Guntersville Dam and powerhouse. Generator hall. Roof is supported by trusses with arched bottom chords, concealed by ceiling made up of asbestos boards on steel furring. Ceiling also serves as insulation and plenum chamber and permits recessing of highbay reflectors which are louvered at bottom to eliminate glare. These reflectors furnish the main working light and throw the generators upon which they are concentrated into strong relief; general illumination of the space comes from indirect reflectors concealed behind the crane relief and turned towards the ceiling. Floor is ceramic tile; wall, glazed structural tile up to ceiling, but of lighter color above crane rail