Development and Preliminary Validation of a Hygrothermal Chamber with Mass Monitoring Built from a Reused Oven

Experimental determination of the hygric properties of building materials often relies on costly equipment, limiting access in resource-constrained laboratories. This study presents the development and preliminary validation of a hygrothermal chamber with continuous mass monitoring, built from a reused laboratory oven. The system independently regulates temperature and relative humidity (RH) and continuously measures sample mass, using approximately €146 in components (excluding the oven). Its performance was assessed under three hygrothermal scenarios using six materials, with comparisons against a climatic chamber and saturated salt solutions. The mean absolute error (MAE) and root mean square error (RMSE) relative to the setpoints were 0.41 °C and 0.96 °C for temperature and 0.43 %RH and 1.30 %RH for relative humidity, respectively. The load cell could not reliably resolve the small mass changes of non-hygroscopic crushed glass. For a single Moabi wood specimen, comparison with a reference balance yielded an MAE of 1.26 and an RMSE of 1.38 percentage points of dry-mass water content (N=9), with a positive mean bias of 1.18 percentage points. The chamber offers a promising low-cost platform for preliminary hygric experiments, although further validation is needed. Sorption isotherms, water vapor permeability and moisture buffer value remain to be determined.