08 Sep 2025 New windows will enhance historic authenticity and efficiency in the Old Corner Bookstore
Here, our Senior Project Manager, Lisa Lewis, provides some insight into the process of identifying new windows for the Old Corner Bookstore complex that would be both historically appropriate and increase the buildings energy efficiency. Historic Boston Inc. has been working with Mass Design Group to find an innovative, energy-efficient, and historically authentic approach to bring the entire OCB complex into the 21st century.
The Old Corner Bookstore complex will soon be sporting brand new, super-efficient windows fitted with innovative vacuum insulated glass. The existing windows were installed in the 1960s and 1970s when Historic Boston acquired the complex, so they are not original to the building. Our current windows are single pane and at the end of their useful life, so when HBI began planning improvements to this important Boston Landmark, we knew the windows needed to be our first priority. HBI was awarded a generous Community Preservation Act grant of $500,000 from the Community Preservation Committee which allowed for this work to begin, in addition to being awarded historic tax credits from our Massachusetts Historical Commission.
New windows must be historically appropriate to the four structures that date from 1718-1828. Here, HBI is demonstrating that it is possible for historic buildings to meet and even exceed modern sustainability building codes. MASS Design helped us evaluate our options for windows that would be both historically appropriate as well as energy efficient. We first considered using windows with double glass panes fitted with a spacer bar between the two layers of glass, which mimics the appearance of true divided lite, double hung windows that have been used for generations. These windows are frequently used in historic buildings and are generally accepted as a good option for preservation projects. Our long time HBI board member and preservation architect, Henry Moss, encouraged us to consider windows fitted with vacuum insulated glass, which performs even better than double paned glass. Research led to discovering Heirloom Windows, which specializes in exactly what we were looking for – high performing wood double hung windows that not only exceed the performance of double pane windows, but also looks more authentic. This is achieved by using two panes of 1/8” glass sandwiched together; the air between the layers is vacuumed out, creating an airtight seal. Between the two layers of glass is a barely visible grid of ceramic “micropillars” that prevent the layers of glass from touching each other. The result is glass that performs at a u-value of about .09 vs. double paned glass that performs at .29. Historically appropriate muntins are then applied to the glass, resulting in a window that appears very close to the complex’s original windows. Heirloom Windows explains their approach to vacuum insulated glass in a brief video here.
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