Windows have a U or R value like insulation, so you can use that to compare. We are currently building a house and the triple glazed windows we chose have a U

Windows have a U or R value like insulation, so you can use that to compare. We are currently building a house and the triple glazed windows we chose have a U value of 0.9. The same manufacturer also makes double glazed windows which have a U value of 1.3.