Attics can be extremely hot in summer and cold in winter. Having plenty of insulation helps. In homes with vented attics, insulation usually goes in any wall or ceiling of conditioned rooms adjacent to the attic. Take care not to lose vent area by allowing insulation to cover any vents. In unvented attics, the insulation follows the new thermal boundary, typically at the roofline.
If turning your attic unvented means that your heating and cooling equipment will now be inside the conditioned space, consider investing in insulation beyond the levels recommended for your climate zone. The investment will probably pay for itself in short order.
Will a Radiant Barrier Help?
A radiant barrier is a shiny surface that reflects or reduces the emission of radiant energy—usually heat from the sun. Radiant barriers are sometimes included as a component of a cool-roof system to reduce summer heat gain. The barrier can be a reflective foil (most common), reflective metal roof shingles, or reflective laminated roof sheathing.
In cold climates, radiant barriers are generally not effective or economical. In hot climates, if your roof is not already well insulated, a radiant barrier can save on cooling energy and improve your summer comfort. But radiant barriers can be tricky, so it’s probably simpler and more effective to insulate your attic properly than to install a radiant barrier.
However, if you’re planning to reroof, and if you live in a hot climate, look into ENERGY STAR-rated roofing products. These have been developed to reduce cooling demands by reflecting solar heat.