As an energy‐saving building material, transparent wood (TW) is highly attractive because of the advantages of high optical transmittance, excellent mechanical properties, and good thermal insulation. However, the current research is limited to fabricating small‐size samples in the laboratory because thick or large‐size transparent wood is almost impossible to be achieved. A method that can easily and efficiently produce transparent wood with any size and any thickness is desirable for practical applications. Transparent wood made from wood fibers as a substrate allows the cell walls to bind more tightly to the impregnated polymer, resulting in high light transmittance. Compared with wood prepared by using previously reported approaches, the transparent wood prepared by this new method not only retains the same advantages but also has higher preparation efficiency and is suitable for large‐scale production. Under a simulated real environment, the retainability of indoor temperature by a sample house utilizing the transparent wood reveals excellent thermal insulation of the fiber‐based transparent wood owing to its low thermal conductivity, showing significant benefits in saving thermal energy.