Usefulness as a key parameter in the evaluation of accessibility and usability issues in architecture and the built environments:a concept for the understanding of the twin concepts in the Danish building code.

In the Danish building code, the twin concept of accessibility and usability has an open interpretation on a comprehensive level of thinking, whereas the notions generate specific physical requirements on a detailed level when it comes to architecture and built environments. This study has been executed as a case study among 34 experienced professionals, active in the implementation of the twin concept in the built environments in order to facilitate for people with a cognitive or functional impairment. The research material has been assembled by the use of mini-questionnaires that have been synthesized with the informants’ recommendations of exemplary models of appropriately accessible and usable architecture and built environments. The aim of the present study is to position the twin concept of accessibility and usability with regard to their implementation in various types of architecture and the built environments. The informants’ definition of accessibility and usability, paired with their recommended models, suggest that the former refers to computable facts, while the latter encompasses perceivable consequences of the built space that requires further ad hoc solutions in order to promote a universal user-friendliness. Seen as opposing forces, the informants use accessibility and usability in order to define the perceived degree of usefulness of the particular architecture or built environments. Based on the informants’ understanding of the twin concept, this study proposes that accessibility and usability are constituents of the building’s performative capacity in relation to a large and varied group of users. In this paper, this capacity has been termed usefulness. It refers to the fit between the individual user and architecture and the built environments, i.e. the perceived level of independent usages of the built space. Usefulness supplies a theorem for an improved understanding of accessibility and usability in relation to architecture and the built environments. It can be ranged under the roof of the Vitruvian credo of a threefold combination of an aesthetical appearance (venustas), a sustainable structure (firmistas), and adjustments that equip this space with commodity for the user groups (utilitas). This study contributes to the positioning of the twin concept of accessibility and usability in the Danish building legislation. The theorem defines accessibility as a physical constituent of architecture and built environments, while usability refers to both physical and other measures that have been deemed necessary to realize in order to create a usable built space. Ahigh level of accessibility, but a low degree of usability, indicates a high fit between user demands and the programming of the built space. There is a high level of usefulness in an appropriate architectural design