Renovation Retrofit

More than 50 percent of American Institute of Architects members’ billings are for renovation and reuse projects, according to an April 2024 report. This trend will likely continue since approximately half of all U.S. commercial and institutional buildings were constructed before the 1980s.

The majority of existing U.S. buildings are expected to remain in use until 2050 and, eventually, will require renovation. Adding urgency, the U.S. Department of Energy (DOE) has issued a national blueprint to decarbonize the building sector by 90 percent by 2050. The DOE’s plans to increase energy efficiency and minimize emissions include retrofitting millions of window systems.

Aluminum is the material of choice when renovating buildings’ windows, storefronts, curtain walls, entrance systems, and other fenestration systems. Versatile for forming and fabricating, aluminum can be shaped and finished to match existing openings and historical standards. Infinitely recyclable, aluminum supports environmental and sustainability goals.

Modern aluminum-framed fenestration is manufactured with thermal barriers and durable finishes for improved performance, energy efficiency, and resiliency. Installed and maintained correctly, these systems have a lifespan of up to 40 years or longer. At the end of their use on the building, aluminum can be locally recycled.

The first step in a successful fenestration replacement is to enlist a design professional to set aesthetic and performance goals. Thermal transmittance, condensation resistance, acoustics, ventilation, view, and solar heat gain should all be considered. It is often advisable to include the building’s mechanical engineer and technical staff from a qualified window manufacturer in establishing performance criteria.

Improved performance

Many aging buildings’ existing windows are still leaky, single-glazed units with conductive framing systems. Federal and local incentives have boosted interest in upgrading fenestration performance to improve buildings’ sustainability, energy efficiency, and resiliency.

When high-performance fenestration replacement is paired with modernizing electric HVAC or lighting systems, it can yield savings in equipment and utility costs and long-term reductions in natural resource consumption and greenhouse gas emissions.

Using high-performance glazing and thermally broken aluminum-framed fenestration reduces unwanted heat energy transmission. It enhances occupants’ comfort and well-being by managing interior temperatures, eliminating drafts, reducing noise, and improving condensation resistance. Without leaks and condensation, mold, mildew, and other microorganisms are also less likely to grow.

Additional wellness benefits with modern fenestration include access to fresh air, daylight, and outside views. For resiliency and security design enhancements, fenestration selection criteria can update hurricane impact resistance, seismic improvements, ballistic and blast hazard mitigation, and forced entry deterrence.

Historic considerations

Local regulations and building codes impact the established performance criteria. Still, in some jurisdictions, the exterior appearance of proposed replacement fenestration can also require redevelopment authorities’ approval, especially in designated historic districts.

The Federal Historic Preservation Tax Incentives have helped preserve more than 49,000 historic properties since 1976. The National Park Service (NPS), through its Technical Preservation Services division, and the Internal Revenue Service administer the program in partnership with State Historic Preservation Offices.

The NPS Technical Preservation Services division issues guidance and information on improving historic properties’ sustainability, energy efficiency, and resiliency while preserving their character. When window replacement is required, and using the same material is not technically or economically feasible, historic properties often are still required to preserve distinctive features, finishes, construction techniques, and matching design, color, texture, and visual quality of the original building components.

Attractive appearance

Aluminum fenestration manufacturers offer a broad range of operating window types with beveled exterior glazing reveals, replicating the look and texture of existing putty-glazed steel, bronze, or wood sash. These are available with matching beveled muntin grids. In many historical projects, the windows being replaced are tall, double- or triple-hung sashes used for natural daylighting in buildings and were constructed before the advent of efficient electrical lighting.

These tall, hung sashes get heavy when upgraded from single-glazing to double- or triple-glazing. Projected aluminum-framed windows offer an easy-to-operate alternative. As the name implies, projected windows operate by “projecting” inward or outward from the plane of the wall as casements, awnings, or hopper vents. Projected windows can be engineered with the “offset” glass plane appearance of hung sash and aluminum frame. This preserves the intended appearance and maximizes the investment through reduced maintenance and repair expenditures without sacrificing modern performance.

When original windows are weather-tight and ventilation operation is not required, adding high-quality, custodian-operable interior accessory windows (IAWs) can be a viable option. With appropriate caution to avoid between-glass condensation, these economical add-on units improve control of sound, energy, air, and light while leaving existing windows undisturbed.

For major renovation projects, installation of in-situ samples is highly recommended. Not all stakeholders can visualize how new windows will look and operate just by reviewing architectural drawings and specifications. Site samples offer first-hand experience in field measuring, removal, and replacement logistics. If multiple manufacturers’ products are being considered, hands-on comparison of products in their installed condition is made possible.

Installation logistics

The critical logistical decision the window replacement contractor faces is whether to leave existing window frames in place or do a complete “tear-out” and start again.

Removing the existing operable sash while leaving existing framing in place usually makes for a much faster installation process and minimizes disruption to occupants. The existing frames are anchorage points, and an extruded aluminum sub-frame or “panning” system lines the opening. This panning system is a “frame around the frame” of the new window. It can be extruded to incorporate decorative ogee, reverse cove, or custom geometry for an attractive, historically influenced exterior appearance.

If a tear-out of existing frames is opted for, perimeter protection is often required in occupied spaces, and the process is slowed considerably. Caution must be exercised in determining what concealed wall materials may be disturbed, including asbestos. These cases require the involvement of abatement specialists. With complete tear-out, sightlines are reduced for maximum daylight area, new anchors can be more securely attached, and seals can be made directly from new window frames to existing wall substrates.

In either case, extruded aluminum interior trim is available in many shapes and sizes to finish the opening when replacement is complete.

Perhaps no other building update can add so much to the performance, comfort, and image of an existing property than upgrading its fenestration systems. Careful selection of product type and manufacturer, complete and accurate contract documents, and coordination with owners and occupants will result in a successful project.

Lisa May is the architectural and preconstruction services director for the EFCO, Tubelite, and Alumicor brands of Apogee Enterprises. She has 25 years of experience working with architects and building teams on commercial, institutional, and high-rise residential projects. May can be reached at lmay@apog.com.