Is anyone familiar with the field finish coating on CertainTeed fiber cement siding fading and chalking prematurely?  There is a house I worked on where after about three years exposure to sun the paint (a medium dark green) faded and developed a brownish-yellowish chalk like dust on the surface.  It was worse on surfaces with more direct exposure to the sun, however, it was occurring wherever there was exposure to the sun.   All of the manufacturers directions were followed in applying the paint, which was a 15 year, 100% premium acrylic latex paint.  After dealing extensively with the paint manufacturer’s representatives and sending a sample for testing, the conclusion I received from the paint manufacturer was that the problem was due to the topcoat being applied too thin.  The manufacturer said that they had no problems or other complaints with the paint batch I had used.   In my quest for answers, one person stated that it might be that the machine prefinish coat may not have sealed in the high PH in the fiber cement and that this was bleeding through and causing the brownish, yellowish surface.    Has anyone else had experience with the field finish coat prematurely fading from exposure to the sun and what can be done to prevent it in the future?  Would two topcoats help the problem?