Quantifying occupant comfort: are combined indices of the indoor environment practicable?

What are the various ways in which evaluation of the several aspects of the indoor environment might combine to form an occupant's overall assessment of that environment? Data from an environmental survey of 26 offices in Europe (the Smart Controls and Thermal Comfort, or SCATs, project) are used. These show that dissatisfaction with one or more aspects of the indoor environment does not necessarily produce dissatisfaction with the environment overall. Conversely, satisfaction with one or more environmental aspect does not necessarily produce satisfaction with the total environment. Building occupants balance the good features against the bad to reach their overall assessment. Not all aspects are equally important in this subjective averaging process. Satisfaction with warmth and air quality is more important than satisfaction with the level of lighting or humidity. The relative importance of the various aspects differed from country to country, making it impossible to develop an internationally valid index to rate office environments by means of a single number. The best linear index constructed from the data failed to rank the indoor environments of the buildings in the correct order, as defined by the occupants' overall assessments. It is therefore wise to assess each of the several aspects separately rather than rely only on a combined index.