What can you use to insulate room from the inside?

To insulate a room from the inside, you can use materials such as foam board, fiberglass batts, or spray foam insulation, which are effective for reducing heat transfer. Additionally, installing insulated curtains or window film can help retain warmth and block drafts. For walls, consider adding a layer of drywall with soundproofing properties for extra insulation. Sealing gaps and cracks with caulk or weather stripping also enhances overall energy efficiency.