Replacing Windows in Complex Buildings Isn’t About the Window

Managing Risk, Compatibility, and Continuity Across the Envelope

Installing a new window is a straightforward task—on paper. But in aging, occupied, or historically significant buildings, a window replacement project involves far more than the unit being removed or installed.

What appears to be a maintenance-driven scope often turns into a broader exercise in forensic discovery, envelope strategy, and construction phasing. In these buildings, the success of a replacement has less to do with how a window fits into an opening and more to do with how it fits into the systems around it.

Every Opening Tells a Story

Historic buildings, institutional campuses, and older commercial properties often exhibit a wide variety of construction methods—sometimes even within the same facade. These inconsistencies complicate seemingly routine work.

It’s not uncommon to encounter:

• Layers of dissimilar materials behind the cladding

• Varying wall assembly thicknesses

• Unrecorded retrofits or undocumented transitions

• Sealants, fasteners, or insulation methods no longer in use

Before any window is removed, the team must ask: What’s the building really made of, and how is it performing now?

When the Envelope Includes Hazardous Materials

Hazardous materials—particularly asbestos and lead—are a known variable in older buildings. What’s less predictable is where those materials are hiding. Many are concealed behind head flashings, in the sealant around perimeters, or layered into the sheathing system.

Discovery mid-project can stall progress entirely—unless the team is structured to pivot.

In one case, GHP’s field team uncovered asbestos while removing window frames from a hospital building originally constructed in the 1950s. Because licensed abatement professionals were already embedded within the project structure, the team was able to shift scope, reassign trades, and continue demolition without delays or external approvals.

The project stayed on schedule—not because the problem didn’t exist, but because the workflow accounted for it.

Design-Build as a Practical Strategy

There are many reasons to choose design-build delivery: single-point accountability, budget transparency, accelerated timelines. But in envelope restoration work, design-build serves a different purpose: coordination between disciplines when conditions evolve mid-project.

Envelope failures and material incompatibilities are often only discovered during demolition. In a traditional design-bid-build process, these surprises can lead to RFIs, redesigns, change orders, or delays. With a unified team, redesign and implementation happen in real time.

The architects and the construction managers are already on the same team. They already understand the project constraints. And they can adapt without pausing and restarting the project every time a wall is opened.

Phasing Matters

In occupied buildings—especially hospitals, labs, hotels, or academic settings—window replacement is never isolated from operations. Noise, dust, corridor access, temperature stability, infection control—all must be addressed before a single unit is removed.

In multi-building facilities, complexity increases:

• Varying levels of deterioration

• Inconsistent structural backup

• Localized moisture issues not visible from the exterior

Each building becomes its own case study. Phasing isn’t just about logistics—it’s about understanding how each section of the envelope behaves and when it can be safely worked on without disrupting adjacent systems or occupants.

In Historic Structures, Performance and Appearance Must Align

Replacing windows in historic buildings adds another layer of complexity: balancing performance upgrades with architectural integrity and aesthetics. That often requires custom-fabricated systems designed to meet both preservation and performance standards.

Solutions may include:

• Thermally broken aluminum frames custom designed and fabricated to match original profiles

• Low-E glass that meets energy performance without altering visual appearance

• Concealed drainage systems to address hidden moisture issues without visible changes to facade geometry

These aren’t off-the-shelf answers. They’re the result of iterative collaboration—between architects, manufacturers, and field experts who know the tolerances and limitations of real-world installations.

The Window Is Just the Start

In buildings where the envelope has aged, evolved, or been adapted over time, replacing windows isn't a one-for-one task. It’s the start of a broader investigation.

The best projects—those that stay on track and deliver lasting results—are built around integrated teams who can navigate construction, detailing, environmental hazards, and aesthetic requirements without missing a step.

Window replacement becomes the vehicle. The real work lies in understanding what’s behind it.