Radiant barriers are an integral part of Hawaii’s energy code. The question came up about radiant barriers discoloring “like old silverware” over time, and of course, dust collection is an issue. Does the association measure performance drop–perhaps the same way that the CRRC measures aged reflectance over 3 years?
Thanks for your good questions. Aluminum foil does oxidize very quickly in the presence of air. By the time a reflective insulation or radiant barrier is installed, the oxidation is usually complete. Unless there are unusual air quality issues facing the aluminum surface, it will not change appearance over time — aluminum foil isn’t like silver. I’ve had radiant barrier installed in my home for over 25 years and it is still as shinny as when new.
As to the dust issue, if the radiant barrier is installed according to RIMA’s guidelines — attached to the underside of the roof rafters, dust accumulation should not be an issue. Where the radiant barrier has been installed laying on the floor of the attic, dust can represent an issue of reduced reflectivity which would affect the thermal performance. The amount of time that would take is dependent upon a variety of variables. Estimating the amount of loss of performance based upon dust accumulation is very hard to do. What kind of dust would one use? How would it build up on the surface — evenly or erratic? Too many complicating issues to make an evaluation that would be particularly valuable. Certainly, a visual inspection could be used to determine when the radiant barrier needed to be cleaned off or turned over.