Here is a fairly good article on the subjecct.
"Radiant barrier spray-on paint is essentially liquid foil. While not all radiant barrier paints are the same, basically they are made by grinding pure ... read more
John
I would do what Paul said but I would take an additonal step of capping the sprinkler heads where they are easy to get to with a half dozen of 1/2" PVC caps. Then you are increasing the pressure ... read more