The Basic Principle Behind Injection Drying
Injection drying, sometimes called wall cavity drying or wall injectidry, works by forcing warm, low-humidity air into a wall cavity through small access holes, creating airflow that pushes moisture out through the porous surface of the drywall or, in some setups, out through a separate extraction point. The technique relies on the wall assembly itself — studs, insulation if present, and drywall — being able to release moisture through this induced airflow rather than requiring direct physical access to every wet surface. If cost is on your mind, how our pricing works breaks down what typically drives the number up or down. We've answered a lot of related questions on answers to common questions.
Where Access Holes Are Placed
Small holes, typically less than an inch in diameter, are drilled at baseboard level or through existing openings like outlet covers where possible, minimizing visible impact to the wall. Placement is planned based on the wall's structure — the location of studs and the direction air needs to travel to reach the wettest areas of the cavity. If you want to go deeper on this, our guide on LGR vs. Desiccant vs. Refrigerant Dehumidifiers: Which One Dries Your Phoenix Home? covers it well. We also break this down further in Relative Humidity vs. Specific Humidity: What Drying Techs Actually Measure.
What Makes a Wall a Good Candidate
Walls with clean water exposure limited to the lower portion, without saturated insulation that needs to be removed, are the best candidates for injection drying. Walls with wet fiberglass insulation are generally poor candidates, since compressed wet insulation blocks airflow and doesn't dry effectively even with forced air, making cavity removal the better option in those cases. For a related situation, see our post on Wet Insulation After Water Damage: Dry It or Replace It?. For background from an independent source, see the IICRC S500 restoration standard.
Monitoring Progress Without Opening the Wall
Non-invasive moisture meters that read through the drywall surface allow technicians to track drying progress inside the cavity without removing any material, checking readings daily until the wall reaches an acceptable dry standard and the injection equipment can be removed. the EPA's moisture control guidance has useful guidance on this if you want to read further. You can also review the Department of Energy's ventilation and humidity guidance for an outside perspective on this.