Blown-in insulation, and whether to blow it yourself
The bags and the blower are at the big-box store, and for some attics that genuinely is the right answer. Here is how to tell whether yours is one of them - and what a professional crew does that a rented hopper does not.
What is blown-in insulation?
Blown-in insulation is loose material - usually cellulose or fibreglass - fed through a hose from a hopper and distributed to an even depth over an attic floor, or densely packed into an enclosed wall cavity. Its advantage over batts is coverage: it flows around wiring, pipes and irregular framing instead of being cut around them, so it leaves fewer gaps. It is sold by the bag with a rented blower, which is why the decision here is genuinely DIY or not rather than which contractor.
Signs you need blown-in insulation
- The existing attic insulation is uneven, compressed, or shallow enough that joist tops are visible
- Your attic floor is crowded with wiring, junction boxes and pipes that batts would have to be cut around
- You have closed walls you want insulated without opening them up, which is a dense-pack job
- Previous batts were installed with visible gaps, folds or compression around obstructions
- You want to add depth over existing insulation without removing what is already there
- The house is older and the framing bays are irregular widths that standard batts do not fit
Seeing something not on this list? Browse insulation problems by symptom →
How blown-in insulation actually works
Air seal first - while you can still reach the ceiling
ENERGY STAR names the attic penetrations that matter: kneewalls, the attic hatch, wiring holes, plumbing and pipe holes, dropped soffits open to the attic, recessed lights, and the furnace flue chaseway. Loose-fill is air-permeable and buries all of them.
Watch forThe single most consequential mistake on this page, DIY or professional. Once the material is down, every seal you skipped is under a foot of fibre. Sealing is cheap now and expensive forever after.
Baffles at every eave, before any material moves
Rigid baffles hold the loose-fill back from the soffit vents so the soffit-to-ridge airflow path stays open. They cost very little and go in before the hose does.
Watch forBlowing deep at the perimeter with no baffles. Loose material slumps straight into the soffits, cuts the ventilation, and blocked soffit vents are a well-known route to ice damming and a damp roof deck.
Protecting fixtures and the flue
Recessed lights not rated for insulation contact get dams or covers. The furnace flue gets metal flashing and high-temperature sealant with the clearance the appliance requires - never ordinary expanding foam.
Watch forLoose-fill piled onto recessed cans. Fixtures not rated for contact can overheat when buried, and you cannot tell which type you have from the room below.
Setting depth markers
Markers are placed across the attic before blowing so depth can be checked as the work proceeds and audited afterwards. This is what turns "we blew it in" into a verifiable result.
Watch forNo markers. Loose-fill settles to some degree, and without a record you cannot tell normal settling from a job that never reached target depth in the first place.
Blowing to even depth, perimeter included
One person works the hose in the attic, another feeds the hopper below. The material is walked out across the whole plane, working back toward the hatch so nobody crawls over finished work.
Watch forDepth that fades at the edges. The perimeter is the hardest place to reach and the coldest part of the ceiling, so it is where a rushed job gets thin - and it is the last place you will ever notice.
Dense-packing closed walls
For existing walls, holes are drilled per bay, material is packed to a density that resists settling, and the holes are plugged and finished. Density is the whole job - under-packed cavities settle and leave a cold void at the top.
Watch forA wall job priced like an attic job. Dense-pack needs higher pressure, a fill tube, and one hole per bay including above and below fire blocking. Missed bays are invisible until an infrared camera finds them.
What does blown-in insulation cost?
Blown-in is among the cheapest ways to buy insulation performance, priced by coverage area and target depth. Big-box bags plus a rented blower are cheaper still on materials, but exclude the air sealing and baffles that decide the result. Dense-packing walls costs considerably more. See the Cost Guide.
See the full blown-in insulation cost guide - by material, size and region →
If the number is the problem, here are the ways people pay for it →
Insulation depth & savings tools → Check target depth for your climate zone before you buy bags or accept a quote.
HomeMatchup does not perform blown-in insulation. We match you with licensed local insulation pros for blown-in insulation. Free for homeowners — Get matched free · how we verify pros.
When blown-in insulation is the wrong call
When saying yes is the wrong move:
- The attic has not been air sealed and you are not going to seal it. Blowing loose-fill over an unsealed ceiling buries every penetration you needed to reach. You will get some benefit and permanently lose access to most of it. If sealing is out of budget this season, wait - do not spend the insulation money first.
- There is vermiculite, knob and tube wiring, or moisture up there. ENERGY STAR says vermiculite "may contain asbestos" and must not be disturbed unless lab-tested, classes pre-1930 knob and tube as a fire hazard in contact with insulation, and flags wet or mouldy insulation as a professional finding. Any one of the three stops a blowing job dead.
- The soffit vents are blocked and baffles are not on the plan. This is the specific failure mode of a rushed blown-in job. You will not see it, and you may find out about it as ice dams the following winter, by which time the material is in place and moving it is a removal job.
- You want it in an open, accessible wall you are already renovating. If the studs are exposed, batts or board go in faster and are directly inspectable before the drywall goes up. Dense-packing exists to solve the problem of a wall you cannot open. If yours is open, that problem does not apply.
- Your ducts and air handler are in the attic and leaking. Loose-fill on the attic floor leaves them outside the thermal envelope. You are insulating against a space that your own system is actively conditioning through its leaks, which is a different problem and needs a different answer.
- You want a vapour or air barrier out of it. Loose-fill is neither. It slows conduction and does very little to stop air movement, which is exactly why the sealing step is not optional. Anyone presenting blown-in as an air sealing measure is selling you the wrong thing.
Types of blown-in insulation
| Option | What it means for you |
|---|---|
| Cellulose | Recycled paper fibre, treated for fire resistance. Denser, packs well, and is the usual dense-pack choice for walls. |
| Blown fibreglass | Lighter, does not absorb water the same way, and is the common big-box attic product. |
| Sealing, then blowing | The sequence matters more than the material. Air sealing is what makes the depth pay. |
| Start from the symptom instead | Cold rooms, ice dams and inadequate depth each have their own diagnosis page in the Problems archive. |
Can I do this myself?
Reasonable to DIY
- Topping up an accessible, dry, hazard-free attic that has already been air sealed and baffled
- Installing the baffles yourself before the material goes in
- Adding depth over existing loose-fill that is clean and dry - no removal needed
- Setting depth markers so you can check your own work against the bag's coverage chart
Call a licensed pro
- Any attic with vermiculite, knob and tube, moisture staining, or no safe footing
- Dense-packing closed walls, which needs correct density, one hole per bay and a fill tube - under-packing is invisible and permanent
- The air sealing step, if you are not confident detailing the flue chaseway with metal flashing and high-temperature sealant
- Anywhere with bath, kitchen or dryer vents discharging into the attic, which must be corrected first
- Low-clearance attics where working the hose means crawling over joists with limited visibility
What to check when hiring for blown-in insulation
- What material, and what installed depth are you targeting? The answer should name the product and a depth tied to your climate zone. "The usual" is not an answer you can check afterwards.
- Is air sealing included, and which penetrations specifically? Loose-fill buries them all. This is the last opportunity to reach them and it should appear as a priced line, not an assumption.
- How many baffles, and at which eaves? A number, not a gesture. Blocked soffit vents from a blown-in job are common and the fix afterwards means removing the material you just paid for.
- How are you handling recessed lights and the flue chaseway? Dams or covers for fixtures not rated for contact; metal flashing and high-temperature sealant at the flue. Both are fire-safety details.
- Will you set depth markers and leave me a coverage record? It is your only way to distinguish settling from underdelivery a year later, and efficiency programmes typically want to see it.
- For a wall job - what density, and how many holes per bay? Dense-pack succeeds or fails on density. One hole per bay is often not enough where fire blocking splits the cavity, and a missed section is invisible behind finished drywall.
- What did you find in the attic before quoting? A contractor who can describe the existing depth, the ventilation state and where the vents terminate has actually been up there. One who cannot has not.
Blown-In Insulation near you
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Sources
Sources last checked
- Insulation Fact SheetU.S. Department of EnergyRetrieved 2026-08-04Federal guidance on insulation types, R-value, and where it matters.
- Occupational Employment and Wages — Construction TradesU.S. Bureau of Labor StatisticsRetrieved 2026-08-04Labor cost context for home-services trades nationally.
Sources for figures and claims on this page.
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