Short answer: yes. Most existing wood-frame walls can be insulated without removing the drywall or plaster. Dense-pack insulation, usually cellulose, is blown tightly into each wall cavity through small holes, either from outside (with siding removed or lifted) or from inside the room. The holes are patched afterward. Before starting, the wiring, the framing layout and any lead paint have to be checked, because those can change how, or whether, a wall gets filled.
I'm Joe Giordano. Since 2004 I've insulated a lot of older homes in Nassau and Suffolk, where walls with little or no insulation are common. Here's how dense-pack works and what to ask before you hire anyone.
What is dense-pack insulation?
Dense-pack is blown insulation installed at a high density, so the cavity is completely full and the material stays put. The U.S. Department of Energy's Building America Solution Center describes the process: decide whether to work from inside or outside, find the framing and blocking, drill or cut access holes, fill each cavity to the manufacturer's dense-pack density, verify every cavity is full, and patch the walls (DOE Building America guide).
Tightly packed cellulose also slows air moving through the wall cavity, which loose material doesn't do as well.
Should the holes be drilled from inside or outside?
Both work. It comes down to your house:
- From outside. A row of siding is removed or lifted, holes are drilled through the sheathing, the cavities are filled, the holes are plugged, and the siding goes back. This keeps the mess out of your rooms. It works well with vinyl, wood and other siding that can come off and go back on cleanly.
- From inside. Holes are drilled through the drywall or plaster, the cavities are filled, and the holes are patched. This can make sense when the siding is hard to remove, like brick, stucco or some older shingles, or when only a few rooms are being done.
Before any work starts, ask who handles patching, painting and siding. Get it in the estimate.
What needs to be checked before insulating walls?
- Knob-and-tube wiring. DOE's guide notes that the National Electrical Code doesn't allow insulation to be applied to or surround knob-and-tube wiring. If your house has it, an electrician needs to deal with it first.
- Lead paint. Many homes built before 1978 have lead paint. Drilling or cutting painted surfaces disturbs it. EPA's lead renovation rules set requirements for that work, so ask any contractor how they handle it.
- Moisture. Signs of leaks, rot or water staining in the walls need to be fixed first. Insulation shouldn't go into a wall that's getting wet.
- Framing and blocking. Fire blocking, windows, diagonal bracing and older framing create cavities of all shapes. Each one needs its own hole, or it gets missed. A thermal camera helps find the empty bays before and after.
- What's in there already. Some walls have old, slumped batts or partial fill. Dense-pack can often still go in, but the plan changes.
Is dense-pack worth it in an older Long Island house?
If the walls are empty or nearly empty, filling them usually helps rooms feel less drafty and more even. Walls are only part of the picture, though. In most homes I'd look at the attic first, because it's often the easier, bigger fix. I'll tell you which comes first for your house. For houses with historic details, see insulating historic homes.
Is cellulose the only option for existing walls?
No. Fiberglass can also be blown at high density. Some contractors inject foam. Spray foam generally needs open walls. Each has trade-offs, covered in cellulose vs spray foam and wall insulation options.
What happens at the free estimate?
I walk the house, check the walls with a thermal camera to see which cavities are empty, and look at the siding, the wiring I can see, and the attic and crawl space. Then I tell you whether I'd go from inside or outside, how the patching would be handled, and what I'd do first.
Frequently asked questions
How big are the holes?
They're small, just big enough for the fill tube. The exact size depends on the method and equipment, and I'll show you before we start.
Does dense-pack settle?
When it's packed to the manufacturer's dense-pack density, the material fills the cavity tightly and resists settling. That's the point of packing it dense.
Does it help with noise?
Filled walls usually cut some outside noise. For soundproofing goals, see our soundproofing page.
Do you work in my town?
We work across Nassau and Suffolk, including Huntington, Smithtown, Hempstead, Oyster Bay and the Nassau County area. See our service areas.
Get your walls checked
Call or text me at (631) 492-0214, Monday to Saturday, 7 AM to 7 PM. I answer my own phone and call back the same day. Or request a free estimate. Read more about our wall insulation and blown-in insulation work.