Blown-In and Batt Fiberglass for Annandale Attics and Renovations
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Annandale sits along Little River Turnpike and Columbia Pike, and the houses behind those roads are mostly ramblers, split-levels and colonials from the 1950s to the 1970s. Fiberglass is what we blow into most of their attics. It is light, it is not paper-based, and one manufacturer's data sheet for blown fiberglass states negligible settling. It also comes in three forms that get mixed up on the web: blown loose-fill for attics, batts for open framing, and the BIBS blanket system, which is only for walls with the studs exposed.
Three kinds of fiberglass and where each one belongs here
Blown attic fill. Blown fiberglass runs about R-2.2 to R-2.9 per inch, and one manufacturer chart puts R-49 at about 17 in and R-38 at 13.25 in minimum. That is a lot of depth, so the baffles at the eaves and the height at the hatch matter.
Batts. They belong in open framing: an addition, a basement finish, a gutted kitchen wall. A high-density R-15 batt is 3.5 in and an R-21 is 5.5 in, matched to the framing depth.
BIBS and dense-pack. BIBS, the blow-in-blanket system, stretches fabric across open studs and blows fiberglass in behind it, at about R-15 in a 2x4 wall. It cannot go into a finished wall. Closed walls get dense-pack instead, drilled and filled without fabric, at a density set by the product data sheet, and manufacturers list figures from about 1.6 to 2.3 lb per cubic foot.
Fiberglass or something else: an Annandale rule of thumb
Blown fiberglass is a sound pick when
- The attic floor is large and open. Blown fiberglass covers joists and wiring in one pass, and the price band is the lowest we quote.
- The ceilings below are older plaster. Fiberglass is lighter per R-value than cellulose, which matters on lath.
- A room or wall is being gutted. BIBS or batts fill the bays before drywall goes up, with no drilling.
Look at other materials when
- Walls are closed and hollow. Cellulose dense-pack is the usual choice, and fiberglass dense-pack is a second option.
- The bays are simple and open. Batts are quicker and cost less than fabric and blowing.
- The attic holds the air handler or a maze of ducts. Spray foam on the roof deck moves it all inside.
- The area is a wet rim joist or crawl space. Foam is a safer choice than loose fiber.
Two fiberglass quotes for houses like these
1960s rambler off Little River Turnpike, 1,400 sq ft attic, plaster ceilings, settled R-19
The plaster ceiling below is what steers the choice. Blown fiberglass weighs less than cellulose for the same R-value, so we keep the load on the lath down. We seal the top plates, set baffles at the soffits, fit a ring of blocking around the hatch and blow to R-49, about 17 in deep. The blown-in attic band of $0.90 to $1.60 per sq ft comes to $1,260 to $2,240 for this footprint. It is a one-day job, and the depth markers stay in place.
1950s one-story house gutted to the studs, 2,000 sq ft of exterior wall
The walls are open 2x4 framing, so BIBS fits. We staple fabric across the studs, cut a slit in each bay and blow to full density, about R-15, then trim the fabric flush so the drywall crew can go straight in. It has to be covered by drywall or another approved finish, and it is never left exposed. At $1.50 to $2.50 per sq ft, 2,000 sq ft of wall is $3,000 to $5,000, over two days. Because the walls are opened, the renovation needs a Fairfax County permit, and the current energy code applies to the altered walls.
Fiberglass price bands for Annandale
Blown-in attic caps to R-49 run $0.90 to $1.60 per sq ft, and a typical 1,200 to 1,500 sq ft attic comes to $1,200 to $3,000. Fiberglass batts in exterior walls run $1.00 to $1.80 per sq ft. Open-cavity BIBS or drilled dense-pack in walls runs $1.50 to $2.50 per sq ft, and a whole-wall job runs $3,000 to $7,500. Garage ceilings in fiberglass run $1,000 to $2,000. We write these into the estimate line by line, with the depth or density we plan to hit.
Who signs off on permits
The county handles building permits for Annandale, since it has no town government. Fairfax County Land Development Services, at 12055 Government Center Pkwy, Suite 324, 703-222-0801, is the office. Blown attic fiberglass by itself is usually not a permit item, but the code leaves that to the building official, so we confirm with LDS before we start. Additions, wall removal, framing changes, finished basements and asbestos disturbance are permit triggers.
Pre-1978 paint, old wiring and attic checks
Holmes Run Acres is a National Register district of 1951-58 mid-century houses, and we have not verified that county design review applies. For any exterior detail there we ask LDS. In any pre-1978 house, drilling painted plaster falls under the EPA lead-safe rule, and we work that way. In the attic, non-IC recessed lights get 3 in of clearance, and vermiculite is left alone, because we assume it holds asbestos.
Annandale Fiberglass Questions
Does blown fiberglass settle the way cellulose does?
Much less. The manufacturer's data sheet for the blown fiberglass we use states negligible settling, while loose cellulose settles about 10 to 20 percent. Still, the thickness has to match the chart on the bag, so we count bags per 1,000 sq ft and measure depth at the markers. About 17 in gets you to R-49 with that product.
We are gutting an Annandale split-level basement. Should the outside walls get BIBS or batts?
Either works once the studs are bare. Batts suit straight, regular bays. BIBS is worth a look where wires, pipes and odd framing make a batt leave gaps, because the fiber fills around them behind fabric. Finishing a basement is permit work with Fairfax County Land Development Services, so we confirm the sequence with them and plan our visit for after the rough-in and before drywall.
My old attic insulation is gray and black. Is that mold?
Usually not. Dark streaks on fiberglass are filtration soiling: air moving through the gaps carries dust and soot, and the fibers trap it. It shows where the air leaks are, typically at top plates, wiring holes and the hatch. It does not mean the insulation cleans the air. We air seal those spots before adding a new layer, and we flag stains that look like a roof leak.
Is Kings Park part of Annandale?
No. Kings Park and Kings Park West are subdivisions in the Burke and Springfield area, so we serve them from our Burke page, and Fairfax County permits still apply. Annandale's own streets run along Little River Turnpike, Columbia Pike, Backlick Road and Annandale Road, with Sleepy Hollow Woods and Broyhill Crest among its neighborhoods.
Can you promise a Dominion Energy rebate on fiberglass?
No, and we do not quote a number for one. Dominion's Home Energy Evaluation program runs through participating contractors, and we found no published dollar amount for insulation. Ask us to check where the program stands when you request the estimate. We do not build a rebate into any price.
Comparisons and nearby fiberglass pages
If you are weighing fiberglass against foam, our honest comparison for Virginia homes lays out the numbers, and the blown-in attic guide covers Fairfax County attics. The Burke spray foam post is a useful read for Kings Park owners. For the full list of work in town open the Annandale page, or check service areas for neighboring communities.
Nearby, the Burke fiberglass page and the Falls Church fiberglass page cover the neighboring homes.
Other Insulation Options in Annandale
Blown fiberglass suits regular attic floors, but plaster ceilings and gutted walls in a Little River Turnpike rambler raise other questions. The page for each alternative is here:
Spray Foam Insulation in Annandale | Batt Insulation in Annandale | Cellulose Insulation in Annandale
