Experimental Characterization of WiFi Signal Attenuation through Diverse Building Enclosure Materials

Accurately characterizing existing building envelope materials is critical for retrofit prioritization, yet current nondestructive testing methods remain expensive, equipment-intensive, and inaccessible for routine use. This study explored whether low-cost WiFi signal attenuation could serve as a practical screening indicator for identifying building wall assemblies. A Raspberry Pi-based sensing system measured the received signal strength indicator at 2.4 and 5 GHz across 10 distinct wall assemblies (8 campus buildings plus a controlled test box and an open-air baseline). Because each assembly was characterized by a single 3-min measurement run at one location, assembly identity is fully confounded with measurement location, and the analysis is therefore reported as exploratory and descriptive. On that basis, the grouping of measurement cases was associated with 92.5%–94.9% of the observed signal variance across both frequency bands, and 84.4% of case pairs were separated beyond a conservative Bonferroni-corrected threshold. Every wall case was separated from the open-air baseline by at least 18.7 dB. These results do not establish a validated method for identifying wall assemblies; rather, they present an initial low-cost measurement and analysis framework and quantify the magnitudes of separation. By requiring only a sub-$100 Raspberry Pi and a smartphone, this approach lowers the barrier for nonspecialist building assessment, contributing to the emerging paradigm of citizen building science in which ordinary occupants participate meaningfully in retrofit decision-making.