I just happened to stumble across your 12/14/99 note regarding your Galvalume roof, the inexpensive fasteners you used, and your plans to "insulate coat" the roof with material from icc-astec.
First let me say you are right-on in promoting the long life of Galvalume sheet. I've personally been on the oldest Galvalume roofs in the country, located in the heart of the acid-rain belt, and after 25 years they look great. These roofs have many, many years to go without significant maintenance. Our test panels are now over 30 years old and continue to show outstanding performance. The Galvalume technology has been licensed to over 40 steel producers in over 25 countries.
Second, however, I disagree with inexpensive fasteners. I have been on beautiful Galvalume roofs with rusty fasteners and it makes you cringe. A beautiful roof turned ugly for the sake of cheap fasteners. When you're talking 25-30 or more years, anything galvanized will be rusted (unless you live in the desert). The ZAC fasteners are excellent, as are 300 series stainless steel. But galvanized, electroplated, painted, etc., will just not hold up. They will be red-rusted, and could cause rust run-down stain on the panels that is even more visible.
Third, putting any type of coating on a Galvalume roof is not a good idea. You are taking a roof with a very long maintenance-free life and turning it into a roof that will require regular maintenance and re-coating. ICC-ASTEC recommends re-coating every 10 years. Bare Galvalume sheet, and our new Galvalume Plus, are very reflective materials. We have obtained the EPA Energy Star rating for roof panels made from Galvalume sheet. We were required to test new panels and roofs in service for 3 years. Galvalume sheet is very reflective and loses its refelctivity very slowly, meeting the EPA requirements. Galvalume sheet tends to shed the dirt, i.e., the dirt and dust tend to wash off in rainstorms. That may not be true of some of the specialized coatings -- they can age rapidly and/or hold the dirt and thereby lose their reflectivity.
In summary, we don't recommend taking one of the most trouble-free, maintenance-free, long-lived materials available and turning it into something that will require regular maintenance.
I suspect that you've already got your roof coated by now. Let us know how it turned out and how it holds up.
Keep up the good work!
Bethlehem Steel Corporation