When wood-based thermal mass performs as well as concrete

Data for "When wood-based thermal mass performs as well as concrete" (awaiting publication). A full-scale experiment conducted to validate a theoretical approach for optimizing the distribution of internal thermal mass in concert with natural buoyancy ventilation. The ventilation is driven by the indoor temperature damping (which is produced by the thermal mass) and flows up during the night and down during the day. Two test buildings were constructed in Alabama, USA (ASHRAE climate zone 3A), to compare the performance of wood and concrete thermal mass in this temperature-ventilation cycle.

A first experiment was conducted from October 8 to November 8, 2022, in which one test building was fitted with concrete thermal mass panels, while the second didn't have internal thermal mass and served as a control. Another comparative experiment was conducted a year later, between October 8 and November 8, 2023, in which wood thermal mass panels were installed on the walls, floor, and ceiling of the empty test building, allowing a direct comparison with the concrete thermal mass in the other building. The sensor layout remained identical in both test buildings and across both experiments. A pair of ATMOS 22 ultrasonic anemometers measured the flow velocity and direction in the two pairs of ventilation chimneys, along with Apogee EE08-SS air probes to measure temperature and relative humidity. Three Apogee ST-110-SS thermistors measured the air temperature in the middle of the interior spaces at equidistant heights between the floor and ceiling. Hukseflux HFP04 foil heat flux and surface temperature sensors were installed on the back and front faces of the middle wall thermal mass panels, or directly on the exposed wall insulation in the empty control building. In the first experiment, two additional heat flux sensors were installed on the exposed floor and ceiling insulation of the building with concrete thermal mass and the empty control building. In the second experiment, those same sensors were moved to the exposed surface of the wood floor and ceiling thermal mass panels. Outside the test buildings, a Gill Maximet weather station monitored the ambient air temperature and relative humidity along with the wind speed, gust, and direction. A pair of Apogee SL-510-SS Pyrgeometer and SP-110-SS Pyrgeometer also measured incoming solar and infrared irradiance. All outdoor measurements were taken at roof level, in between the two test buildings.