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Blown In vs Batt
Quick answer: Blown-in (loose-fill) insulation flows around joists, wiring and odd shapes and is usually the faster way to add depth to an open attic floor. Batts are easier to handle without a machine and suit open wall cavities, floors and tidy, regular joist spaces. Both reach the same R-value when installed to the right depth.
The short version
Loose-fill is blown from a machine into a continuous blanket. Batts are pre-cut pieces of fiberglass or mineral wool that you lay or friction-fit between framing. In an attic floor with lots of obstructions, loose-fill tends to leave fewer gaps. In open walls during a renovation, or where you need to place insulation precisely, batts are often simpler. Many attics end up with both: old batts between joists and new loose-fill blown over the top.
Side-by-side
| Factor | Blown-in (loose-fill) | Batts |
|---|---|---|
| Best for | Open attic floors, topping up | Open walls, floors, regular cavities |
| Equipment | Blowing machine, hose | Knife, straightedge, stapler for faced |
| Coverage around obstacles | Fills gaps well when done right | Must be cut to fit; gaps common |
| Labour | Two people (one feeds, one blows) | One person can work |
| Settling | Some products settle; check bag | Little settling |
| Depth check | Depth markers required by many codes | Thickness printed on product |
| Mess | Dusty; cover openings | Less dust, but fibres irritate |
| Typical R per inch | ~2.2–3.8 depending on fibre | ~2.9–4.3 depending on density |
Gaps and installation quality
Insulation performs best as a continuous layer. Batts that are cut short, compressed around wiring, or leave gaps at joist ends can lose a meaningful share of their effective R. Loose-fill naturally fills those voids but can be blown too thin in hard-to-reach eaves or too fluffy, then settle. Both methods depend more on the installer's care than on the product. Walk the attic (on joists or boards) with a light after the job and check corners, eaves and around the hatch.
Over existing insulation
If the old insulation is dry, clean and not vermiculite, you can usually add more on top. For batts, use unfaced batts and lay them perpendicular to the joists so they cover the tops of the framing. Do not add a second vapour retarder above old insulation; it can trap moisture. For loose-fill, blow it evenly over the existing layer to the target depth. If old insulation is wet, mouldy, contaminated by pests, or is vermiculite, address that first; see attic insulation removal.
Cost considerations
We do not publish prices, but think about total cost per R per square foot rather than per bag or per roll. A cheaper product that needs more depth can cost more overall. Loose-fill often needs a machine rental, which some stores lend free with a minimum bag purchase; policies vary and change. Batts need no machine but take longer to fit well in a cluttered attic. Use the insulation cost calculator with your own prices.
Safety
Both products can irritate skin, eyes and lungs. Wear a well-fitting respirator rated for particulates, eye protection, gloves and long sleeves. Watch for nails through the roof deck, step only on joists or boards, and keep insulation clear of recessed lights and chimneys as product labels and codes require. See tools and PPE.
Worked example
Figures below are illustrative examples (2026-10-29), not quotes or guarantees.
Assumptions: 1,000 sq ft attic needing R38 added. With loose-fill at an assumed coverage of 40 sq ft per bag at R38 and 10% waste: 28 bags (see blown-in calculator). With unfaced batts rated R38 at an assumed 50 sq ft per package and 5% waste: 1,000 × 1.05 ÷ 50 = 21 packages (see batt calculator). Neither number is a real product's coverage.
Which to choose
- Choose loose-fill if your attic floor is crowded with wires, trusses and fixtures and you can get a machine and a helper.
- Choose batts if the area is open and regular, you work alone, or you are insulating walls or floors.
- Choose a pro if access is tight, the roof is low-slope, or you suspect vermiculite or other hazards; see DIY vs hire.
In walls
Open walls in a renovation are classic batt territory, but blown products can also be dense-packed behind netting or into closed walls through small holes. Dense-packing needs a specific technique and pressure; many homeowners hire a pro. Batts must be cut neatly around boxes and pipes, and split around wires rather than compressed behind them.
In floors over unheated spaces
Batts between floor joists over a garage or crawlspace are common. Support them with wires or netting so they stay in contact with the subfloor. ENERGY STAR lists floor targets by zone; see recommended R-value by zone.
Long-term performance
Both types perform for decades if they stay dry and undisturbed. Loose-fill can be moved around by wind wash at eaves or by people walking in the attic; check it occasionally and top up thin spots.
Quick test after the job
Look for even depth at markers, no gaps at corners, baffles clear, and insulation not touching heat sources.
Worked comparison, illustrative
Illustrative only: a 1,000 sq ft attic topped up by R-30. Loose-fill might need a stated number of bags from a bag chart and one day of machine rental with a helper. Batts might need unfaced rolls laid perpendicular to joists, with careful fitting around each obstruction, done by one person over a longer time. Your actual bag counts and prices will vary, so use the blown-in calculator and the batt calculator with your numbers.
Bottom line
Choose blown-in for fast, even attic top-ups and batts for open framing you can fit neatly. Air seal first either way, and record installed depth.
FAQ
Is blown-in better than batts?
Neither is always better. Both reach the target R when installed well.
Can I mix them?
Yes, loose-fill over batts is common in attics.
Does loose-fill settle?
Some does; the bag lists settled depth.
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