Windows are often a dominant architectural feature in old houses. A six-over-six sash with wavy, bubbled glass has a charm that modern windows can only aspire to, more than offsetting their less-than-stellar energy performance.
Or so many local historical preservation committees would argue. And, as Mike Keesee has discovered, that’s a frustrating problem for builders and homeowners who want to make energy-efficient windows part of a renovation.
Writing in a Q&A post at GreenBuildingAdvisor, Keesee says his local historic preservation committee just doesn’t get it.
“Our local historic preservation committee will not allow retrofits/replacement of so called historic windows — the aging, single-pane, wood frame with ‘wavy’ glass,” Keesee writes.
“Some in the historic community claim that the existing windows can be retrofitted with films, weatherstripping, insulated shades or the like and match the performance of a high-performance (e.g., Energy Star rated) replacement window. Unfortunately, they don’t respond well to arguments based on the laws of physics.”
Keesee’s appeal for studies that quantify the benefits of replacing old windows with new ones is the subject of this week’s Q&A Spotlight.
Energy losses are easy to prove
Matthew Nolette has been researching exactly this question and has facts in hand that would support Keesee’s point of view.
“As it turns out, I just spent the last couple of hours trolling NFRC [National Fenestration Rating Council] data for specifics on the performance of a single-glazed wood window with a combination storm window applied,” Nolette says.
A double-hung window with 1/8-in. thick clear glass separated by a roughly 2-in. air gap from a single low-e combination storm has a U-factor of 0.35, Nolette writes. That U-factor is 25%…