Microclimate loggers: A matter of shielding… or wrapping?

Christophe Metsu, Stef Haesen , Sam Ottoy, Koenraad Van Meerbeek 

Direct sunlight can heat the sensor, housing, and shield of microclimate loggers overestimating air temperature readings as a result. This raises the question of how loggers should be shielded. We tested whether extra shield layers, ventilation holes inside the shielding and a wrap of aluminium foil around the logger housing reduce the error of one of the most commonly used microclimate loggers, the TOMST TMS-4, in open conditions. We hypothesised that a triple shield with holes combined with a wrapped housing would reduce the error most, and that this effect would be largest under sunny, high-radiation conditions. Over 41 days during summer 2026 in an urban context in Leuven, Belgium, we compared six new setups (single shield, triple shield and triple shield with holes, each with and without aluminium wrap) against an ultrafine-wire thermocouple (SurveyTag), using a mixed model with radiation and wind classes from a nearby weather station. We found that the aluminium wrap lowered the error by 0.33°C on average (95% CI 0.30 to 0.36), and its benefit grew with radiation intensity, from −0.06°C at night to 0.90°C in the very high radiation class. The best setups combined a triple shield (0.12°C to 0.13°C better than a single shield) with the wrap, whereas ventilation holes offered no significant benefit. On sunny afternoons, wrapping reduced the root mean square error by 35 to 40%. Wrapping the housing is therefore a low-effort and cost-efficient way to improve the accuracy of existing loggers in open ecosystems.