≈0.4–0.7 t depending on product and cullet share; carbonates in the batch add a process component (~20%) that only cullet displaces.
From our guide: Decarbonizing Glass — full context, charts and sources there.
Boilers, kilns, heat exchangers, valves and steam lines lose energy continuously. Inzonex makes patented (UK GB2508992.1) removable modular insulation — snap-fastened covers engineered per temperature tier, not generic off-the-shelf jackets: