The current ideas on old windows and repair is the glass is not where the energy is lost. It's air leakage around the windows. Approx 85% of energy is lost through air leakage. This issue is being addressed in the restoration. This true in pretty much any older home or buildings. Many old yet solid wood windows are replaced every year with new products.The only "advantage" of these products is the glass and less maintanence. They have a much shorter expected life than an old growth wood window. These appear to be Mahogany