Blown in insulation, packed into cavities batts cannot reach
Blown in insulation is loose material driven into a closed cavity under pressure, which is how older Massachusetts and Rhode Island homes get insulated walls without anybody opening them up. No demolition, no whole-room drywall repair, and no guesswork about what filled in behind the studs.
Cavity fill, bay by bay
Every bay filled to the top corner. A batt stapled in by hand rarely gets there, and the gap it leaves is where the cold comes through.
The signs your walls were never insulated properly
An empty wall cavity rarely announces itself with a report. It shows up as a pattern a homeowner notices over a winter or two, and by the time someone calls about it the signs are usually already familiar.
One room that never catches up. Every other room reaches temperature and this one does not, no matter how the thermostat is set or how long the system runs.
An exterior wall cold to the palm in January. Press a hand flat against an outside wall on a cold night. A properly filled cavity keeps the interior surface close to room temperature. An empty one does not.
A draft at an outlet or switch plate on an outside wall. Cold air moving through an empty cavity finds the same electrical box openings the wiring runs through.
Snow that melts unevenly off the roof. Patchy melt in some areas and untouched snow in others usually traces back to heat escaping through gaps in the shell below, not the roof deck itself.
A house built before 1980 with no record of a retrofit. Wall insulation was inconsistent through that era, and if there is no invoice, permit, or note in the file, the safest assumption is that nobody has opened those walls.
None of these prove a wall is empty by themselves. Together they are a pattern worth checking, and a thermal camera run during the assessment settles the question directly, reading the actual surface temperature of the wall instead of guessing from symptoms.
Where blown in insulation goes
Loose fill works anywhere the cavity is closed or awkward, which in an older New England house is most places. We install it in exterior walls through small holes drilled in the siding or plaster, across attic floors, into floors over unheated garages and crawl spaces, and into rim-joist bays that were never insulated in the first place.
The wall application is the one people ask about. Read wall insulation for how the holes are placed and patched. For the floor above your head, attic work follows a different method, since depth there is poured rather than packed. Basements and the joists above them are covered under basement insulation.
What the crew is actually doing
- Locating and mapping every stud bay so nothing gets skipped or double filled
- Drilling a small port per bay, above and below any fire blocking
- Filling under pressure until the hose stalls, which is how density is judged
- Plugging and patching each port, siding replaced or plaster filled
Air sealing still happens first wherever it can. Filling a wall does not close the path where a wire runs up into the attic, and whole-home air sealing is what handles that.
Cellulose or fiberglass
Two materials cover almost every job. Neither is better in the abstract. The house decides, and the person who walks it should be able to tell you why.
Dense-pack cellulose
Recycled paper fiber treated for fire and pests. It carries roughly R3.5 per inch, it is heavy enough to hold its own density in a wall for decades, and it packs around wiring and pipe runs instead of folding over them. It is the default for closed wall cavities in this area, and it is what the program scope usually calls for on a dense-pack job.
The tradeoff is weight and moisture behavior. Cellulose absorbs and releases water vapor, which is fine in a wall that can dry, and a problem in one that cannot. That gets checked before anything is drilled.
Blown fiberglass
Spun glass fiber, roughly R2.5 per inch as loose fill. It weighs a fraction of what cellulose does, it does not hold moisture, and it is the usual pick for an attic floor where depth is cheap and load on the ceiling is worth watching. In a wall it needs careful density control, because underfilled fiberglass settles and leaves a void at the top of the bay.
Where a ceiling has a marginal structure or an attic is being brought up in depth rather than packed, this is often the right call.
How they compare
R-value per inch figures are the published typical values for each material. The right answer changes with the cavity, the framing, and whether the assembly can dry, so treat this as background and let the assessment settle it.
Dense pack is a technique, not a product
The phrase describes how hard the material is driven in, measured in pounds per cubic foot, not what is in the bag. Filled to the right density, loose fiber stops moving air through itself and stays where it was put. Filled loosely, the same material in the same wall settles within a few years and leaves a cold band along the top of every bay.
You cannot see the difference from inside the room, which is why installer technique matters more here than brand names do. The tell is the hose. A bay is finished when the machine stalls against its own back pressure, not when it looks full through the port.
If a previous contractor filled your walls and the rooms are still cold, low density is the first thing to suspect. Old material that has slumped can be removed and redone. See old insulation removal.
Every job we scope goes through the utility review first, so density and coverage are on paper before anyone drills. Start with the free home energy assessment, and see the full insulation services hub for how this fits alongside the rest of the shell. The towns we cover page lists where the crew works.
What decides the cost
Every wall job is scoped on the actual house, not a rate card, because the same square footage can mean very different amounts of work depending on what the crew finds once the assessment starts. These are the factors that move the scope, never a price.
Number of stud bays
More bays means more ports to drill, more material to move, and more plugs to patch when the crew is done.
Siding type, and how it comes off and back on
Vinyl and aluminum unclip cleanly for the fill and clip back into place. Clapboard and shingle are cut piece by piece and refitted, which takes longer.
Old material already in the cavity
A wall filled once before and settled has to be emptied before the new fill goes in, which is a full extra step ahead of the install itself.
Fire blocking inside the wall
A horizontal block partway up a bay stops the hose, which means a second port above it and double the drilling and patching for that bay.
Balloon framing
Older houses framed this way run a cavity straight up two full storeys instead of stopping at each floor, which changes how the crew has to access and fill it.
Scaffolding for a second or third storey
Upper bays that are not reachable from a ladder need staging set up before drilling can start.
The utility incentive scope
Mass Save or Rhode Island Energy program review sets what portion of the scope qualifies for the address, changing what the homeowner pays without changing the physical work required.
Install day, and what happens afterward
On install day
- 1
Bay mapping. The crew walks every wall from the inside and the outside and marks each stud bay, so nothing gets skipped and nothing gets filled twice.
- 2
Drill. A small port goes into each bay, placed above and below any fire blocking so the hose can reach the full cavity.
- 3
Fill to refusal. Material is driven in under pressure until the hose stalls against its own back pressure, which is the sign the bay is at the density it needs to be.
- 4
Plug. Every port is capped and sealed once its bay is done, before the crew moves to the next one.
- 5
Siding back. Vinyl and aluminum courses clip back into place over the plugs. Clapboard and shingle plugs are cut and refit so the wall looks the way it did that morning.
- 6
Cleanup. Drop cloths, ladders, and the fill machine come off the property, and the yard and any interior access points are left as they were found.
The long term
Dense-packed cellulose does not need maintenance. It is not a filter to change or a system to service. Once it is packed to the right density it stays there, holding its R-value for as long as the wall itself stands.
A few things are worth revisiting the wall for later. A siding replacement is a natural point to check the cavity while it is already open. A window retrofit that changes the rough opening can affect the bay around it. Water intrusion from a roof leak or a failed flashing detail can wet the material and needs to be tracked down and dried out, not insulated over.
Outside of those situations, the material in the wall is expected to outlast most of the other systems in the house, the furnace, the water heater, even the roof, without anyone needing to think about it again.
Frequently asked questions
In a wall, yes, small ones. Blown in insulation goes in through the sheathing, so on vinyl or aluminum a course is unclipped, the bays are filled, and the siding goes back over the plugs so nothing shows. On clapboard or shingle, plugs are cut and refit. Inside plaster walls the ports are patched and left ready for paint.
Blown in insulation packed to the right density holds. That is the reason dense pack exists as a technique. Material blown in loosely does settle, and walls filled that way in the 1980s are common across older Massachusetts and Rhode Island homes. Density is the variable to ask any contractor about.
Not until the wiring is dealt with. Live knob and tube is designed to shed heat into open air, and burying it is a fire risk that no insulation program will approve. If we find it during the assessment the wiring has to be retired or replaced by an electrician first, and we will say so before anything is quoted.
Most single-family houses are one to two days for the walls, depending on siding type and how many bays are blocked by framing. Blown in insulation in an attic floor is usually the same visit. You get the day count with the written scope, before the schedule is set.