Fenestration systems refer to all openings in the building envelope, including curtain walls, windows, doors and skylights. Fenestration is typically viewed as an aesthetic feature, but it also affects building performance. For example, smart window placement can increase natural lighting, reducing the use of light fixtures and saving electricity. Fenestration can also be used for passive solar heating, which reduces the workload on space heating systems.
This article provides an overview of the main types of fenestration and common glazing options used in commercial buildings.
Curtain walls
Curtain walls are thin and typically use aluminum frames, containing glass infills, metal panels or thin stone. The frame is attached to the building structure but does not support floor or roof loads. These walls are mainly subject to wind and gravity loads, which are transferred to the building structure at the floor line. Curtain walls can range from standard manufacturers' catalog systems to specialized custom designs.
Curtain walls can be classified into two categories based on their manufacturing and installation method: stick systems and modular systems.
- Stick systems: The curtain wall framing, also known as mullions, and the glazing or panels are installed piece by piece.
- Modular system: The curtain wall is made up of large units (modules) that are assembled and glazed in the factory and then assembled on site.
Consider that curtain walls generally comprise only part of a building's wall system. To successfully install a curtain wall, careful integration with adjacent elements such as roofs, cladding and wall bases is crucial.
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windows
Windows are openings in walls, usually fitted with glass frames to allow light and air in while providing a view for occupants. Some common materials for window frames include aluminum, fiberglass, vinyl, steel, wood, and PVC. Aluminum frames are the most popular and offer design flexibility as they are available in various shapes, designs and colors. In residential construction, wood, vinyl and fiberglass frames are the most common.
Windows can be fixed, operable, or a combination of both.
- Fixed windows consist of a frame with a sealed filling. They offer better resistance to air and water infiltration and also require less maintenance.
- Operable windows allow for natural ventilation. They consist of a frame and frame that are sealed by caulking strips, in addition to the filling being sealed to the frame.
Operable windows can be broadly classified into slide-seal windows or compression-seal windows. Windows with compression seals tend to provide better air and water resistance because they reduce friction and wear on the weatherstripping.
External Ports
Doors function as the main entrances and exits of buildings, and can be used as public access or private service entrances. There are three main types of ports:
- Revolving doors, serving entry and exit functions.
- Revolving doors, serving entry and exit functions.
- Industrial doors, serving material handling and security functions.
Some commonly used door materials include steel, aluminum, wood, and glass. Doors used in commercial storefronts typically use glass-filled or all-glass aluminum frames. Industrial doors are used for moving materials and not for pedestrian access, and their main function is to provide security. This system is not often designed for building envelope performance, and security grilles are typically installed in commercial applications that require public access.
Skylights
Skylights are also known as sloped glazing systems and are used to provide natural lighting. In addition to providing energy savings, natural light has a positive psychological effect in accordance with the WELL building standard. Skylights are engineered systems assembled from standard or custom extrusions supplied by the manufacturer. Skylights have two basic components, which are the supporting members and the infill panels.
There are several design considerations regarding skylights. For example, these elements experience significant solar heat gain during the summer and heat loss during the winter. For this reason, thermal considerations must be taken into account in HVAC design.
Another important aspect is protection against moisture, as skylights are part of roofs. They are exposed to large amounts of rainwater and are much more susceptible to water leaks compared to vertical fenestration. A drainage system should be incorporated to collect leaks and condensation, and rainwater harvesting is also a viable option.
Glass
Glass is a common building material that has been used for centuries to provide natural light and weather protection in buildings. The following are some of the most common types of glass:
- Architectural glass is available in three different strength categories: annealed, thermoset and fully tempered glass – ordered from lowest to highest strength and durability.
- Laminated glass consists of two or more glass surfaces glued together by an intermediate layer of plastic, providing good thermal and acoustic insulation.
- Coated glass is covered with low-e coatings to improve thermal performance.
- Colored glass contains minerals that color the glass, promoting light absorption.
- Insulating glass units consist of two or more layers of glass, separated by spacers that enclose an air space sealed with desiccant. This space reduces heat transfer, providing superior thermal performance and good acoustic properties.
In new construction, double or triple pane glass can significantly reduce heat transfer through the building envelope. Compared to an uncoated, single-pane glass window, a high-efficiency window can reduce heat gain and loss by more than 70%.
