Nan Madol
High thermal mass architecture does have historic precedent in Micronesia. The ruins of Nan Madol are good examples of this. Built on the southeastern end of Pohnpei, they were constructed over a period of 1000 years, from 500 AD to the mid 1500’s.





Nan Madol, which translates to mean "Places in Between" to mark the numerous islets that are cross-cut by the many waterways to form the site, is located off the southeast coast of Madolenihmw municipality on Pohnpei Island, Micronesia. The site was constructed on a reef area referred to as Sounahleng, or "Reef of Heaven." Nan Madol consists of 92 man-made islets, covering an area of approximately 200 acres, with each islet serving as a site for one or more specialized activities consistent with Nan Madol’s role as an island-wide political and religious center.

The megalithic architecture that characterizes the site consists of long, naturally prismatic log-like basalt stones which were often built up over foundations of large basalt boulders to form high-walled rectangular enclosures. These prisms were brought in from quarries located at various places around the island with coral rubble being used as fill for the islets’ floors. This type of architecture occurs only sporadically on the main island which suggests that the people who used these structures were of very high status. (Nan Madol brochure, by the Pohnpei Tourist Commission, U.S. National Park Service and the Australian Government.)

It is not known whether the original builders considered the advantage of a high thermal mass assembly cooled through conductivity and evaporation via the surrounding ocean water, when they chose this method of construction. They were probably more concerned with durability and defense.

Today there is an understanding of the concept of cooling through the use of shaded thermal mass. Some of the people I met considered concrete construction to be one of the best methods of cooling available though I rarely saw this procedure done well. Usually the use of concrete was done with minimum roof overhang, allowing direct solar gains into the living space as well as heating the building in general. I found no direct tie between Nan Madol as an archetype and the concrete houses that are being built today on Pohnpei. Similar architectural ruins can be found on Kosrae, again, however, no links were visible between the pre-historic architecture and the masonry buildings at present on the island.