Wood windows are an integral part of the innate energy efficiency of historical buildings. If we have learned anything from history it is that sometimes with all our modern advancements we do ourselves more harm than good.
Advancements in technology do not always produce better results, and construction technology isn’t exempt from that. Built in a time of readily available building materials and energy sources, modern building designs typically make poor use of both. Historical buildings were built when neither was in abundant supply and early designers made the most of building materials and design options to construct buildings with a powerful combination of harnessed natural resources and innovative design that worked together to maximize energy efficiency.
Everything from exterior paint colors, to locations of balconies, to numbers and placement of windows, to physical placement of buildings on lots was carefully considered to maximize heating, lighting, and ventilation in traditional construction.
The results are astounding and studies have shown that properly restored and maintained 18th & 19th Century buildings can be just as energy efficient as new construction, and in many cases even more energy efficient. (Perhaps not surprisingly, studies have also shown that buildings built in the 1950’s through the 1970’s were the biggest energy consumers of all.)
The historical wood windows in your building contribute to that energy efficiency and, contrary to urban legend, new replacement windows are not more energy efficient than historical wood windows. Typically, studies that conclude such a finding have compared new replacement windows with historical windows that
have not been maintained or restored, are decaying, and have no complementary energy retrofits such as weather-stripping and storm windows.
If you would like to read these studies, you can access them in the resources section of our website.
Studies on energy efficiency also usually fail to consider “embodied energy”. Embodied energy represents the energy it took to manufacture a product. They say the greenest building is the one
already built when you consider this embodied energy – an existing energy investment that will never be able to be recaptured once you destroy the product it’s embodied in.
If the greenest building is the one already built, then the greenest window is the one already there. Historical wood windows have an embodied energy value that includes all the energy from harvesting and milling the wood to transporting and manufacturing the windows to installing them in your historical building. Preserving existing windows conserves that embodied energy and reduces the use of additional energy when making replacement windows.
Which means that when you take all energy, energy expended on heating and cooling costs as well as the embodied energy, into consideration for defining the energy efficiency of windows – historical wood windows are far more energy efficient than replacement windows