a few blocks off King Street

Access. The attic floor is about 650 sq ft, reached by a narrow stair and a 24 inch hatch, with plaster-on-lath ceilings below and slumped batts around R-11 on top. The hose runs from the truck, so only the stair and the hall need protection, and the job is one day.

Order of work. We seal the chimney chase and top plates first. If the joist bays hold cloth-wrapped knob-and-tube wiring, we stop and bring in an electrician, because it cannot be buried. We also look at cracked plaster before loading the ceiling with a deep blanket.

Price. A cap to R-49 at $1.00 to $1.80 per sq ft is $650 to $1,170, with air sealing priced separately. Attic work is interior, so it sits outside what the city describes for the Board of Architectural Review, but a new roof vent would be an exterior change and we would ask first.

A 1910s Rosemont Foursquare with empty walls and a hip-roof attic

Walls. Roughly 1,400 sq ft of net wall area, and if the walls are wood frame with no fill, dense-pack is the retrofit. Most of the paint is older than 1978, so the work is lead-safe: drilling from outside through the siding with containment sheets, then patching every plug. We probe each wall with a moisture meter first, and where a bay is wet the cause gets fixed before any cellulose goes in. Dense-pack at $1.50 to $2.50 per sq ft is $2,100 to $3,500.

Attic. The space under the hip roof is about 800 sq ft and takes a cap at $1.00 to $1.80 per sq ft, or $800 to $1,440. All together, expect $2,900 to $4,940, over two days plus a patching visit. Rosemont is a National Register district, but that listing alone does not bring Board of Architectural Review review.

Limits that matter more in an old house

Why not fill a knee wall or sloped ceiling with loose cellulose?

Loose fill has nowhere to sit on a slope. Those spots, along with rim joists, damp crawl spaces and any place where bulk water or air is the problem, belong to spray foam. Cellulose is hygroscopic, so it takes up and releases moisture and is no barrier against liquid water. The remaining attic scope, including removal and sealing, is on our attic insulation page.

How deep is R-49 once cellulose has settled?

Settled cellulose delivers about R-3.2 to R-3.8 per inch, so R-49 is roughly 14 inches after settling, and cellulose needs about 3 to 4 inches less depth than blown fiberglass for the same R-value. Because loose fill settles 10 to 20 percent, we blow deeper than the target and read the settled figure off the bag chart. The attic floor is air sealed first, since ENERGY STAR calls for sealing before insulating and blown fill is not a substitute.

What changes for walls?

Dense-pack goes in through small drilled holes at 3.25 to 4.0 pounds per cubic foot, with no fabric and no demolition. Houses near Seminary Road, Duke Street and Mount Vernon Avenue get the same moisture test before any hole is drilled, and our wall insulation guide explains why payback on walls is slower than on attics. Open, exposed studs do not need dense-pack at all; they take batts or the fabric-retained system on the fiberglass page.

Frequently Asked Questions