Insulation · Batts
Batt insulation, fitted cavity by cavity.
Batt insulation performs when it stays at full loft and maintains contact with the intended air barrier. That means cutting and splitting around wiring, plumbing and framing rather than compressing material or leaving voids.
At a glance
- Where
- Open walls, floors and ceilings
- Materials
- Fiberglass and stone wool
- Fit
- Cut and split around obstructions, never compressed
- Also
- Sound-control assemblies between rooms and floors
What it is
Batts are pre-cut blankets sized to standard framing. Each one is fitted to its cavity: trimmed to length, split around wiring, and notched around boxes and pipes, so the insulation fills the cavity at its full thickness.
A batt insulates; it does not stop air on its own. The assembly still needs its air barrier, and the batt needs to sit against it without gaps.
Material choices
- Fiberglass batts
- Familiar, efficient, and available in many thicknesses and R-values for standard framing.
- Stone-wool batts
- Useful where the specified assembly benefits from their density, fire resistance, water resistance, or acoustic properties.
How it is installed
Confirm the specified product
Match the cavity depth and the specified batt, and check that the framing is ready.
Fit each cavity
Cut batts to length and split them around wiring and plumbing, so nothing is compressed and no voids are left.
Keep contact
Keep each batt in full contact with the air barrier, including at the edges, top, and bottom.
Walk the coverage
Check every cavity before the wall or ceiling is closed.
Where it fits
- Exterior walls in new construction
- Open walls during a remodel
- Floors and ceilings between stories
- Interior walls and floors for sound control
- Cantilevered floors
- Pole buildings and commercial framing
Batts, BIBS or spray foam?
Each can be the right answer. The cavity, the air-control plan, and the performance target decide.
| Consideration | Batts | BIBS | Spray foam |
|---|---|---|---|
| Installation form | Pre-cut blankets fitted into each cavity | Loose fiberglass blown behind fabric | Two liquids sprayed in place that expand to fill the cavity or build a layer |
| Irregular-cavity fit | Cut and split by hand around wiring, boxes, and odd bays | Fills around wiring, plumbing, and irregular framing as it is blown | Bonds to and follows framing, penetrations, and irregular surfaces |
| Air-control role | Insulation only; the assembly needs its own air barrier | Insulation; air control is detailed separately unless a tested assembly says otherwise | Can provide insulation and air control together when the product and thickness suit the assembly |
| Available cavity depth | Sized to standard framing depths | Fills the full depth of the open cavity | Installed thickness is set by the product, the assembly, and the requirement |
| Inspection and verification | The fit is visible in the open wall before drywall | Density and fullness are checked before close-up | Thickness and coverage are checked before the work is covered |
| Common applications | Walls, floors, and ceilings; sound control | Open walls, floors, and ceilings with crowded or irregular cavities | Rooflines, rim areas, basements, crawl spaces, and pole buildings |
| Relative project complexity | Straightforward in regular framing bays | Fabric goes up first, then a blowing machine on site | A spray rig, protection of the surrounding work, and product-specific requirements |
Sound control
Cavity insulation can absorb sound energy inside a wall or floor assembly, but it does not “soundproof” a room by itself. The final result depends on the complete assembly—including layers, framing, sealing, doors and penetrations.
Gable and knee walls
This is not a batts-versus-foam contest. First find where the thermal and air-control boundary belongs.
Is the attic vented?
Then the boundary is generally at the ceiling plane. A knee wall or gable wall between living space and the attic is part of the enclosure.
Is the attic conditioned or unvented?
Then the boundary may move to the roofline, and the approved plans decide which walls are part of the enclosure.
Fibrous insulation in an enclosure wall?
Batts or BIBS in that wall need a durable, aligned air barrier.
Spray foam in an enclosure wall?
Foam can do both jobs when the product, thickness, substrate, vapor strategy, ignition or thermal barrier, and assembly are approved.
Built to the assembly. Installed for local inspection.
Thermal Shop works from the approved plans, the selected product documentation and the requirements adopted for the project's jurisdiction. We document installed depth or assembly details and coordinate questions before finishes cover the work.
Photos from our installers
Start your insulation project
Homeowners
Request a Free EstimateHow it works for homeowners
- Request a free estimate and tell us what you're working on and where.
- We look at the attic, the house, or the concern first, then recommend the material and give you options.
- We install the work you approve and clear the work area when the install is done.
Contractors
Request a BidHow it works for contractors
- Request a bid with your plans, specs, and the work you want priced.
- Insulation is priced on its own bid, separate from gutters and shelving.
- We schedule around site readiness and inspections, and clean up the work area when the install is done.