• Apr. 12, 2007 - Louisiana thermal mass architecture for wet/hot climate
http://www.leeric.lsu.edu/bgbb/7/ecep/drafting/a/app-a.htm
5. COOLING TECHNIQUES
The proto-type house brought from France to Louisiana was designed more appropriately for longer winter seasons. In adapting that structure to Louisiana the main emphasis was on staying comfortable through the long hot-humid summer season.
5.1 Shading
Shading was the most important and cost effective technique to prevent heat gain then as it is today. It is obvious that the French picked up on this soon after arriving in Louisiana. The lean-to roof, off the major steep hip roof, all around the house worked well to keep the mass walls in shade and protect them from the rain. Solid shutters were used to keep the direct sun from penetrating the structure. These gave way to adjustable louvered shutters that allowed light and ventilation without allowing the direct sun to enter. And trees were used not only to protect the structure from the low angles of the sun in ;the early and late hours of the day, but to reduce the temperature of the area surrounding the house. People dressed light and wore a hat when in the sun.
5.2 Ventilation
The elongated structure with rooms only one deep and openings across from each other provided beneficial ventilation. Sometimes an alley of trees were located in front of the house to provide a shaded channel where a venturi effect added to the velocity and lower temperature of the incoming air. Ceilings were higher which allowed the heat to rise above the people in the house, and transoms allowed this heat to be vented to the outside. The roof was designed so that heat rising up to it could move through the shingles/shakes to be replaced by cooler air. Because the structure was raised off the ground, air could move completely around the structure for added heat removal. The housed was opened at night to help dissipate heat collected during the day, and closed at daylight to retain the cool air as long as possible. A hinged board(s) hanging from the ceiling (punkah) was rocked to provide added air movement at times, and hand fans were popular and useful.
5.3 Radiation
The unusual use of mass in a hot-humid climate seems to be very beneficial if kept out of the sun, well ventilated, and thermally grounded. It provides a cool sink that the human body responds a comfortably to through radiation. The raised basement is built of thick masonry walls that step out as they go below grade, as the foundation, thermally grounding the mass to the earth. The steady state ground temperature for South Louisiana is 68°F. The walls of the second floor (main floor) are brick or mud adding even more mass. Taking heat away from the body by radiation is more comfortable than blowing cold air on individuals.
6. HEATING TECHNIQUE
Louisiana winters are not very long, but it does get cold. The coldest times are when fronts come in from the northwest. With the frontal passage there are clear skies and drier northerly winds.
Fireplaces were normally on interior walls of houses separating two rooms, each with an opening to the fireplace. Infiltration must have been a problem with so many doors and windows, and the fireplaces would have encouraged even more infiltration. There were tools/utensils that allowed you to take hot coals from the fire for other uses, i.e. warming the bed before going to sleep.
Throw rugs were used on wood floors, and people dressed warmer. The sun, being lower in the sky at this time, heats the mass from the outside plus can let light and heat in through the doors and windows.
7. CONCLUSION
Within the first century that Louisiana was being colonized, the architecture of rural French origin was adapted to the very different hot-humid climate of Louisiana by experimentation with materials, construction techniques, building use, and form variations. The Louisiana Raised Cottage is the result of that adaptation. It is a well shaped, well ventilated mass structure that naturally stays within the comfort zone the majority of the year.
Mass, that normally is not a recommendation for use in hot-humid climates, can be used effectively with control of its temperature. |
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