Methods of making thermal insulation products are provided, one method including the steps of sealing a support material (e.g., a nanoporous core such as fumed silica, an aerogel powder, etc.) and at least one vapor (e.g., steam) within an interior portion of a substantially gas-impermeable envelope (e.g., a metallic and/or polymeric film), and then condensing at least a portion of the vapor after the sealing step to reduce the pressure within the gas-impermeable envelope from a first pressure before the condensing to a lower second pressure after the condensing. The disclosed methods limit or eliminate the need for mechanism pumping mechanisms to drawing the vacuum within the products, drying of the core before the sealing, and the like.