Deck-applied radiant barriers do not work as well as applying the radiant barrier to the bottom of the roof rafters, the way our Silver Shield™ Multi-layer Radiant Barrier is installed.

  1. Good: Deck-applied Radiant Barriers (1 airspace below the radiant barrier surface)
  2. Better: Draped over the rafters (2 airspaces: 1 airspace above and below the radiant barrier)
  3. Best: Attached to the bottom of the top cord of the roof truss or roof rafters (3 airspaces: one above, one below and one in between the layers of the multi-layer radiant barrier. This application allows for the bottom of the roof rafter to be completely covered with foil.)

In summary, you want as much of the roof deck covered with low-emittance materials (foil). Deck-applied and draped radiant barriers sandwich the foil between the top cord and the roof deck. This area will continue to radiate as if there were no radiant barrier. The total area of roof rafters (compared to the total underside of the roof surface) is as much as 35% – that’s a lot. This means that 35% of the bottom of the roof surface radiates at a high rate (82% to 90%) as opposed to the surface of the foil radiant barrier, which only radiates at 3% to 5%. Covering the roof rafters with a low-emittance radiant barrier improves the overall performance of the radiant barrier application. FI-FOIL® recommends that you use the bottom of the roof rafter application and the premium product for this application – Silver Shield™ Radiant Barrier, a multi-layer radiant barrier. Radiant barriers, like many other products, have different performance levels. However, the performance of these products is not only attributed to the product but to the application, as well. If you are going to do the job, why not insist on the best application and the best product for the application? FI-FOIL® has products for all three applications.