Located in a stunning building east of the National Portrait Gallery and the Capital One Arena, the National Building Museum has an amazing amount of open space. A vast chamber of beautiful columns, gilding and skylights, it hosts nine exhibitions and some extra on the history of the building as the original Civil War Pensioner building and a small bakery.
I enjoyed the exhibit on the planned communities surrounding US development of nuclear weapons, the modular interiors exhibit (future of US housing) and a general exhibit on American housing.
I had hoped for a larger exhibit on the history of architecture and engineering in the US, including the migration and evolution of building styles and design over the years. What they had was informative but didn't feel comprehensive for America's history of structure and design -- at least, not in my mind.
Others might be more than impressed, so don't let this stop you from visiting. Overall, the building, alone, is worth visiting and walking through, which is free.