Quick Summary of Results from FSEC Study on the Effect of Roof Construction on Attic Temperatures: http://www.builditsolar.com/Projects/Cooling/FSECRoofPaperSummary.htm
results:
Typical mid June attic temperatures with various roof constructions
Attic
Temp Roof Material + Ventilation Area
134.9 Black shingles, no radiant barrier, ventilation area 1 in 300
128.1 Black shingles, radiant barrier, ventilation area 1 in 300
116.1 Black shingles, radiant barrier, ventilation arae 1 in 150
115.7 Red tile
102.2 White metal (68% reflectance)
091.5 White tile (72% reflectance)
For this typical day, peak ambient temperature was 92F.
Conclusions:
The radiant barrier alone results in a modest improvement
The radiant barrier plus more ventilation area results in somewhat more improvement
A dark colored tile roof is about as good as radiant barrier plus more ventilation
White tile or white metal roofs result in a marked improvement over all the above.
David's White Roof Experiment: http://www.builditsolar.com/Projects/Cooling/WhiteRoofExperiment/WhiteRoof.htm
results:
House temperatures with regular roof and AC OFF......... 87-92F.
WHITE ROOF (and ac OFF)........ 79-82F.
ATTIC temperatures with regular roof.................... 120 - 140F
WHITE roof ................... 90 - 97F