Vietnam battles severe air pollution and substandard infrastructure, leading to Sick Building Syndrome (SBS), even in healthcare facilities. Enhancing Indoor Air Quality (IAQ) in hospital design and renovations is vital for safeguarding vulnerable groups, such as patients, children, and the elderly. However, akin to other developing nations, Vietnam must address specific local challenges before devising any strategies to improve IAQ in these critical settings. In this study, we identify factors influencing the selection of methods to improve Indoor Air Quality (IAQ) in healthcare facilities, considering Vietnam's specific conditions. 16 potential factors have been investigated and categorised into 4 influence groups based on a comprehensive literature review and validated by a survey of 160 architects, engineers, project managers, and hospital staff. We conducted an academic literature review to pinpoint these factors and propose design solutions. Additionally, we surveyed and quantified the effects from the perspective of Vietnamese healthcare experts. Based on our findings, we discussed the impact of these factors and suggested solutions for enhancing IAQ during the design and renovation phases of hospitals. The study's contribution lies in its practical insights for stakeholders seeking to improve IAQ. The outcomes of this study aim to provide a foundation for developing guidelines and standards to assess construction quality in healthcare facilities.