Citation: Metals, M.; Palcikovskis, A.; Borodinecs, A.; Lesinskis, A. Typology of Latvian Churches and Preliminary Study on Indoor Air Temperature and Moisture Behavior. Buildings 2022, 12, 1396. https:// doi.org/10.3390/buildings12091396 Academic Editor: Ricardo M. S. F. Almeida Received: 12 August 2022 Accepted: 2 September 2022 Published: 6 September 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). buildings Article Typology of Latvian Churches and Preliminary Study on Indoor Air Temperature and Moisture Behavior Martins Metals *, Arturs Palcikovskis, Anatolijs Borodinecs and Arturs Lesinskis Department of Heat Engineering and Technology, Riga Technical University, Kipsalas Street 6, LV-1048 Riga, Latvia * Correspondence: martins.metals@rtu.lv Abstract: When dealing with the indoor microclimates of cultural and historical heritage cult build- ings, it is important to know the types of these buildings by their spatial volumes and by the types of enclosing structures, and it is also important to understand the moisture transfer processes in these buildings, which would allow one to generate solutions on how to more effectively control the indoor microclimate. Due to the antiquity and specific load of these buildings, the existing standards are not applicable. This study summarizes 275 churches in Latvia, dividing them both according to five spatial volumes and according to the types of the materials used, which makes it possible to create potential air flows for all spatial volumes and to predict condensation risks in the future. Additionally, the results of temperature and humidity measurements in two different churches from one region of Latvia are given and the absolute humidity was calculated, and the data were analyzed depending on the outside air temperature. These measurements have yet to be followed up with the data of a full year. Keywords: church typology; humidity 1. Introduction Understanding the formation of moisture in cultural and historical heritage cult buildings is important in order to be able to properly maintain these cultural and historical heritage objects and to design appropriate ventilation systems for them. Until now, there are no established standards, regulations or studies on humidity parameters in cult buildings in Latvia. There are 226 cult buildings in Latvia that have the status of cultural monuments and another 2378 movable and immovable objects in these and other cult buildings [1]. As a result of an uncontrolled amount of moisture, condensation formed on the enclosing structures and equipment (organ, pulpit, altar), and as a consequence, both enclosing structures and equipment created a favorable environment for the spread of various fungi and other microorganisms [2,3], which often leads to the destruction of these objects. In the study of the microclimate of seven Latvian churches, possible risks of condensa- tion on the inner surfaces of external walls and ceilings were calculated at three different room temperatures and three different indoor relative humidities, where the materials and dimensions of the enclosing structures were taken from the Krimulda (LV) church [1]. Such a calculation does not give a complete picture of the possible formation of condensation risks in churches, because each church could have different materials and dimensions of the surrounding structures. In order to determine the risks of condensation on the internal walls and ceilings of buildings during periods of low temperature, it is necessary to take into account both the outdoor and indoor air temperatures, as well as the types and thicknesses of the enclosing construction materials. In Latvia, one of the three leading denominations—Lutheran—has 337 religious buildings [4–7]. There are several types of materials for the enclosing structures of these cult buildings, and their thicknesses are also different. Houses of worship in Latvia have been built since 1198, and accordingly, the con- struction technologies of these buildings have changed over the course of several hundred Buildings 2022, 12, 1396. https://doi.org/10.3390/buildings12091396 https://www.mdpi.com/journal/buildings