Cellulose Insulation for Arlington's Closed Walls and Slumped Attics

Most Arlington houses we walk into have finished walls and old attic insulation that has seen better decades. The bungalows and Colonial Revivals of Ashton Heights, the Craftsman houses of Lyon Park and the Cape Cods around Cherrydale all have plaster or drywall over frame studs. Cellulose is how we insulate them without demolition, dense-packed through small holes or blown loose over an attic floor, and our crews reach them along Columbia Pike, Arlington Boulevard and Wilson Boulevard.

Good fit and steer-away, side by side

Good fit

• A closed 2x4 wall you do not want to open. Dense-packed cellulose gives about R-3.6 to R-3.8 per inch, so a 3.5 inch cavity ends up near R-13, and the 3.25 to 4.0 pounds per cubic foot density is meant to leave no voids.
• An attic floor cluttered with bath-fan ducts, wiring and irregular joist bays, where the hose reaches what a batt cannot.
• Slumped batts that are still dry: an overlay adds depth without pulling anything out.

Steer away

• Framing that is already exposed, where batts or the open-cavity method on our fiberglass page cost less.
• Rim joists, crawl spaces and knee-wall slopes, which need the air and moisture barrier that spray foam supplies.
• Any roof leak or damp wall. Cellulose is hygroscopic, holding and releasing moisture, so it never goes over a leak. Our attic comparison lays out the trade-offs.

Before any fiber goes in

Blown fiber is not a substitute for air sealing, and ENERGY STAR says to seal leaks in the attic floor before adding insulation, so we start there: top plates, wire and duct penetrations, the gap around the chimney chase. Baffles go in at every eave bay to hold the 1 inch airflow space under the roof deck. Loose fill in an attic settles roughly 10 to 20 percent over time, so we compare settled depth against the bag label rather than the depth on install day. If an attic holds vermiculite, EPA says to assume it is asbestos and not to disturb it, and the job stops until a professional has looked.

Scoped and priced: an Ashton Heights bungalow and a Lyon Village attic

Ashton Heights bungalow, about 900 sq ft of closed wall

A 1,200 sq ft Craftsman-style bungalow has empty 2x4 walls under plaster, and a low attic over about 600 sq ft that holds a thin, flattened layer. Dense-pack at $1.50 to $2.50 per sq ft on 900 sq ft of net wall is $1,350 to $2,250. A cellulose overlay on the attic at $0.70 to $1.20 per sq ft is $420 to $720, and the two together come to $1,770 to $2,970.

On a house this age the details decide the day. Painted plaster means lead-safe setup before a single hole is drilled. Horizontal blocking inside the wall means extra holes, one above and one below each block. Any knob-and-tube wiring stops the job until an electrician has looked, because it cannot be buried in insulation. If the walls test dry and the wiring is modern, expect one day for the walls and a few hours for the attic. The holes are plugged and left ready for your patch and paint.

Lyon Village Colonial Revival, 1,000 sq ft attic floor

A two-story house of about 1,800 sq ft has an attic floor with R-19 batts that have slumped and been disturbed by decades of wiring work. If they are dry, an overlay is $0.70 to $1.20 per sq ft, which is $700 to $1,200. If sections are wet, matted or fouled and have to be pulled first, a full cap at $1.00 to $1.80 per sq ft runs $1,000 to $1,800.

The crew works from a small hatch and a hose run from the truck, so nothing heavy is carried up the stairs. Recessed lights in the ceiling below need to be rated for insulation contact, or they get a dam that holds the cellulose 3 inches away. The bath fan duct is checked and clamped to the roof. Depth markers stay behind, and the job takes one day.

Frequently Asked Questions