Michelle Peiffer
Renovating a historic 1930’s brick building presents many challenges. Renovating that same building to exceptionally high energy standards adds further layers of complexity to the project. Fortunately, for a vacant 5,000-square-foot brick storefront, developer Chaden Halfhill has not shied away from these challenges.
Storefront window facing east.
Few of these challenges are as convoluted as maintaining the delicate balance between the respect for the building’s historic character and the integration of modern energy-saving technologies. Halfhill’s renovation pilot project, Green & Main, aspires to LEED platinum certification as it transforms an abandoned grocery building into a first floor business and a second floor residence. As it turns out, windows are a particularly complex piece of the puzzle.
Balance Between Historic and Modern
Located in Des Moines’ Sherman Hill neighborhood, all 54 original windows, including two large storefronts, will be retrofit for energy efficiency in a variety of ways depending upon the condition, location and window type. While the default choice for most developers is often to replace historic windows in order to increase energy savings, most of the windows at Green & Main will be repaired, restored and specially renovated in accordance with the project’s energy efficiency and historic preservation goals.
“It is extremely important to find the balance between historic integrity and modern efficiency,” states Halfhill. “Windows are the place where historic preservation is combined with the goals in improving the efficiency of the building. Sometimes they are inclusive, sometimes exclusive.”
Halfhill recently explained the process of window restoration in detail during this month’s Green & Main Sustainability Renovation Workshop Series. “Windows are the biggest components to both preservation and efficiency,” Halfhill emphasized.
Storefront Windows
Exterior of the building, facing east.
There are two fixed storefront windows facing 19th Street. These windows have been boarded up for a very long time. Removing the boards and restoring the windows will have a huge impact on both the appearance and the character of the building.
During the process of renovation, special care has been made to salvage windows and other pieces of the existing building for a similar use or for repurposing. During removal of the window infill boards, the original wood sill was uncovered. This wood sill will serve as a template for both the window reconstruction and from which the workers will replicate the angles of the old storefront window. While the original look and detailing of the historic storefront will be retained, new double pane insulated glass will be installed. The new panes are required under applicable preservation guidelines to match the appearance of historic storefront glass.
Row of small transom windows.
Above each of the two storefront windows and the entry vestibule, are smaller transom windows that allow more natural light into the building. The original glass had a translucent texture and several remaining pieces were salvaged intact. The salvaged glass was cleaned and sent to a factory where it will be incorporated into new double-paned assemblies. This will increase the R-value, or thermal resistance, while also maintaining the window’s historical appearance. Fortunately for our project, the manufacturer was able to locate new glass with a similar pattern to repair the transom windows that had damaged or missing panes.
Double-Hung Windows
The double-hung windows in the second floor apartment require a multi-pronged approach in order to meet historic preservation guidelines and energy efficiency goals. A double-hung window has two operable sashes – the top sash opens down and the lower sash opens up. This allows air to circulate effectively through a room and minimize the need for mechanical heating and cooling. The benefit in restoring historic double-hung windows is twofold. First, historic windows are “repairable” without specialized products or tools. Second, reuse of existing windows diverts material from landfills.
‘Anatomy of a Window’ See glossary below.
The first step in the process was removing sashes from the window frames. Historic double-hung windows are designed to be “deconstructed” and repaired. Deteriorated lead paint was removed from the windows using a chemical stripper, in accordance with Federal and state guidelines. Removal of the paint allowed workers to better assess the condition of each sash and make the necessary repairs.
Along the way, we also discovered that the weight pockets to the side of older windows have to be rebuilt. The missing sash rope, weights and pulleys have to be located, repaired or replaced to return each window to working order. The final step is to put the windows back together with new glazing, which is the material that holds the glass into the wood frame. It’s a long and exhaustive process to meticulously restore each window, yet Halfhill believes in the importance of keeping these windows out of the landfill.
To optimize the Green & Main building, a double-window assembly was designed. Inside each historic double-hung window will be a new double-hung window. This assembly will create an air-tight seal on the inside while retaining the historic appearance from the outside of the building. The new interior windows will be the same as the historic ones and installed in a new insulated wall construction adjacent to the original masonry wall.
The New Addition
It is important to note that window’s are a major component of a building’s “shell,” and one of the main points that must be examined in an energy retrofit. However, buildings behave as interactive systems where the foundation, walls, windows, doors, insulation and roof work together to keep energy in and weather out.
An important consideration to look at when integrating new windows with an existing building is to pay particular notice to the existing window positioning and reflectivity of the existing windows. With careful deliberation, the building can take advantage of natural wind patterns that can allow for natural cooling of the building. The focus of the window reflectivity is to take advantage of the opportunity to gain solar heat in the winter and keep the building cooler in summer. The new construction on the back of the building will have newer energy efficient windows, but they will correspond well with the positioning of the older windows to achieve maximum energy efficiency naturally: they will be designed to instinctually manage heat and heat loss.
Green & Main storefront window.
All of the components touched on in today’s article require detailed, constant attention as the Green & Main Pilot project continues to evolve. Whole building awareness helps ensure major milestones and decisions to the building envelope itself are made and supported accordingly, resulting in building science at its maximum efficiency.
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Anatomy of a Window Glossary
Upper/Lower Sash: A frame in which the panes of a window or door are set
Rail: A bar extending horizontally between supports, as in the framework of a sash
Head/Side Jam: The straight side of arch, door or window
Stiles: A vertical member of a panel or frame, as in a door or window sash
Parting Bead: A small narrow molding used to separate and guide the upper and lower window sash in Victorian double-hung wood windows
Meeting Rail: The rails in sliding sash windows, which meet in the middle of the frame
Window Sill: The flat piece of weed, stone, or the like, at the bottom of a window frame
– Michelle Peiffer is director of communications strategy for Indigo Dawn.
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