Radiant thermal barrier

A thermal barrier comprising a radiant heat barrier and an extended length of board deliverable unassembled to a building site, said extended length of board formed for on-site assembly into a channel having a lid covering an open side of said channel to form an enclosure for enclosing said radiant heat barrier, said assembled thermal barrier for insertion as a barrier to thermal radiation into a space between two joists or studs of a floor, wall, roof, or ceiling of said building for completely covering said space while also at least halfway covering protruding edges of said joists or studs, said extended length of board having a plurality of fold lines spaced along said extended length for folding said extended length of board into said channel for said insertion into said space between said joists or studs with edges of said channel lying on said protruding edges for attachment thereto, said extended length of board having a fold line for folding into said lid for covering said open side of said channel to form said enclosure for enclosing said radiant heat barrier placed inside said channel, said radiant heat barrier comprising a reflective surface on an inside face for facing said floor, wall, roof, or ceiling from within said enclosure, said enclosure for providing protection from accumulation of dust on said reflective surface on said inside face of said radiant heat barrier contained in said enclosure, said thermal barrier further comprising a reflective surface on an outside face of said enclosure for facing said floor, wall, roof, or ceiling from outside said enclosure.