Ventilation as a preservation strategy for timber roof trusses: A multi-method assessment of microclimate in historical attic spaces

Ventilation is among the most effective methods for ensuring favourable indoor climatic conditions in buildings. This research study focused on analysing the impact of ventilation on the indoor climate of attic spaces in listed sacral buildings. The research consisted of microclimatic monitoring of attic spaces in three churches located in northern Slovakia, combined with dynamic ventilation simulations. The aim of the monitoring was to analyse and evaluate the microclimatic conditions in the attic spaces, refine the monitoring methodology, improve applied procedures, and optimise the system of continuous measurement of indoor environmental parameters. Based on the measured air temperature and air relative humidity, theoretical wood equilibrium moisture contents were derived to illustrate the spatial distribution of moisture and seasonal trends. In addition, air mixing ratios were calculated to enable the assessment of the air’s drying potential throughout the year. Dynamic simulations were conducted to evaluate the effect of ventilating historical attics by opening the church entrance doors under three levels of humidity load and in three locations characterised by different climatic conditions. The results of this multi-method approach demonstrated that the specific characteristics of attic environments arise from the complex interaction of climatic, operational, and structural factors. Under certain conditions—particularly during the spring period or in cases of high humidity load—ventilation can support the natural drying of timber roof structures. However, the findings also indicate that ventilation is not universally beneficial. Therefore, a responsive ventilation strategy that considers current weather conditions and the drying potential of outdoor air is recommended. Moreover, the identification of representative sunny and cloudy days revealed specific climatic conditions under which the drying potential is most pronounced. The findings of this study thus provide valuable recommendations for the sustainable preservation of centuries-old timber roof structures.