A luxurious estate in Boulder’s Knollwood neighborhood is on the market for $7.5 million. The home sits on a 0.45-acre lot at 2135 Knollwood Drive and faces south so that its floor-to-ceiling windows can flood the main rooms with natural sunlight and take in Boulder Canyon and Flatirons, which are visible from nearly every window of the 5,075-square-foot home. “It’s on the western edge of Boulder right above downtown,” said Tim Goodacre, owner of Goodacre & Company.