Home Depot offers the Enerflex 1.33x4-Foot Radiant Barrier 10-Pack, model no. 115360, for $8.50. Choose in-store pickup to avoid the $5.99 shipping fee. That's the lowest price we could find by $15. It's designed for insulating attics along the underside of the roof and purports to block up to 96% of radiant energy, keeping attics warmer in winter and up to 30° cooler in warm weather. Deal ends March 24.