Radiant barrier reduces the inside temperature by reflecting 95-97% of the radiant heat away from the building and building materials. When those materials are not absorbing heat and re-releasing that radiant heat back into the structure, the cross ventilation will easily bring the inside air within 1 or 2 degrees of ambient outside air temperatures.
If the building materials absorb radiant heat, the inside temperature will exceed the outside by 20-40 degrees. Garages, barns, carports, hangars, sheds, warehouses all benefit from radiant barrier use which, will create and maintain a comfortable interior temperature
Remember, these are not conditioned living spaces so they will be hotter, cooler and wetter than a home or office space. The goal again, is to reduce the continual heat gain and to soften the cold during winter. Good cross ventilation will prevent air stagnation which, promotes humidity and moisture problems.
There are various installation choices however the fastest and easiest is to use Premium Stiff Bubble with speed tabs. Ventilation is critical so remember to never cover the vents creating that magnificent cross breeze. If there is air circulation behind the bubble radiant barrier, the R-value of the application including the spacers and air space will be reduced if not completely negated. Remember, R value equals trapped air and air does not conduct heat so as long as there is the required spacers and spacing between the roof and the radiant barrier, the radiant heat will jump that air space but it will meet the foil layer on the other side and will be reflected back out.
The NEW Premium Stiff Bubble with speed tabs, 3 inch tabs on both sides, makes installation a breeze. The bubble core provides a thermal break as well, separating the cooler air above the insulation from the warm air directly below it.
Whatever your project for a metal structure, the smartest advancement for the smallest initial investment, will be the addition of radiant barrier. A single layer installed closest to the outside will give you a more comfortable and efficient building.
If you plan on breaking that pesky Thermal Bridge, the photo below shows how one customer of ours using spacers for the barrier applications broke the bridge on his metal structure.