"Baixa Pombalina", the downtown and historic district of Lisbon is one of the most important pieces of urbanism and architecture ever built in Portugal, and is at present time a UNESCO World Heritage nominate. Those Buildings were built after the great earthquake of 1755, for housing, commercial, and services' functions. And they constitute a rational and functional approach for health and comfort to their residents, translating the state-of-the-art of architecture at the time, through the use of lighting and natural ventilation. In this research study, buildings of "Baixa" are observed as a scenario where residents of 21st Century live in spatial and built structures of 18th Century. This paper is about environmental controls of windows within current thermal and lighting performance of "Baixa Pombalina" Buildings. It analyses the habits of its occupants in controlling and regulating windows in "Baixa" buildings at present time. A questionnaire was developed to study bioclimatic performance of offices, and residences selected in "Baixa". And field work involved a survey where workers of fifteen offices and residents of five houses have participated. Results demonstrate that in buildings of Baixa, windows are used less interactively during winter season and more interactively during summer season. Results indicate that in the Lisbon climate, it is mainly during the summer season that controls have a major role in thermal performance of Baixa's buildings. This Paper aims to show that Regulations shall rate adequately heritage buildings by including in greater consideration, bioclimatic strategies such as natural ventilation, and adaptive actions such as opening windows, as environmental control. (C) 2014 Elsevier Ltd. All rights reserved.