Microwave Radar For Moisture Detection

What if you could detect moisture in your walls without tearing anything apart? Find out how radar technology is changing home inspections.

Researchers at the Oak Ridge National Laboratory (ORNL), part of the Department of Energy, are using microwave radar to detect and measure moisture levels in walls without removing drywall or cladding. This method helps identify moisture quickly and allows for early treatment of mould growth.

A leaky seal

Most homes are built with wood-frame construction; when wood gets wet, it creates a perfect environment for mold. If a wall is damaged or improperly designed, water vapour can seep through the wood and dampen it. For this reason, the researchers explained, wood was chosen as the starting material to test the capabilities of microwave radar. Microwaves, part of the electromagnetic spectrum, interact with materials similarly to visible light but can penetrate deeper, creating reflections. Radar systems emit microwave signals and detect their reflections. In walls, the characteristics of these reflections depend on the moisture content of the materials.

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Measuring up

The team tested 305-millimetre-square wood sheathing samples, each 10 millimetre thick. The samples were dried in an oven and then conditioned to specific moisture levels. Using the microwave radar, the team measured the moisture content of the sheathing and compared these readings to those taken with a conventional handheld moisture meter. The proof-of-concept testing then advanced to the next phase—whether the radar could distinguish moisture levels in the sheathing. By applying mathematical algorithms developed by the ORNL team, the results confirmed that the radar signals could be linked to moisture content.

Beyond walls

Building on the promising results, the research team aims to license the ORNL technology to a manufacturer, making the portable microwave radar system available for purchase off the shelf. This would allow inspectors and homeowners to buy and use the device easily.

The tool could also assess roofs and foundations, helping potential homebuyers avoid unexpected issues by detecting problems that might be missed during a standard inspection. The following research phase will measure microwave reflections from complete wall assemblies with various claddings, including vinyl siding and brick.

Reference: Stephen Killough et al, Measuring the Moisture Content of Wood Sheathing with Continuous Wave Radars, 2024 IEEE Radar Conference (RadarConf24) (2024). DOI: 10.1109/RadarConf2458775.2024.10548546