Complex design challenges exist in designing for a dynamic and ageing world. Designing for older adults is a timely and important issue. Understanding user requirements is vital and the appropriate exchange of this knowledge is crucial in the pursuit of supportive, sustainable buildings and the longevity of built-environment design. Capturing reflections from Built Environment Professionals (BEPs) in the UK, this paper investigates the practitioners' viewpoint on knowledge exchange by specifically focusing on the scenario of designing for the requirements of older people. Thematic analysis of BEP conversations (n=10) and the results from a questionnaire (N=35) are presented. Findings uncover recommendations towards the enhancement of knowledge exchange. They highlight the fundamentals of good communication, the desire for structured knowledge, the value of contextual guidance, the importance of a visual format for BEPs, and the need for forms of guidance to support client motivations. The design process can be enabled by equipping practitioners with information about user requirements. Interestingly, it was also found that BEPs find value in direct user-engagement although further support tools for these engagements with building users was desired. Appropriate exchange of knowledge is essential for effective 'real-world' design impact. These findings, built from the scenario of designing for older adults, also apply to the broader context of all guidance used by Built Environment Professionals.