Trombe Parapets

Here's a wonderful example showing that it pays to know your history: The "Trombe Parapets" created for a new project called The Pavilion at Colorado State University in Fort Collins.

Most readers will probably know that a Trombe Wall is a mass wall (usually concrete) placed a few inches behind glass.  Solar energy is stored in the mass, and radiates slowly to temper the room behind.  In The Solar House I reconstruct the history of the Trombe wall, so-named for French engineer Felix Trombe.  (He built the first storage-wall house in Odeillo, France, in 1956, though MIT scientists had tested water-storage walls in 1946.  Douglas Kelbaugh probably coined the term "Trombe Wall" in the 1970s.)

This new application---the Trombe Parapet---is exactly as the name suggests: a small Trombe Wall placed above the roofline.  You can see the Trombe parapets in the image below at the upper left part of the structure.

from http://www.csupavilion.com

A traditional Trombe Wall occupies the South side of a building, and this is an inherent limitation, as views from the interior in that direction may be obscured or limited.  The Trombe Parapet is here placed on the North wall of the building, still facing South, in a location where the occupants are not affected.

And, a traditional Trombe Wall works principally by radiation and natural convection, as the mass wall directly faces the space that it is intended to heat.  In the Trombe Parapet, the mass wall is located in an unoccupied part of the structure, relying on forced air convection to transfer the heat from the storage wall to the spaces in the building.  As the diagram above implies, there is some fan power required because the hot air must be moved downward while cool air is drawn up.  Therefore Trombe Parapets are limited in their efficiency and they are not strictly passive.

Also of note: the more prominent feature in the foreground of the image above is a Katabatic Tower.  This uses evaporative cooling and natural convection to cool the building in summer.  Katabatic means the downward flow of cold air.  This feature (not novel to the CSU Pavilion project) is based on older historical technology.  Similar cooling towers were popular in dwellings in the Middle East in the 18th and 19th centuries.

I learned about this project at the Biennial Conference of the USGBC Wyoming Chapter last fall.  The presenters were: Marc Snyder of 4240 Architecture, Linda Morrison of Ambient Energy, and Dennis Rudko of Cator Ruma & Associates.  As far as I know, these designers created the concept and the name "Trombe Parapets."

Image credit: https://www.usgbc.org/articles/top-10-states-2015-pavilion-laurel-village-csu