International standards state the thermal comfort requirements that office spaces must comply with. These are based on a model developed by Prof. Paul Ole Fanger of the Centre for Indoor Environment and Energy, Denmark. Today, forty-year Office Buildings research shows an evolution in these experiences. The work presented here is to develop a tool to evaluate the thermal comfort of working environments of office buildings. A methodology is devised on the basis of on-site measurements and questionnaire responses. For measurements, a mobile unit equipped with sensors is used, whereas the questionnaire obtains user responses on thermal quality of the work space. The thermal conditions of thirty office buildings presenting different acclimatization systems have been surveyed. The correlation between objective and subjective data allows developing a formula that shows the thermal comfort level for a given environment as a function of local aspects. For the surveyed buildings, the resulting comfortable temperature was 23.3℃, and the minimum percentage of user individuals experiencing discomfort with such temperature was 7%.

The quantitative definition of thermal comfort for any given space can be stated by applying the PPD Index (Predicted Percentage of Dissatisfied) as proposed by the standard [1] . This index is built upon a mathematical model developed by Fanger using data from experiences made with humans in a controlled climatic chamber. The individual responses render a thermal sensation vote which is then related with the corresponding operative thermal measurement readings [2] . The model responds on a small sample of people sharing a pre-defined thermal environment. This means that, while the operative temperature is varied in the 66 to 90˚F (18.9˚C to 32.2˚C) range, the remaining physical parameters affecting the thermal comfort (e.g., air speed and humidity) and the person’s physical and physiological factors (clothing insulation and activity levels) are kept constant.

Research results from [3] and [4] have shown that the user’s behavior indicates that even in spaces having constant thermal conditions, they are capable of experiencing adaptation processes which allow them to accept thermal conditions imposed by the building manager controlling the HVAC system. Other authors [5] [6] state that personal factors, such as body build-up, gender and food intake and close vicinity parameters, such as the external climate, affect the thermal perceptions of persons. According to these authors, the users express a critical attitude of the thermal environment conditions that is then translated into a continuous adaptation process [7] – [9] .

Various field works have shown that there is an interrelationship between climatic and non climatic factors and their influence on thermal comfort in actual work spaces. Several authors [10] – [14] state that the use of standards, such as [1] , based on Fanger’s model, evinces deviations stemming from causes inherent to the very method used to attain it. Besides, these approaches become constrained when trying to have a holistic vision on comfort, and they are certainly useful only when the internal conditions are kept constant and within pre-established ranges. They show, moreover, that the adaptation capability of users to the various thermal environments is not considered in the experiments made in climatic chambers.

The method presented in this paper is based on making measurements and having the space users fill questionnaires simultaneously to the measuring sessions carried out as a field work in 30 building offices in Germany [3] [4] . Measurements are made with a mobile unit equipped with high-precision sensors, and the questionnaire contains questions on thermal aspects of their work space. Through the user vote, these results are translated into a value scale. Results evaluations show strong correlations among the mean vote on thermal sensation, the mean vote on thermal preference and the operative measured temperature readings.

As a contribution, the work defines criteria on thermal neutrality (thermal satisfaction). Besides, a model is developed to predict the variable thermal comfort in office buildings and a methodology is devised to elaborate computational tools for professionals working in this disciplinary area. These tools should help address the monitoring and evaluation of thermal parameters of real work space that may lead to establish indicators on the environmental quality of buildings.