I've been thinking quite a bit recently about intersections between issues of Historic Preservation and issues of Sustainability. Of course this has been on my mind since the demolition of the George Löf house in 2013. More recently, I taught a course (called Historic Preservation & Sustainability) where we looked at the potential for existing buildings to contribute to sustainability goals, and the challenges inherent in preserving/improving buildings from the Thermostat Age.
In the history of the solar house, there are a couple of fundamental issues with regard to preservation. First is Stewart Brand's concept of shearing layers. Brand's idea, which he discussed in the seminal How Buildings Learn, was that a building's different "layers" have different lifespans and therefore will be changed over time.
Many of the seminal experimental solar houses were based upon mechanical systems (Services) which were experimental---no surprise. Here's a great example of how shearing layers works in the history of the solar house: At Colorado State University (CSU), Crowther and Löf built a series of houses in the mid-1970s. All had various active solar heating systems (panels or tubes) on their roofs. Today, one of the houses exists, but its solar heating equipment has been removed. The building still exists, but its integrity has been lost.
I'm given to understand that MIT Solar House IV also still exists in a similar state, without its original equipment.