A new study by Preservation Green Lab, a project of the National Trust for Historic Preservation, shows that saving your old windows is not only the most cost effective, but surprisingly also the most energy efficient -- even when compared with replacement windows.
This study further validates the performance of our net zero energy home when we restored our century old windows. Watch this video to see how we made our old windows more efficient at a fraction of the cost of installing new windows. A case study of our home from the Clean Energy Coalition showed an astonishing 70% reduction in air-leakage by repairing the old windows and adding low-E glass storm windows. Read my article about the impressive results from our window restoration project.
Energy efficiency: retrofitting old windows vs. replacement windows
The Preservation Green Lab study built on previous research comparing energy and cost savings among different window improvement options and across several different parts of the country. The verdict was that "a number of existing window retrofit strategies come very close to the energy performance of high-performance replacement windows at a fraction of the cost."
Interior window panels, exterior storm windows and cellular blinds, like our Ecosmart Shades, or even a good storm window often perform as well as very expensive replacement windows. The most impressive finding in the study was that climate regions didn't change the results. Restoring old windows appears to be far more cost-effective than replacement windows in virtually every region of the country, even in cold climates like my home in Michigan.
I firmly believe that only in rare cases should you replace your old windows. According to window restoration expert Lorri Sipes, the best windows ever made at any time in history were between the 1850s and 1930s. They are simple, elegant, easy to maintain, and are infinitely repairable. She says a good old window properly maintained will last for centuries.
Bottom line: you probably don't need new windows. Start by consulting a local window restoration expert and discuss your options. Restoring old windows and adding inexpensive weatherstripping to your old windows will stop most of the energy and money loss. Then consider adding interior or exterior storm windows and some high-quality cellular blinds. Your bare toes will thank you this winter.
Thanks to the great work of Preservation Green Lab, we're learning how to make old homes both energy-efficient and cost-saving.