Making old homes more energy efficient

The National Trust for Historic Preservation has launched a Weatherization Guide for Older and Historic Buildings. The site includes some interesting advocacy for keeping historic windows in place:

Going green is about more than just energy performance. To determine real environmental impacts, one must take into account the embodied energy of the new and existing windows, the environmental impacts of manufacturing new products, and the expected lifecycle of the product. Embodied energy includes the energy required to extract the raw materials, transport them, make them into a new product, ship the product, and install it. Existing historic windows have all of this energy embodied in them. Tearing out historic windows for replacement units not only wastes embodied energy, it requires additional energy to remove and dispose them. This is on top of the energy required to create and install the new windows.