Sustainable refurbishment is when a building or space is updated to make it more energy efficient and environmentally friendly. This can happen if the building uses too much electricity, if it produces too much waste or pollution, or if it's made from materials that are bad for the environment. When refurbishing a place, engineers look for ways to reduce the amount of energy the building uses, like installing more efficient windows, insulation, or air conditioning systems, and they look for ways to use materials that come from sources that don't damage the environment, like recycled materials. All of these changes help make the building better for the environment and save money on energy bills in the long run.