Fire-retardant panels that include: a frame with multiple holes that reduce heat conduction through the panel; or a frame that includes two portions separated by a layer of fire-resistant material (e.g., gypsum, calcium silicate, or gypsum board). Some embodiments include skins (e.g., sheet metal) or insulation (e.g., between skin and fire-resistant material, for instance, within the frame). In particular embodiments, the fire-resistant material is (e.g., midway) between: two skins, two layers of insulation, two portions of the frame, or a combination thereof. The portions of the frame can be: sheet metal, attached (e.g., screwed) to the skin(s) or to each other, or extend around the perimeter. The frame can include: various elongated members, (e.g., parallel) bends, or holes that are: in at least one row, elongated, or slots (e.g., parallel to each other or to the skin).