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Insulating an existing wall is very different from insulating a new wall before the drywall goes up. The goal is to add insulation without creating a system that cannot be inspected, repaired, or trusted over time.

ISO offers two approaches for existing walls: drill-and-fill with blown insulation for projects where a minimally invasive retrofit makes sense, or opening the wall so the insulation can be installed with direct access to the cavity.

Why ISO Does Not Install Injection Foam

The injection foam marketed for existing walls is not the same product as the spray polyurethane foam used in open-wall construction. These injection products are commonly water-based resin systems that are mixed with a foaming agent and injected into closed wall cavities as a liquid or shaving-cream-like material.

That distinction is important. ISO does not consider these injection products to be a substitute for conventional spray polyurethane foam, and we do not install them.

Our concern is the long-term stability of the material. Published building-science literature identifies shrinkage as a concern with newer-generation aminoplast injection foams, with reported shrinkage varying by product. Older urea-formaldehyde foam systems are also well documented as becoming brittle, shrinking, and crumbling over time.

ISO's position is straightforward: we are not willing to install a water-based injection foam into a closed wall and leave the customer with no practical way to verify the condition of the material years later. We would rather use a retrofit method we can stand behind.

The Problem Is the Material — Not the Access

The issue with injection foam is not simply whether the material can reach the far side of the wall cavity. Injection foam is specifically designed to flow through Closed cavities.

The concern is what the material does after it has been installed and dried. When an insulation material shrinks, deteriorates or loses contact with the surrounding assembly, gaps can develop inside the wall. Those gaps reduce the insulation's effectiveness and are extremely difficult to correct without reopening the wall.

For ISO, that is not an acceptable tradeoff simply to avoid making access openings.

For many existing wood-framed walls, ISO can use a drill-and-fill method with blown insulation. Access holes are strategically placed in the wall, and blown fiberglass or cellulose is installed directly into the cavity.

The U.S. Department of Energy recognizes drill-and-fill as a method for insulating existing wood-framed walls and describes blowing cellulose or loose fiberglass through holes drilled into wall cavities.

• Uses proven blown insulation materials rather than injection foam
• Allows the insulation to be installed directly into the existing cavity
• Can work around wiring, plumbing, and other common wall obstructions
• Requires far less demolition than removing an entire wall
• Access holes can be patched after installation

Thermal imaging can be used to evaluate the wall before and after the retrofit. A thermal camera does not see through the wall or directly measure the insulation inside the cavity, but it can identify temperature patterns that may indicate missing or inconsistent insulation.

Used as a diagnostic tool alongside proper installation and access, thermal imaging can help identify areas that deserve additional attention and provide a visual comparison of the wall assembly before and after the work.

When Drill & Fill Isn't Enough

Some walls need to be opened. If the wall has significant damage, moisture concerns, extensive obstructions, unusual framing, or requires a complete inspection of the cavity, the most reliable approach may be to remove the sheetrock and expose the wall.

ISO can assist with the insulation portion of that process and coordinate with the removal and reinstallation of the sheetrock so the wall can be properly insulated and then restored.

Opening the Wall Gives Us Control

• The entire cavity can be inspected before insulation is installed
• Existing insulation can be removed when necessary
• Wiring, plumbing, and framing can be identified and addressed
• The insulation can be installed with direct visual access
•  The finished cavity can be verified before the wall is closed
• Sheetrock can be reinstalled after the insulation work is complete

Existing-wall insulation is an application where the easiest-looking installation is not always the best long-term solution. ISO does not install injection foam simply because it can be installed without removing drywall.

We offer drill-and-fill with blown insulation when a minimally invasive retrofit is appropriate. When the wall needs to be opened, we can assist with the sheetrock removal and reinstallation required to do the insulation work properly.

If you believe your existing walls are under-insulated, contact ISO. We can evaluate the construction and help determine whether drill-and-fill or a more extensive wall opening is the right approach.