Some estimates put the global homeless rate at 150 million people, but the real figure is difficult to measure - nations around the world define homelessness differently.

Being 'homeless' is more than just sleeping on the streets. The concept of home has social, emotional and security dimensions that are intrinsic to its definition. A sheltered person can still be homeless.

A home, then, provides intangible support, including mental health benefits.

Mental health was added to the United Nations Sustainable Development Goals in 2015. The World Health Organization estimates that 450 million people suffer from mental health disorders, and this number is rising.

Depression is one of the leading causes of disability. Suicide is the fourth leading cause of death among 15- to 29-year-olds. People with severe mental health conditions die prematurely due to preventable physical conditions.

Access to warm, dry, secure, long-term housing is key to mental health. Architecture, views of greenery, security, privacy and affordability all have been shown to have mental health benefits.

Good design can come from traditional knowledge and practices just as well as from 'starchitects' in global centres. The challenge for the world is implementing locally appropriate ideas in our already crowded urban spaces.

The flow-on benefits for society at large are more than just a few prize-winning grand designs. If a person is 'homed', they have a longer-term chance of mental and physical health.