Post-holiday returns are creating a logistical challenge for online retailers. When goods purchased online are returned, they make their way back through the supply chain—known as reverse logistics—and into a warehouse. Processing the influx of returned items after the holiday season requires as much as 20% more warehouse space.

"It is a big challenge," Mark Russo of Savills tells GlobeSt.com. "Most returned merchandise ends up in a warehouse. This is where an item gets inspected and sorted, usually by hand. One issue as it relates to warehouse market activity is the seasonality of demand. A great deal of space is needed at peak times of the year, such as following this past holiday season's record retail sales."

Returned goods actually require more warehouse space than a for-sale item, because they are more labor intensive to process and place, according to Russo. "Reverse logistics is space intensive because it involves many touches. Inventory can't be stacked the way that it is in a regular forward logistics warehouse, which means more floor area is needed," he says, estimating there is a need for about 20% more space due to returns after the holiday season.