Half of the existing office space across 66 markets around the globe will require some $1 trillion in investment to remain viable, says JLL.

The advisory firm has published the figure in a new report called Opportunity through obsolescence, in which it says between 3.5 billion square feet and 4.6 billion square feet of office area needs upgrading over the medium term.

JLL calculates that 44 percent of projected obsolescence is likely to be in the United States, given higher levels of structural vacancy, along with an additional 34 percent in Europe. Both regions have high numbers of older buildings. According to the report, there is no one measurement to calculate near-term stranding risk, but building age tends to correlate best with the ability to meet tenant, investor and sustainability requirements. This is because older buildings require far more work and capex than some newer properties, which are more likely to have private outdoor spaces, better-managed embodie