Construction has started on an unusual downtown Milwaukee apartment tower. The $80 million project, known as Ascent, is being developed at 700 E. Kilbourn Ave. by New Land Enterprises LLP and Wiechmann Enterprises. Foundation work has started, New Land announced Monday. The building is scheduled for completion in summer of 2022. The 25-story, 259-unit high-rise is being constructed with a technique known as mass timber or cross-laminated timber. …Apartments, offices and other buildings made from timber provide a lower carbon footprint than conventional construction. They also can create a more attractive atmosphere, featuring exposed wood interiors. At 284 feet, Ascent is to be the tallest mass timber structure in the world, according to New Land. The 280-foot-tall Mjøstårnet tower opened in Norway in 2019 and is the world’s tallest such building. But a mass timber high-rise in the works for Sydney, Australia, is planned at 590 feet…