Similarly, it’s a common fallacy that (unless you are renovating your house to passive house energy standards) new windows are more energy efficient or durable than historic ones. First, it will take up to 240 years to recoup enough money from energy savings to pay back the cost of installing replacement windows. Second, let’s be real: New windows are not nearly as good looking. Old windows are very hard to replace, but much easier and often cheaper to restore to modern standards. Finally, no other types of

Source: Home renovation: where to start – Curbed