NEW HAVEN, Connecticut — Progress is underway in New Haven on the second affordable housing project in the nation to employ wood in place of steel and concrete. The 69-unit, two-building complex on Dixwell Avenue in New Haven uses mass timber, a wood product and technology that reduces the amount of CO2 emissions used during construction. …City leaders say the production of construction materials account for 10% of the global energy-related carbon pollution contributing to climate change. Unlike steel and concrete, which are commonly used and non-renewable building materials, mass timber employs wood, a renewable resource, and stores carbon in the building structure. …Using the mass-timber style costs slightly more than typical construction, but has more benefits in the long run, project architect Alan Organschi, of Gray Organschi Architecture, said.