Dew Diligence

Chances are that you have heard the old saying: “prevention is the best medicine.” That wisdom extends far beyond human health — fixing problems before they get out of hand is the best way to handle many of life’s issues. Homeowners will certainly recognize that this is true. Keeping up with some basic maintenance will keep many costly repairs at bay. Taking small steps like keeping windows caulked and applying pesticide when needed can prevent much bigger problems from cropping up down the road.

Out of sight, out of mind

However, not all problems are so obvious. In fact, some are hidden completely out of sight, giving no indication at all that there is a problem until it is already a major issue. Mold that forms behind the walls is one such issue. In many cases, the growth of mold can be remedied by simply sealing things up to keep moisture out. But how do you know if there is a moisture problem inside your walls that needs to be solved? Sure, you can take down the drywall and peek, but replacing your walls on a regular basis — likely for no good reason at all — is hardly a winning idea.

Fortunately, a team at the Department of Energy's Oak Ridge National Laboratory came up with a better plan. Their approach makes it possible to “see” through walls and determine how much moisture is present — no sledge hammer required. If something looks amiss, action can be taken. Otherwise, you can rest easy knowing that all is well without having to take any drastic actions.

Look beneath the surface

The team developed an approach that leverages microwave radar technology and works by emitting microwave signals that penetrate the layers of a wall and reflect back. When the microwaves interact with the different materials in a wall, such as drywall, insulation, and wood-based sheathing, their reflections carry information about the moisture levels in each layer. By measuring the time it takes for the microwaves to return to the sensor, the system can determine the distance to each layer and create a detailed moisture map of the wall. Mathematical algorithms analyze the characteristics of the reflected microwave pulses, allowing the system to quantify moisture levels with high precision, even behind drywall or cladding.

The system was experimentally validated by testing its ability to measure moisture in wood-based sheathing, a common material in home construction. Researchers used 10-millimeter-thick samples of oriented strand board, conditioned to specific moisture levels, and measured the moisture content using the microwave radar system. These results were then compared to readings from conventional handheld moisture meters, showing the radar system's accuracy to be within three percent. To simulate real-world conditions, the team tested the radar's ability to detect moisture through a layer of drywall placed 3.5 inches in front of the sheathing, which successfully confirmed its effectiveness.

This technology holds promise beyond walls, offering potential applications for roofs and foundations, and aiding in home inspections by identifying hidden moisture issues. Future research is anticipated to expand the system’s capabilities to work with a variety of building materials, including vinyl siding and brick. By enabling early detection of moisture problems, this innovation could help homeowners address minor issues before they escalate into significant problems, offering a proactive solution to protect both homes and health.