The outer half of the radiant barrier was installed today in the attic - all that shiny aluminized housewrap. The early returns suggest that it works: air temperature got up to 83 degrees today, shingle temperature reached 135 degrees, but the attic temperature didn't get above 85. The attic is still completely open to the rest of the house, until the walls are built, so it's absorbing all the heat load from the house as well as solar.The rest of the barrier goes right under the drywall. I'm going to leave the lower half (cripple walls) unfaced, to avoid more interference with wireless signals. So far both cellular and wlan signals seem to be unaffected.