Pavilions — large-roofed, often open-air and tent-like structures — get their name from the Latin word papilio for "butterfly." It is the shape of the butterfly's wings, drawn partway down, that gives us the normal image of the sheltering pavilion.

But we typically think of the butterfly with wings extended and up, and it is this image that gives us the term butterfly roof — a roof with two surfaces that rise from a low valley at their center to higher eaves at their edge. Architect Constance Treadwell's house in Hawaii is a true pavilion, because it is both an open-air, tent-like structure and a low-at-the-middle, wings-raised butterfly roof (complete with butterfly chairs!).

The two surfaces of the corrugated metal roof slope in toward the center at a pitch of 1.5 in 12 (7 degrees), rising gently toward the edge, a shape that Treadwell describes as inspired by the image of "a delicate, winged insect alighting on the land."

Another inspiration for the roof shape comes from the historic necessity in the arid climate of western Hawaii of using the roof surface to collect water. The butterfly roof channels the rainfall to one point and enables the owner to gather and use the 6 inches (15 centimeters) per year that fall on the broad roof of this one-story 1,500-square-foot (140-square-meter) house.

The house consists of two parts, each with its own roof — a bedroom/ bath wing and a commons, with kitchen and large main room and covered outdoor room. In a region where shelter means a protected, shady place with good ventilation, this roof strategy provides a high, open, and airy quality.

The roof over the main room, springing from a height of about 9 feet (2.7 meters) at the center and rising on its south edge to 11 feet (3.4 meters), extends directly out from the room, whose western wall is essentially designed to fold back and disappear over a deck. This creates one large living space, which is half inside and half outside, the whole of it protected by the high floating roof above.

Storm shutters are used both to protect the screened openings on the south side in bad weather and to form a kind of eave line, masking the view of the neighbors to the south and creating the look of a low sheltering edge in this otherwise open, high-ceilinged space.

In a climate with little rain and essentially no winter, this is a sheltering roof that turns roof conventions inside out, striking a wonderful balance between open and contained.

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Patterns of Home

Part of the ArchitectureWeek Patterns series. Text and images excerpted with permission from Patterns of Home: The Ten Essentials of Enduring Design by Max Jacobson, Murray Silverstein, and Barbara Winslow, copyright © 2002 The Taunton Press, Inc. The book is available from The Taunton Press and at Amazon.com.