Solar Roof Cooling by Evaporation

Abstract

It is generally recognized that as much as 60% of the air conditioning load in a building is generated by solar heat from the roof.

This paper on SOLAR ROOF COOLING BY EVAPORATION is presented in slide form, tracing the history of 'nature's way of cooling' from its inception to the present. Included in the presentation are the current engineering techniques, design of the system, and documented Case Histories showing paybacks of ten to twenty-four months.

Roof cooling by evaporation of a thin film of water sprayed intermittently on the roof can reduce the surface temperature of the roof from as high as 165o to 88o , thus virtually eliminating the penetration of solar heat into the building.

ASHVE, the forerunner of ASHRAE, conducted extensive tests in its laboratory in Washington, D.C. in 1939 to determine the effectiveness of a damp roof as compared to a dry roof where cooling was desired. The results concluded an 87% reduction of heat penetration into the building on which the roof had been dampened. A presentation was made at the 1940 semi-annual meeting of the American Society of Heating and Ventilating Engineers entitled 'Summer Cooling Load as Affected by Heat Gain Through Dry, Sprinkled and Water Covered Roofs.' Solar evaporative roof cooling has today become a proven energy-saving technique that has been thoroughly investigated and installed by numerous major corporations throughout the country.