Churches, chapels and other places of worship are a major part of European cultural heritage which modern society has decided should be preserved for future generations. The indoor environment of these buildings crucial to conserving construction elements and movable artefacts. In addition, in the Mediterranean the growing demand for thermal comfort from society has made the use of active environmental conditioning systems more common in spaces of worship. However, most of these techniques cannot simultaneously satisfy the needs of heritage preservation, human comfort and energy efficiency. In addition, energy consumption in such spaces tends to be high due to their large size and high thermal inertia. In some Mediterranean countries including Spain the thermal envelopes of these buildings are not contemplated in current environmental conditioning regulations. However, all thermal installations must ensure conditions of wellbeing, safety and energy efficiency. Studies such as European Project Friendly-Heating highlight the problems caused by installing heating in old churches. The case of the Spanish churches in Mediterranean climate is very different from that of the churches in northern Europe. Due to the temperate climate, heating demand is much lower in winter, while in spring and summer the demand for cooling and dehumidification is greater due to the high temperatures and outdoor humidity. This article describes research on environmental conditioning techniques, both passive and active, in spaces of worship in temperate climates. The main aim is to describe different environmental techniques to improve the thermal comfort conditions of the faithful while preserving the cultural heritage of these buildings. Different strategies and regimes were tested using monitoring and simulation. The software used was Design Builder version 3.4.0.041, EnergyPlus 8.1 and the simulation model was validated through measurement. Currently, the church does not present comfort conditions and preservation of the artworks throughout the year. In addition, the exclusive use of passive environmental techniques does not completely eliminate the risks. Finally, the detailed knowledge about the hygrothermal response of the church with a validated simulation model after installing HVAC could lead to energy savings and the improvement of conservation and thermal comfort. (C) 2016 Elsevier B.V. All rights reserved.