Curtain Walls Explained
Curtain walls provide a clean, contemporary look that enhances the visual appeal of buildings as well as the interior living space. The extensive use of glass and minimalistic framing create an elegant facade that stands out in both rural and urban landscapes. These non-structural outer coverings of a building offer several advantages, including improved energy efficiency, enhanced aesthetics, and increased natural light.
Historical Evolution
The concept of curtain wall windows emerged in the early 20th century, coinciding with advancements in steel and glass manufacturing. Traditional building facades were load-bearing, meaning they supported the weight of the structure, not just the windows. However, the development of steel skeleton frames allowed architects to design buildings where the external walls no longer needed to bear structural loads. This innovation led to the creation of curtain walls, which are attached to the building's framework but do not carry any structural weight.
One of the earliest and most iconic examples of curtain wall architecture is the Lever House in New York City, designed by Gordon Bunshaft of Skidmore, Owings & Merrill. This modernist skyscraper featured a sleek glass and steel exterior, setting a new standard for commercial architecture and paving the way for widespread adoption of curtain wall systems.
The Lever House in New York City, built in 1952 utilizes a glass and steel curtain wall system.
Design Principles
Curtain wall windows are constructed using aluminum or steel frames which support glass panels (IGUs). The frames provide a lightweight and durable structure to support the glass, while the glass panels offer transparency and aesthetic appeal. The key design principles of curtain wall windows include:
Non-Structural Nature: Curtain walls are attached to the building's structural frame, allowing for greater design flexibility. This non-structural nature enables architects to create large, uninterrupted expanses of glass, providing unobstructed views and abundant natural light.
Modularity: Curtain wall systems are often fabricated in modules, which can be easily transported and assembled on-site. This modular approach not only speeds up construction but also ensures higher quality control and precision. Installers often refer to putting curtain walls together like working with legos.
Weatherproofing: Effective weatherproofing is built into the curtain wall system. Sealants, gaskets, and drainage systems are integrated into the curtain wall design, preventing water infiltration and air leakage, ensuring the building remains watertight and energy-efficient. Additional waterproofing is only required around the outside edges of the curtain wall.
The Schuco FWS 50.SI curtain wall has a 50 mm wide face width.
Benefits
Thermal Performance: Modern curtain wall systems are designed to enhance a building's energy efficiency. They incorporate thermal breaks within the frames and use double or triple glazing with low-emissivity (lowE) coatings to reduce heat transfer and improve insulation. With an efficient thermally broken frame, triple pane glazing and LowE coatings the u value of a curtain wall can go down to 0.16 Btus/6.25 R value.
Natural Light Penetration: The large panes of glass and minimal frames allow natural light toi infiltrate the dwelling. Visible light transmittance and solar heat gain can be controlled through the use of LowE coatings and blinds.
The Jansen VISS Facade system provides slim dimensions allowing natural light to penetrate buildings.
Acoustic Performance: Modern curtain walls can be designed to provide excellent sound insulation, reducing noise pollution from the outside and enhancing the acoustic comfort of indoor spaces.
Resistance to Environmental Stresses: Properly engineered curtain walls can withstand significant wind loads, seismic forces, and other environmental stresses, ensuring the structural integrity and safety of the building.
Greenness: By enhancing energy efficiency and reducing reliance on artificial lighting and climate control systems, curtain walls contribute to the overall sustainability of a building. This helps in achieving green building certifications and reducing the building's carbon footprint. Passive Haus Certified curtain wall systems are available from Schuco and Jansen.
Many curtain wall systems use materials that are recyclable and have a lower environmental impact, further contributing to the sustainability goals of the project.
Considerations
Despite their numerous benefits, curtain wall windows present certain considerations.
The installation of curtain wall systems requires an experienced installer with specialized skills and precision.
While curtain walls themselves are non-structural, they must be securely attached to the building's structural frame. This requires careful planning and engineering to ensure the curtain wall can withstand wind loads, seismic forces, and other environmental stresses.
Curtain wall systems offer many benefits that make them an essential component of contemporary architecture. From enhancing the aesthetic appeal and increasing natural light to improving energy efficiency and providing durability, these systems contribute to creating functional, comfortable, and sustainable buildings. While there are challenges associated with their installation and initial cost, the long-term advantages of curtain wall systems make them a worthwhile investment for many architectural projects. As technology continues to advance, the capabilities and benefits of curtain walls are likely to expand, further cementing their role in shaping the future of building design.