I’m using 9” 13 ga. girders on a galvanized metal building. The building will be wrapped with OSB, then moisture barrier wrap and fiber cement siding, using radiant barrier. My question is would foil radiant barrier be effective if applied between OSB and galvanized girders/columns as long as I keep the interior open for air gap? My second application choice is to apply radiant barrier on inside of building, which then means all you see once inside is the foil barrier.
There are several options available to you from the RIMA manufacturer members. You could use OSB with foil already laminated to one side, installed with the foil side to the inside of the building. Or you could use a foil/bubble type insulation material draped between the purlins before you install the roof/siding. Or you could install a reflective insulation or radiant barrier on the inside, attached to the face of the purlins/girders. The last suggestion would be a new reflective product that installs on the inside between girders, that has a reflective surface, that would face upwards with a white finish facing the inside of the building.
I don’t know where your building is and wonder what building code requirements you may have. You may have to use a combination of reflective material and mass insulation to achieve code compliance — especially if the building is to be conditioned.