3. Gap Analysis of the Long-Term Discomfort Indices and a Harmonized Calculation Framework

Long-term discomfort indices depend on a number of boundary parameters that are currently not univocally defined in standards, although they have a large influence on the results. Specifically, EN 15251 and ASHRAE 55 do not clarify some gaps and provide a wide margin of discretion to the analyst when calculating them. In order to assess gaps and needs for using long-term discomfort indices, a selection of such indices has been tested, during a summer period, by means of a sensitivity analysis. It was found that the sensitively to given gaps is higher for those building variants characterized by lower discomfort levels. In order to make the long-term discomfort indices reliable tools (i) for establishing requirements about the indoor thermal environment of buildings, (ii) for driving the comfort-optimization of buildings and (iii) for assessing their comfort performance during the operational phase, the identified gaps shall be fixed, and it is desirable that they are framed in a common and accepted standard framework. Finally, a calculation framework is proposed, and a new method for calculating the extension of the calculation period (seasons) is also presented.