Blown-in insulation is loose cellulose or fiberglass fiber blown through a hose. It goes in two ways: spread across an attic floor to a set depth, or packed hard into closed walls, floors and ceilings through small holes, which is called dense-pack. Which fiber gives more R-value per inch depends on which of those jobs it is doing. On an attic floor cellulose reaches a given R-value in fewer inches; packed into a wall, fiberglass does. Fiberglass is also lighter, settles less and is not ruined by a soaking. Either one performs only when the prep is right: air leaks sealed first, baffles at the eaves, dams at hot flues and recessed lights, and the full bag count the manufacturer’s chart calls for.
We blow cellulose and fiberglass into attics, dense-pack both into finished walls and floors, do the air sealing that has to go in before either, and take out the insulation that has to come out.
Types of loose-fill insulation
The Department of Energy’s renovation guide lists three materials blown as loose fill: cellulose, fiberglass and mineral wool, meaning rock or slag wool. It describes cellulose as recycled newsprint, finely shredded and chemically treated to resist fire, corrosion, fungal growth and vermin, and the Cellulose Insulation Manufacturers Association names the treatment — boric acid, working as both insecticide and flame retardant. The same guide rates blown mineral wool at R-3.7 per inch, and HomeGuide’s cost guide calls it costlier and less widely available than cellulose and fiberglass. We blow cellulose and fiberglass.
Open framing, before the drywall goes on, is a different job. The Department of Energy’s guide shows cellulose and dense-pack fiberglass blown dry into open bays and held with netting — a netted fiberglass wall is what the trade sells as a blow-in blanket, and Johns Manville’s brochure for the patented Blow-In Blanket System describes its fiber blown in dry behind that netting. The same guide lists sprayed-on fiber, mixed with water and adhesive at the nozzle and left to dry in the open cavity. Newer blow-in fiberglass skips the netting: Johns Manville’s current data sheet says the fibers lock into the cavity with no adhesive or netting and need no drying time at 10 percent moisture or less.
Cellulose vs fiberglass: where blown-in insulation differs
- R-value per inch. The Department of Energy’s renovation guide puts loose-fill cellulose at R-2.9 to R-3.4 per inch and loose-fill fiberglass at R-2.2 to R-2.7, so on an attic floor cellulose gets there in fewer inches. Dense-packed into a wall the order flips: the same table gives cellulose R-3.0 to R-3.4 and fiberglass R-3.6 to R-4.4, and the Department of Energy’s Building America Solution Center gives dense-pack cellulose R-3.2 to R-3.5 and dense-pack fiberglass R-4.2. Products vary more than the materials do: Owens Corning’s ProPink L77 chart reaches R-49 at 16 3/4 inches, about R-2.9 per inch, while Johns Manville’s Attic Protector needs 20.3 inches for the same R-49, about R-2.4.
- Weight and density. At R-49, GreenFiber’s cellulose chart calls for at least 1.6 pounds per square foot at 13.7 inches settled, about 1.4 pounds per cubic foot; Owens Corning’s fiberglass chart calls for 0.71 pounds per square foot, about 0.5 per cubic foot. At R-60 the two are 2.1 and 0.9 pounds per square foot. Weight matters on a thin or old ceiling: the residential code bars 3/8-inch drywall on a ceiling that has to support insulation, a footnote to Table R702.3.5 that reads the same in the 2024 edition New Jersey and New York adopted and the 2021 edition Connecticut uses.
- Settling. Loose fill compresses under its own weight, and the rating already counts it: the Federal Trade Commission’s R-value rule has loose-fill cellulose tested at its settled density (16 CFR 460.5) and every bag labeled with both the initial installed and the minimum settled thickness, the bags per 1,000 square feet and the minimum weight per square foot (460.12). GreenFiber’s chart goes from 15.2 inches blown to 13.7 settled at R-49, a 10 percent drop; Owens Corning says ProPink L77 shows negligible settling. What costs R-value is too few bags: the Department of Energy warns that insulation blown too light, which the trade calls fluffing, settles excessively and ends up below its label.
- Air movement. On an attic floor neither one is an air seal, and the energy code says air-permeable insulation shall not be used as a sealing material. Packed into a closed wall, both slow air a great deal: in lab tests Building Science Corporation published in December 2010, empty frame walls leaked 0.4 to 4 cubic feet per minute per square foot, and the same walls dense-packed with cellulose at around 3.5 pounds per cubic foot leaked 0.04 to 0.2 — an order of magnitude less, with results it called equally impressive from some blown fiberglass products. It counts neither as an air barrier material.
- Fire, mold and insects. Cellulose is paper, so it is sold treated: federal rules set flame-resistance, smoldering and corrosiveness tests and require a fire-safety label on every bag (16 CFR Parts 1209 and 1404), the residential code requires compliance with both (Section R302.10.3, 2021 and 2024 editions), and ASTM C739, the specification for cellulose loose fill, adds a fungi resistance test. The Department of Energy notes treated cellulose may still smolder if temperatures become hot enough, and lists blown fiberglass as non-flammable; Johns Manville’s data sheet for its blow-in fiberglass reports a pass with no growth on ASTM C1338, the fungi resistance test for insulation.
- Water. The Department of Energy warns that accidental wetting and high humidity can make cellulose absorb large quantities of water, reducing its thermal resistance, draining the fire retardant and creating a risk of mold and moisture damage. The Solution Center says cellulose breaks down when it gets saturated, while fiberglass will not be permanently damaged if it is saturated.
Which one we recommend
- Cellulose on an attic floor where depth is limited by a low roof at the eaves or a shallow attic, because it hits R-49 in 13.7 settled inches against 16 3/4 to 20.3 for the fiberglass charts above.
- Fiberglass on an attic floor over thin drywall or tired plaster, where weight is the worry; in attics that have had roof leaks, once those are repaired; and for topping up a deep layer of fluffy old fiberglass that a heavier material would compress.
- In a closed wall, either one, and we say which before we quote. Fiberglass gets more R-value into the same bay at dense-pack density: Johns Manville rates its blow-in fiberglass at R-15 in a 2x4 and R-23 in a 2x6 at 1.8 pounds per cubic foot, and Owens Corning at R-16 in a 2x4 at 2.2 pounds, against GreenFiber’s dense-pack cellulose at R-13 and R-21. Cellulose is the material the Department of Energy’s low-income weatherization programs favor, the Solution Center notes, and it can store small amounts of water; where a wall has had water in it, fiberglass is the safer fiber.
Blown-in attic insulation: how deep, and how to check it
ENERGY STAR recommends R-60 for an uninsulated attic in every climate zone we work in, and R-49 added on top where 3 to 4 inches are already there. Code for new work is R-49 in New Jersey and New York and R-60 in Connecticut; attic insulation covers the code and the eaves. The energy code rates blown insulation at the manufacturer’s settled R-value (Section R402.1.4), and each bag’s chart turns that into depth and bags:
- GreenFiber loose-fill cellulose, 19-pound bag: R-49 at 15.2 inches blown, 13.7 settled, 83.5 bags per 1,000 square feet; R-60 at 18.4 inches blown, 16.5 settled, 108 bags.
- Owens Corning ProPink L77 fiberglass, 32-pound bag: R-49 at 16 3/4 inches, 22.2 bags per 1,000 square feet; R-60 at 20 inches, 28 bags.
- Johns Manville Attic Protector fiberglass: R-49 at 20.3 inches, 28.4 bags per 1,000 square feet; R-60 at 24.3 inches, 36.2 bags.
To estimate a job, divide the attic floor area by 1,000 and multiply by the chart’s bags per 1,000 square feet. A 1,200-square-foot attic taken to R-49 from bare joists needs about 100 bags of that cellulose, about 27 of the Owens Corning fiberglass or about 34 of the Johns Manville. Bag weights and coverage differ by brand, so compare charts, not bag counts.
Where insulation is already there, run the arithmetic backwards. Measure the old layer in several spots and price it at the Department of Energy’s per-inch figures, R-2.2 to R-2.7 for old loose fiberglass and R-2.9 to R-3.4 for old cellulose: 8 inches of loose fiberglass is roughly R-18 to R-22. ENERGY STAR’s two recommendations land in the same place, near R-60 in total, so that attic wants roughly R-40 more, and the chart’s R-38 row is the nearest match: 12 inches of the cellulose above at 61.1 bags per 1,000 square feet, or 13 1/4 inches of the ProPink at 16.7 bags. Settled is not failed: a layer that has compressed still insulates at the thickness it now has.
Then check the work. The energy code has the installer fix depth markers to the trusses or joists, at least one for every 300 square feet, each facing the attic access, and post a signed, dated certificate listing installed and settled thickness, settled R-value, installed density, coverage area and the number of bags (Sections R303.1.1 and R303.1.1.1 in all three states). The Federal Trade Commission’s rule adds a receipt showing the coverage area, both thicknesses, the R-value and the bags used. Depth on its own proves nothing; the bag count held against the chart is the real check.
Before the first bag: sealing, baffles and dams
The Department of Energy says air moves right through fiber insulation, and that insulating an attic without air sealing it can make moisture problems worse. So the leaks close first: we pull the old insulation back and seal the wall top plates, wiring and plumbing holes, chases and dropped soffits, flue openings and the hatch. Its guide also says to have a contractor seal the ducts in an attic before cellulose goes in, so fibers are not drawn into the air distribution system — sealing duct seams by hand with mastic is part of our work, while new duct runs and equipment belong to a mechanical contractor. More in air sealing.
- Baffles at the eaves. With fiberglass or cellulose in a vented attic, the energy code requires a baffle at each soffit and eave vent that keeps an opening at least as large as the vent and extends over the top of the insulation (Section R402.2.4 of the 2024 IECC, R402.2.3 in the 2021 edition), and the residential code wants at least a 1-inch space at the vent and the sheathing (Section R806.3). ENERGY STAR calls blocking the flow of air at the eaves the most common mistake homeowners make.
- The hatch. Loose fill needs a wood-framed or equivalent dam so it cannot spill into the house or from higher to lower parts of the attic (Section R402.2.5.1 of the 2024 IECC, R402.2.4.1 in 2021).
- Recessed lights. Every bag of cellulose carries the federal caution: keep it at least three inches away from the sides of recessed light fixtures, do not place it over them so as to entrap heat, keep it away from furnace and water heater flues, and use a barrier to permanently maintain that clearance (16 CFR 1404.4). That label has no exception for IC-rated fixtures, so where cellulose goes in, every can light gets a metal dam, IC-rated or not; the label itself says to check with local building or fire officials on barrier requirements. ENERGY STAR’s rule for other insulation is the same three inches unless the fixture is rated for insulation contact. New fixtures are a third question: the energy code wants recessed luminaires in the thermal envelope airtight, IC-rated and buried in or surrounded with insulation (Section R402.5.4 and Table R402.5.1.1 of the 2024 IECC in New Jersey and New York; Section R402.4.5 and Table R402.4.1.1 of the 2021 IECC in Connecticut).
- Chimneys and flues. An interior masonry chimney keeps a 2-inch airspace to combustibles that may not be filled (IRC Section R1003.18), and ENERGY STAR notes that codes usually require 1 inch of clearance from metal flues. Both get aluminum flashing, high-temperature caulk and a metal dam before any fiber goes near them.
- Wiring and vermiculite. The Department of Energy says not to insulate over active knob-and-tube wiring until the house is rewired, and the EPA says to assume vermiculite — a pebble-like, pour-in fill, usually gray-brown or silver-gold — contains asbestos and to leave it undisturbed. Live wiring goes to an electrician first; vermiculite goes to a licensed abatement contractor, a trade we do not perform.
Dense-pack cellulose and fiberglass in closed walls and floors
Blown-in wall insulation in a finished house means dense-pack: the same fiber blown into a closed cavity much harder, until the bay is firm. The Building America Solution Center recommends 3.5 to 4.5 pounds per cubic foot for cellulose and 1.8 to 2.6 for fiberglass, several times the density either one sits at on an attic floor, and credits dense-pack with preventing settling, filling the cavity completely and slowing airflow. What that buys comes off the manufacturers’ own charts: at its 3.5-pound minimum GreenFiber rates dense-pack cellulose at R-13 in a 2x4 and R-21 in a 2x6; at 1.8 pounds Johns Manville rates its blow-in fiberglass at R-15 and R-23; Owens Corning reaches R-16 in a 2x4 at 2.2 pounds. The lighter wall settings on the Owens Corning chart, 1.25 to 1.75 pounds for R-14 and R-22 to R-24, sit below dense-pack density.
Drill and fill, from inside or outside
- Find out what is in the wall. A cut-out at an electrical box with the power off, or an infrared camera, shows empty bays, blocking and old batts. Deteriorated batts block the fill; the Solution Center’s answer is a 1-foot strip cut along the bottom of the wall to pull them out.
- Drill. The Solution Center describes 1- or 2-inch holes centered in each stud cavity about 6 inches below the ceiling, another below any blocking, and holes into the cavities over door headers, above and below windows and behind cabinets. The Department of Energy’s guide describes the outside route as a series of 2-inch holes through the exterior sheathing, with small pieces of siding removed to expose it.
- Fill to the manufacturer’s density, then scan again with the infrared camera before a single hole is closed.
- Close up. Inside: gypsum board or rigid foam plugs, joint compound, sanding and paint. Outside: the drainage plane and air barrier repaired, the holes plugged, the siding back on.
The Solution Center calls re-siding the ideal time to fill walls from outside, which also keeps drilling dust out of the rooms. Lath and plaster is the case for thinking twice. The Department of Energy’s guide says that to keep a plaster wall the best way to insulate is rigid insulation on the exterior, and that otherwise “you should probably leave the walls uninsulated and just do airsealing”: drilling from outside may break the plaster keys behind the lath and may also create moisture problems, and drilling from inside can damage the plaster, can disturb lead paint and produces a lot of dust. We say so when your house is one of those, rather than sell you the holes; wall insulation weighs the routes in full and insulation for older homes covers plaster houses.
What has to be settled before a wall is filled
- Knob-and-tube wiring. The National Electrical Code does not permit concealed knob-and-tube in hollow spaces of walls, ceilings and attics insulated with loose, rolled or foamed-in-place material that envelops the conductors (Section 394.12(5)), and the Department of Energy adds that drill and fill should not be used where knob-and-tube runs in the wall, because added insulation can push the wiring against the studs. An electrician replaces the live circuits first.
- Balloon framing. Stud bays that run unbroken from basement to attic need blocking at top and bottom before they can be dense-packed, per the Solution Center.
- Bays used as ducts. The Cellulose Insulation Manufacturers Association lists building cavities used as heating and cooling ducts among the reasons wall retrofits belong to professionals. A bay serving as a return air path stays empty.
- Water and paint. Building Science Corporation’s rule is to fix any rain leak before insulating, and it warns that a dense-packed wall keeps the cladding and sheathing colder and wetter longer, so paint problems are not uncommon on older buildings.
- Lead. Under the EPA’s Renovation, Repair and Painting rule, a firm paid to do work that disturbs paint in a home built before 1978 must be EPA- or state-certified and use certified renovators following lead-safe work practices. The EPA treats a job disturbing six square feet or less of interior painted surface, or 20 square feet or less outside, as minor repair and maintenance outside the rule; drilling a houseful of walls is well past that line. Ask every contractor you are quoting, us included, for the firm’s certification and the name of the certified renovator who will be on the job.
Floors, garage ceilings and cathedral ceilings
Closed floor bays fill the same way, and Owens Corning’s chart rates its blown fiberglass at R-30 in a 2x8 floor. A finished garage ceiling under a bedroom is one place we do it; see garage insulation. Under a crawl space floor, loose fiber needs netting to hold it and a crawl space that stays dry; see crawl space insulation.
Closed cathedral ceilings and flat roofs are the exception. Building Science Corporation calls dense-packing an unvented cathedral ceiling or flat roof a code violation that also fails the physics: a wall can dry to the outside, but shingles or a membrane stop a roof from doing the same. Those get a vented assembly, rigid board above the deck or spray foam under it; see roof insulation.
Blown-in insulation for sound
Fiber in a cavity absorbs airborne sound — voices, a television — and dense-pack has the advantage of filling the cavity completely. How much that buys is worth knowing before you pay for it. A trade bulletin for metal-framed partitions puts a wall with one layer of 1/2-inch gypsum board on each side at STC 30 to 35, credits insulation in the cavity with 4 to 6 points, and reports that structurally decoupling the two faces — resilient channel, staggered studs or a double stud wall — can reach STC 63 or more. The Cellulose Insulation Manufacturers Association says cellulose may be used to achieve STC ratings as high as 70 depending on the wall or partition assembly; that is the assembly talking, not the fiber. So filling an existing partition is worth the money when the complaint is ordinary household noise, or when the wall is open or being drilled anyway. If you want a room where the television next door is inaudible, the wall has to be rebuilt with mass and decoupling. Soundproofing insulation is work we do, in open walls and closed ones.
Top up the old insulation or take it out first
Dry attic insulation can usually stay, dirty or not. ENERGY STAR is blunt about the gray, grimy streaks homeowners worry about most: although the insulation is dirty, it is still okay to use, and there is no need to remove and replace. That gray is house dust filtered out of air leaking up through the ceiling, which makes it a map of where to seal. ENERGY STAR also says the new layer does not have to match the old: loose fill over batts, or unfaced batts over loose fill. The Department of Energy adds two cautions — a higher-density material should not go on top of a lighter one that compresses easily, and nothing goes over faced batts laid paper side up.
It comes out when it is wet, when mice have lived in it, when knob-and-tube wiring runs under it, or when the air sealing beneath it cannot be reached any other way. That removal is our own work, bagged under containment with a sealed HEPA insulation vacuum, and the deck is cleaned before anything new goes in.
Two things stop at our door. Mold on the insulation leaves with the insulation, but mold growing on the sheathing and rafters is a different trade — mold remediation, which we do not perform. New York licenses that work: its Department of Labor counts mold remediation on an area larger than ten square feet as a mold project, and beyond a small patch a licensed mold contractor goes first and we insulate after. Vermiculite is the other: the EPA says to assume it contains asbestos, to leave it undisturbed and not to attempt removal yourself, and that removal is licensed asbestos abatement, which we do not perform either.
Mice are a sequence, not a material choice, and borate treatment is not a rodent plan. Close the entry points and confirm the animals are gone first — the CDC organizes rodent work as seal up, trap up, clean up, and the trapping is pest-control work — then the soiled insulation of either kind comes out and the deck gets cleaned. New fiber blown over an active runway buys the job twice.
How the work goes, and the mess
Drop cloths run from the door to the hatch, the blowing machine stays outside and only the hose comes into the house. The prep above happens before any fiber goes in. Then the attic is blown from the eaves back toward the hatch, the order ENERGY STAR gives, to the depth markers and the bag count, and the certificate and the receipt stay with the house. Fiber reaches the rooms through the same gaps that leak air — recessed light housings, the hatch, gaps around duct boots — so sealing them first is what keeps the attic’s dust in the attic. ENERGY STAR advises a particulate respirator or double-strap dust mask for anyone working up there, and the Department of Energy says blown fiberglass must be fully enclosed to keep glass particles out of living space. On wall jobs the holes are the mess, one more reason to go in from outside when the siding allows.
What blown-in insulation costs
Most of our projects run between $3,500 and $12,500, moving with the attic area and the depth already there, the air sealing and details, the number of wall bays and how they are reached, and any removal first, which is our own line item.
National averages for blown-in alone run lower, so read them for what they include. HomeGuide’s blown-in cost guide, written 5 November 2025, puts blown-in attic insulation at $0.90 to $2.40 per square foot installed and a 1,200-square-foot attic at $1,100 to $2,900; it prices air sealing between the attic and the living space separately at $350 to $3,000, and puts dense-pack cellulose in walls at $1.60 to $4.20 per square foot of wall. HomeAdvisor’s guide, updated 17 June 2026, gives a normal range of $987 to $2,334 for a blown-in job. Neither is our price, and neither is a quote on your house.
Rebates exist through state and utility programs; see New York and New Jersey insulation rebates and Connecticut insulation rebates. The federal 25C tax credit ended for anything placed in service after 31 December 2025. For foam, see spray foam insulation cost.
Renting a blowing machine or hiring a crew
ENERGY STAR treats attic air sealing and insulating as do-it-yourself projects where the attic is accessible and not too difficult to move around in, and notes that some home improvement stores rent the blowing machine loose fill needs, though it says hiring a professional may be wise. HomeGuide puts machine rental at $100 to $200 a day, notes that some stores lend the machine free with a purchase of 10 to 20 or more bags, and calls it a two-person job: one feeding the machine, one on the hose. If you do it yourself:
- Do the prep above in that order, and dam every recessed light — under cellulose, the IC-rated ones too.
- Staple rulers to the joists and count bags against the chart for your R-value.
- Set the machine’s airflow as the manufacturer says; HomeGuide warns that setting it too high leaves the insulation overly fluffy, and once it settles the R-value may not be there.
- Wear a respirator, walk only on the joists, and work from the eaves toward the hatch.
Walls are a different job. The Cellulose Insulation Manufacturers Association says wall retrofits should be left to the professionals, and the Solution Center calls for a blowing machine holding at least 80 inches of water column at the takeoff and a feel for density that only comes with experience. A crew brings that, an infrared camera and the paperwork; a rental brings the lowest cash outlay.
Common questions about blown-in insulation
Is cellulose or fiberglass better for blown-in insulation?
Neither wins everywhere, and the answer flips with the job. On an attic floor cellulose needs fewer inches: the Department of Energy puts loose cellulose at R-2.9 to R-3.4 per inch against R-2.2 to R-2.7 for loose fiberglass. Dense-packed in a wall, fiberglass gives more, R-3.6 to R-4.4 against R-3.0 to R-3.4. Fiberglass also weighs about 45 percent as much at R-49, settles little and is not permanently damaged by a soaking; cellulose is treated with boric acid for fire and insects. On an attic floor, the air sealing and the bag count matter more than the choice.
How deep should blown-in attic insulation be?
Deep enough for ENERGY STAR’s R-60 in a bare attic, or R-49 added over 3 to 4 inches of existing insulation. By the manufacturers’ charts, R-49 is 15.2 inches of cellulose settling to 13.7, or 16 3/4 to 20.3 inches of blown fiberglass; R-60 is 18.4 inches of cellulose or 20 to 24.3 of fiberglass. With more than 4 inches already up there, measure it, count it at R-2.2 to R-2.7 per inch for old loose fiberglass or R-2.9 to R-3.4 for old cellulose, and blow the difference up to about R-60. Then check the depth markers and the bag count.
Does blown-in insulation settle?
Loose fill does, and the rating allows for it: the Federal Trade Commission’s R-value rule has cellulose tested at settled density, and every bag’s chart prints both the installed and the settled thickness. One cellulose chart goes from 15.2 inches blown to 13.7 settled at R-49, a 10 percent drop; one fiberglass chart shows negligible settling. What falls short of the label is insulation blown too light, with too few bags, which the trade calls fluffing.
Can you blow insulation into existing walls?
Yes, through holes. We drill each stud bay from inside or from outside behind the siding, dense-pack cellulose or fiberglass to the manufacturer’s density, confirm the fill with an infrared camera before anything is patched, and close the holes. Live knob-and-tube wiring, balloon framing without blocking, bays used as return ducts and walls with a water problem get settled first, and a lath-and-plaster house deserves its own conversation before anyone drills.
Can you blow new insulation over old insulation?
Usually. ENERGY STAR says loose fill can go over batts or older loose fill, that the types do not have to match, and that insulation gone gray and dirty is still okay to use, with no need to remove and replace. What stops a top-up is wet or mouse-soiled insulation, faced batts laid paper side up, live knob-and-tube wiring and vermiculite. Wet or soiled material comes out first, and that removal is ours; where mold is growing on the wood, a mold remediation contractor goes before us.
Is cellulose insulation a fire hazard?
Cellulose sold for homes must pass federal flame-resistance and smoldering tests and carry a fire-safety label, and the residential code requires both. The Department of Energy notes it can still smolder if temperatures become hot enough, which is why the label on every bag says to keep it at least three inches from the sides of recessed lights, never over them, away from flues, and behind a permanent barrier. That label has no exception for IC-rated fixtures, so under cellulose every can light gets a dam.
Can blown-in insulation get wet or moldy?
It can. The Department of Energy warns that wetting and high humidity can make cellulose absorb large quantities of water, lose thermal resistance and fire retardant, and risk mold; the Building America Solution Center says fiberglass is not permanently damaged by saturation. Fix roof leaks and any fan venting into the attic first. Soaked insulation of either kind comes out, and that removal is our work; mold growing on the sheathing and rafters is mold remediation, which we do not perform.
Does blown-in insulation need a vapor barrier?
Usually not in an attic. The residential code’s vapor retarder requirement is written for frame walls (Section R702.7), and the Cellulose Insulation Manufacturers Association says a vapor barrier is not recommended with cellulose in the United States except in high-humidity rooms such as pools or in very cold climates. Air sealing the ceiling matters more. A finished wall that gets dense-packed keeps the painted drywall or plaster it already has as its interior vapor control; nothing new goes on the inside, and the caution Building Science Corporation raises is on the outside, where the sheathing and cladding stay colder and wetter longer.
How much does blown-in insulation cost?
Most of our projects run between $3,500 and $12,500, depending on the area, the target R-value, the air sealing, walls versus attic and access. National averages for blown-in alone run lower: HomeGuide puts blown-in attic insulation at $0.90 to $2.40 per square foot, a 1,200-square-foot attic at $1,100 to $2,900, and dense-pack cellulose in walls at $1.60 to $4.20 per square foot of wall, with air sealing priced separately.
Can I blow in attic insulation myself?
In an open, easy-to-reach attic, yes: ENERGY STAR treats attic air sealing and insulating as do-it-yourself projects, and some stores rent the machine, which HomeGuide prices at $100 to $200 a day. Seal first, install eave baffles, dam the flues and the recessed lights — under cellulose, the IC-rated ones too — staple up depth rulers and count bags against the chart. Closed walls are a different job; the cellulose trade association says leave wall retrofits to professionals.
Blown-in insulation in New Jersey, Connecticut, the Hudson Valley and Long Island
Before we quote blown-in or cellulose insulation, we go into the attic and look at the walls: what is on the attic floor and how deep, what the walls hold, the leaks, lights, flues, fans and wiring, and any sign of water, pests or vermiculite. Then a written scope: what gets sealed, which material goes where and to what depth or density, how many bags, what has to happen first and who does it, and our price. The energy audit is free.
Call 914-825-6824 or use the contact form, 8am–8pm, seven days. The Home Insulators is family-owned, based in New Rochelle, NY since 2015, with a 100-plus-person in-house crew that never subcontracts. We work across all of New Jersey, all of Connecticut, New York’s Hudson Valley including Westchester, and Long Island; see our service area.