Most homes built before 1990 were constructed with little or no wall insulation. In the era of cheap energy, wall cavities were simply left empty — and millions of homeowners are still living with the result: cold rooms in winter, high heating bills, and walls that feel cold to the touch. Walls account for roughly 35% of a home's heat loss, making them one of the highest-leverage places to add insulation.
The challenge is that the walls are already finished. Drywall is up. Siding is on. The good news: you have options that don't require a full renovation.
Three Ways to Insulate Existing Walls
Most Disruptive
Option 1: Open-Wall Method
The open-wall method involves removing drywall or exterior siding to fully expose the wall studs, installing fiberglass batt insulation, then closing everything back up. This gives you the most complete coverage and works with any insulation type.
The downside: it's expensive, disruptive, and typically requires a significant renovation project. Most homeowners only consider this when they're already gut-renovating a room or replacing siding.
Moderately Disruptive
Option 2: Blown-In Insulation
Blown-in insulation (cellulose or fiberglass) is installed by drilling a series of holes along the top of each wall bay, inserting a hose, and blowing material into the cavity. No drywall removal required — just patched holes after the job is done.
The limitation: blown-in materials rely on gravity to settle into the cavity. They can leave gaps near fire blocks and horizontal framing members, and they settle further over time — reducing coverage and performance. Cellulose blown-in can also absorb moisture in wet climates.
Least Disruptive
Option 3: Injection Foam
Injection foam is drilled in through small holes in the siding (or through interior drywall in some cases), then injected as a liquid that expands to fill the entire wall cavity — including around fire blocks, wiring, and framing members. Once cured, it's completely stable and doesn't settle.
The advantage: it provides the most complete coverage of any non-demolition method, doesn't settle, and is safe around existing wiring. Holes are professionally patched after installation. Most jobs are done in a single day with homeowners staying in the house.
Side-by-Side Comparison
| Factor |
Open Wall |
Blown-In |
Injection Foam |
| Drywall removal required |
Yes |
No |
No |
| Fills entire cavity |
Yes |
Gaps likely |
Yes |
| Settles over time |
No |
Yes |
No |
| Disruption to home |
High — major renovation |
Moderate |
Minimal — one day |
| Typical timeline |
Days to weeks |
1–2 days |
1 day |
| Best for |
Major renovations |
Budget installs |
Occupied homes, best coverage |
Is Injection Foam Right for My Home?
Injection foam works with the vast majority of home types. A few signs your walls may need insulation:
- Interior wall surfaces feel noticeably cold in winter
- Electrical outlets on exterior walls feel drafty
- Heating bills are higher than expected for your home's size
- Rooms on the north or west side of the house are consistently colder
- The house was built between 1930 and 1985
Injection foam works through all common siding types:
Vinyl
Wood lap
Brick
Stucco
Cedar shake
Hardie board
Aluminum
In most cases, holes are drilled through the siding between courses, filled, and caulked after injection. The result is essentially invisible once painted.
What to Expect from the Injection Foam Process
1
Drill
Small holes are drilled into each wall bay through the siding. Hole size is roughly the diameter of a golf ball.
2
Inject
Foam is injected and expands to fill the cavity completely — including around wiring, fire blocks, and framing.
3
Patch
Holes are professionally patched and caulked. Most homeowners can't tell where the holes were after the job is complete.
Wondering if your walls are already insulated? We offer free quotes that include a wall cavity check — we'll tell you exactly what's (or isn't) in your walls before you commit to anything.
