Fans of the renovation show “This Old House” will appreciate this Upper West Side townhouse at 21 West 75th Street. Bob Vila, the host of the show for 10 years, owned the home with his son, Chris. Built in 1909 by John C. Umberfield and designed by architect George Walgrove, the historic townhouse inspired many episodes of the show. And in the show’s spirit, it was more recently renovated and restored before being divided into five condos. This condo, asking $2.5 million, occupies the full third floor of the property.