(Background) (Methodology) (Building Results) (Model Results) (Conclusion) (References).

Purpose

Before the availability of modern active cooling systems, Mississippians had to rely on their natural surroundings to cool their homes. Some homeowners designed houses which responded to the environment to enhance passive cooling. Although books are available (Ref.4,5,6) which document design techniques for passive cooling in Mississippi's hot/humid climate, they do not provide evidence that the buildings perform as intended. Therefore, the purpose of this case study is to test and document the effectiveness of one passive cooling technique -- the stack effect -- in a historical Mississippi building. Tests will be conducted using easily constructed equipment so that other students can conduct similar studies to test other buildings or their own design ideas in studio projects.

The Past

The focus of this study is Waverley Mansion, an ante-bellum home in West Point, Mississippi designed by Sir Charles Pond in 1850. Pond took on the challenge of passive cooling in Mississippi, a state known for its high humidity level. He incorporated into Waverley multiple passive cooling solutions responsive to the environment. Many of his design solutions were common to historical Mississippi architecture.

Figure 1a: The plan of Waverley Mansion.

In order to promote passive cooling, early residents of Mississippi realized that one way to increase their comfort in the hot/humid climate was to increase air motion. The first house type to respond to Mississippi's climate appeared in 1790 and is known as a dog trot. Dog trots consisted of two south oriented log rooms separated by an open space. When summer winds hit the house, a pressure differential was created which increased air speed between the two log rooms; this, in turn, increased ventilation and occupant comfort. Viewing Waverley Mansion in plan (Fig.1.a) reveals a strong dog trot influence (Fig.1.b).

Figure 1b: A traditional dog trot plan.

Waverley combines several conventional passive techniques to help cool itself: 1) The building is raised off of the ground to promote convective cooling. 2) Porches provided inhabitable outdoor space. 3) Shutters were used to block direct sun light and rain while permitting prevailing breezes to enter the building. 4) High ceilings allowed hot air to rise above living spaces. 5) Openings placed high on the walls let hot air escape, which pulled cooler air inside (thermal buoyancy). Waverley's designer cleverly combined all of these passive cooling techniques and drastically improved on one -- the house's highest ceiling, located in the central atrium space, is 52 feet from the ground (Fig.2).

Figure 2: Section through the 52' atrium at Waverley Mansion.

Sir Charles Pond improved on conventional one story dog trot architecture by increasing the height of Waverley's central space from one story to four stories (Fig.2). Natural thermal buoyancy caused warm air to rise to the cupola at the top of the central atrium space. The cupola was built with sixteen windows (oriented in eight directions) to allow the hot air to escape. Cool air was then pulled into the living spaces on the lower levels from the outside. All of the living spaces were positioned east or west of the atrium. Each living space had operable windows or doors on three sides which increased cross ventilation throughout the house. Transoms were used above the interior doors so that air could flow from room to room even when the doors were shut (Fig.3).

Figure 3: Transoms at Waverley Mansion.

The Present

Given the research of historical passive cooling techniques in Mississippi, Waverley should be able to cool itself without mechanical means. This becomes questionable, however, when the many changes in Waverley over the past 150 years are considered.

• A wall of concrete now connects the house to the ground on the south side (Fig.5).
• The transoms above each of the interior doors have been painted shut.
• Some of the shutters have been lost, leaving those windows without protection from direct sunlight. All of the windows on the south side have shutters.
• One of the exterior doors on the north side no longer opens (Fig. 4).
• Seventeen of Waverley's forty-eight windows are either painted or nailed shut (Fig. 4).

Figure 4: The doors and windows which are no longer operable are shown in red.


Figure 5a: South Elevation at Waverley Mansion. Windows that no longer operate contain an "X".



Figure 5b: West Elevation at Waverley Mansion. Windows that no longer operate contain an "X".

Despite the changes Waverley has undergone, its diversity insures its survival. Waverley Mansion continues to successfully cool itself passively using the four-story atrium to increase indoor air movement via the stack effect.

Comments to author: vitalsigns@
ced.berkeley.edu

All contents copyright (C) 1998. Vital Signs Project. All rights reserved.

Created: 04/08/97
Revised: 09/09/02

http://www-archfp.ced.berkeley.edu/vitalsigns/workup/waverly/waver_bkgd.html