The Courtyard House Plugin is essentially a house within a house. It is a prefabricated modular system designed to bring modern living standards and energy efficiency to buildings that are centuries old, while keeping them fully intact. The ambition of the Plugin is to renew interest in historic neighborhoods not as tourist destinations, but as places for living. The Plugin at Courtyard 72 is part of Dashilar District’s Urban Regeneration Pilot. Located in the center of Beijing, Dashilar is a historic area dotted with traditional Chinese courtyard houses that are partially occupied. The cost of renovating or rebuilding these courtyards often outweigh the financial benefits for the owners. These old structures lack modern insulation, private bathrooms and can be permanently damaged by new interventions. Thus, neglected courtyard structures that have fallen into disrepair are common sights in Dashilar. The Courtyard House Plugin provides an alternative to this problem. The designers developed a new type of prefabricated panel made of a composite that incorporates structure, insulation, wiring, plumbing, windows, doors, interior and exterior finishes into one moulded part. Panels are light, easy to handle, and cheap to ship. They snap and lock together with the use of a single tool – a hex wrench. The entire Plugin structure can be assembled by a few people in one day, and requires no skill or special training. And because they are mass-produced, Plugin panels can be made in high quality, yet remain inexpensive. ‘Plugging in’ is half the cost of renovating an old courtyard house and about a fifth the cost of tearing down and rebuilding a new courtyard. The Courtyard House Plugin also presents an alternative approach to preservation. In China, countless examples of ‘historic preservation’ projects are merely sanitised versions of old buildings that ignore and erase the traces of history. The Plugin extends the life of courtyard houses by upgrading their relevant functions while keeping the original building untouched.