Window Wall vs. Curtain Wall? An In-Depth Analysis of Differences

Stunning exteriors and light-filled interior spaces are popular design benefits of both window wall and curtain wall design. The versatility of these two design options allows architects to create visually striking facades suitable for a variety of architectural styles.

These systems can also enhance energy efficiency through advanced glazing technologies and insulation options. Their adaptability and use in iconic structures worldwide have solidified their status as much-desired architectural solutions.

Understanding Window Walls

A window wall is a building facade system that combines large, often prefabricated windows with opaque spandrel panels, to create the appearance of an uninterrupted glass surface. Unlike traditional punched windows, window walls cover large sections of a building's exterior and can be multiple stories in height. Key characteristics of a window wall system include:

Integration of Windows

Window walls incorporate large windows or glass units to provide expansive views, natural light, and a modern aesthetic.

Structural Support

Unlike curtain walls, window walls are partially supported by the building's structural framing. They rely on the structural system for stability.

Spandrel Panels

For a consistent exterior appearance, spandrel panels are often used between windows. They can be opaque and are usually made of materials like metal or glass to match the overall facade.

Sealing and Weatherproofing

Proper sealing and weatherproofing are essential to prevent air and water infiltration. Sealants and gaskets are used to maintain a watertight and airtight enclosure.

Thermal Performance

To meet energy efficiency standards, window walls often incorporate insulated glass units (IGUs) and thermal breaks to reduce heat transfer.

Installation

Window wall installation can be faster and more cost-effective than curtain wall installation, as they are often assembled on-site from pre-fabricated components.

Window walls are commonly used in residential and mid-rise commercial buildings to provide a modern, open feel while maximizing natural light and views. However, they are structurally less versatile than curtain walls and rely on the building's structure for support.

Understanding Curtain Walls

A curtain wall is a non-structural building facade system primarily composed of glass, metal, or other materials that is erected much like a curtain or covering of the exterior of a building. Unlike windows walls, curtain walls are non-load-bearing. Key characteristics of a curtain wall system include:

Glass Panels

Curtain walls consist predominantly of glass panels, which are often large, and they can span from floor to ceiling to offer unobstructed views and natural light.

Non-Structural

Curtain walls are not designed to carry the building's structural load. Instead, they are attached to the building's frame or structure, and serve as an outer covering.

Versatility

Curtain walls offer design versatility, to allow architects to create visually distinctive and customized building facades, by incorporating different types of glass, finishes and colors.

Weatherproofing

Sealants, gaskets, and thermal breaks are used to maintain a watertight and airtight enclosure.

Thermal Performance

To meet energy efficiency standards, curtain walls typically include IGUs and thermal breaks to minimize heat transfer.

Installation

Curtain walls are typically assembled from pre-fabricated components, which can be transported to the construction site and installed. This approach can expedite the construction schedule, as well as improving cost-effectiveness.

Spandrel Panels

To maintain a consistent exterior appearance, opaque spandrel panels are often incorporated between the glass panels in order to provide a uniform aesthetic.

Curtain walls are commonly used in modern commercial and high-rise buildings to achieve a sleek, contemporary appearance while maximizing daylighting and energy efficiency. Their non-structural nature allows for innovative architectural designs and the creation of distinctive skyscrapers and modern structures.

Comparing Window Wall vs. Curtain Wall

Both window walls and curtain walls provide dramatic design options. While curtain walls provide more design flexibility and better thermal performance, window walls offer operable windows for natural ventilation. Curtain walls are common in commercial buildings, while window walls are often used in residential and mixed-use structures.

Choosing the best option for a project depends on design requirements, such as aesthetics, energy efficiency, and budget.

Aesthetic Differences And Design Possibilities

Window walls emphasize a continuous glass surface with vertical mullions between windows, for a sleek and modern appearance. They are well suited to projects where a seamless, panoramic view and abundant natural light is desired. Window walls have a limited range of structural and design options.

Curtain walls, on the other hand, provide a versatile canvas for architects. They can incorporate various glass types, spandrel panels, and finishes, for endless design possibilities. While curtain walls also promote natural light, they allow for more creativity in creating distinctive facades. They are favored for iconic and architecturally unique buildings, and can create a wider range of aesthetic expression.

Performance Aspects: Energy Efficiency, Insulation, and Thermal Control

Both window walls and curtain walls can achieve energy efficiency and thermal control, but they differ in performance options.

Window Walls

While they offer good insulation with double or triple glazing, window walls are generally less thermally efficient than curtain walls due to their larger glass-to-frame ratio. To enhance performance, low-E coatings, gas fills, and thermally broken frames can be incorporated.

Curtain Walls

Curtain walls excel in thermal control and insulation. They allow for thicker IGUs, thermal breaks, and advanced glazing technologies, for superior energy efficiency. Curtain walls are often a preferred choice for projects prioritizing energy savings and sustainability.

Installation and Cost Considerations

Window walls typically have lower insulation value due to more extensive glass areas, which can potentially lead to higher heating and cooling costs in the long-term. They are often more cost-effective upfront, as they can be assembled on-site from pre-fabricated components in order to reduce labor expenses.

In contrast, curtain walls offer superior insulation options with thicker glass units and thermal breaks, resulting in better thermal performance and potential energy savings. However, their initial costs can be higher due to materials and potentially complex installation.

Choosing between the two depends on project priorities, budget constraints, and the desired balance between upfront costs and long-term energy efficiency.

Maintenance And Durability

Typically, window walls require more maintenance than curtain walls due to their larger glass surface, which can accumulate dirt and require regular cleaning. They may also be more vulnerable to damage from environmental factors that can impact their long-term durability. The durability of window walls can vary depending on factors such as the quality of materials used and the climate in which the building is located. Over time, exposure to UV radiation and environmental pollutants can also affect the longevity of sealants and gaskets.

Curtain walls often require less maintenance than window walls, as they incorporate spandrel panels that reduce the exposed glass area. The choice of materials, like durable aluminum framing, enhances their longevity and resistance to weather and wear. Properly designed and maintained curtain walls have a long lifespan and offer better protection against moisture infiltration than window walls.

While both window walls and curtain walls can be designed and constructed to meet specific maintenance and durability requirements, curtain walls often offer advantages in terms of reduced maintenance needs and enhanced durability based on design features and materials. Ultimately, the choice depends on project goals, as well as climate and budget considerations.

Sustainability and Environmental Impact

Both window walls and curtain walls can be sustainable depending on design, materials, and energy efficiency features. Curtain walls have an advantage in terms of potential energy savings, durability, and material choices that align with sustainability goals.

Window Walls

Window walls can offer sustainability benefits through natural daylighting, which potentially reduces energy consumption for lighting. However, extensive glass areas may impact heating and cooling efficiency, depending on the glazing and framing choices. Additionally, regular cleaning and maintenance can have environmental consequences.

Curtain Walls

Curtain walls have potential sustainability advantages. They allow for high thermal performance, and can reduce long-term energy needs for heating and cooling. The use of recyclable aluminum enhances eco-friendliness. Additionally, well-designed curtain walls can optimize natural lighting.

Case Studies

801 South Skinker Boulevard Building, St. Louis, MO

The 801 South Skinker Boulevard Building in St. Louis exemplifies International Style architecture, drawing inspiration from the modernist architect Mies van der Rohe.

Erected in 1960 by St. Louis construction magnate I.E. Millstone, the building served as Millstone's residence for three decades. With its floor-to-ceiling window wall design, the building offers panoramic views of the adjacent Forest Park, which at twice the size of New York's Central Park, holds historical significance as the site of the 1904 St. Louis World's Fair. The renovation project included Winco 1450 Series high performance 4”-deep fixed architectural windows with project-in hopper vents, to replace the 739 original windows in the 18-story window wall glass structure.

Norton Suburban Hospital, Louisville, KY

The Norton Suburban Hospital faced construction delays on a critical project aimed at enhancing healthcare services for women and children. Initially planned as a stick-built and field-glazed endeavor, the project fell behind schedule. A persuasive proposal from GAP introduced the idea of a pre-glazed unitized curtain wall system, which prompted a reconsideration by the hospital and architects.

Collaborating closely with GAP, they adopted the pre-glazed, unitized curtain wall approach. This innovative system allowed for the installation of fully assembled and glazed panels, and reduced the installation timeline from months to days. With more than 52,000 square feet of curtain wall required, Graham Curtain Wall Solutions provided on-site support, including training in the field. The project concluded successfully in December 2014, and exceeded the owners' expectations.

Find the Ideal Curtain Wall or Window Wall for Your Project with Acelab

Acelab is a cloud-based collaboration platform that offers a range of tools and resources to help architecture professionals research, compare and select building products for their projects. With Acelab, users can access product data, technical specifications, and CAD details from leading manufacturers, as well as tools to create and manage project libraries, product lists, and specification documents.

Acelab is designed to help architecture professionals save time and streamline their workflows by providing a centralized source of information and tools for building product research and specification tasks.