Concepts of responsive architecture have to date largely involved response to environmental context, in order to mediate ambient environmental factors and modify internal conditions for the comfort of users, with energy efficiency and sustainability as the main impetus. 'Smart' buildings often address little other than technically functional issues, with any ideas of 'design' as a unifying factor being disregarded. At the same time, music and performance art have been in the vanguard of creating digital interaction that intimately involves the user in aesthetic outcomes, in the creation of what Umberto Eco describes as an 'Open Work'. Environments made responsive through embedment of computational technologies can similarly extend usability and user-centred design towards universality, through careful consideration of the relationship between person, context and activity, and of the continuous and ultimately transactional nature of human occupation of built environment. Truly 'smart' environments will learn from and through usage, and can be conceived and designed so as to maximise environmental 'fit' for a wider variety of users, including people described as being 'neurodiverse'. Where user response becomes a significant component in managing a smart environment, the transactional relationship between user and environment is made explicit, and can ultimately be used to drive interaction that favours ease-of-use and personalisation. Inclusion of affective computing in human interaction with built environment offers significant potential for extending the boundaries of Universal Design to include people with autism, people with intellectual disability, and users with acquired cognitive impairment, including that arising from dementia. The same users frequently have issues with sensory-perceptual sensitivity and processing. The resulting mismatch between their individual needs and abilities, and the environments they typically occupy, can give rise to states of chronic and acute anxiety. Analysis of the characteristics of such users gives rise to various 'personas', whose functional and psychosocial needs may be best met by responsive environments which take consideration of affective state, that is, of mood and emotion. Human-computer interaction which marries responsive architecture and affective computing offers a new paradigm for smart environments, which are intrinsically user-centred as a consequence. The technical complexity of designing such an environment must always be balanced by the absolute necessity of utilising Universal Design principles to reduce the underlying technological complexity to a usable interface. This paper is a preliminary exploration of the principles underlying the design of one such responsive environment: an interactive sensory room for children with autism spectrum disorders, (ASDs), which aims to promote relaxation and thus reduce anxiety.