What is Fenestration? Types and Roles in Buildings

In architecture, fenestration refers to the openings in a building’s envelope, most notably the windows, doors, skylights and curtain walls. In layman’s term, fenestration is anything that allows for passage from outside to inside. Fenestration is usually viewed as an aesthetic feature, but it also affects the performance of the building. For example, a strategically placed window can considerably increase natural lighting, reduce the usage of indoor lighting fixtures, and thus save electricity. They can also be used for passive solar heating for reducing the workload on space heating systems.

Now that you know about fenestration, lets dive into the main types of fenestration in commercial buildings along with their roles.

1. Curtain Walls

Curtain walls are thin and lightweight, typically aluminum-framed walls, containing glass in-fills, metal panels or thin stone. These walls are attached to the building structure, but they do not carry any floor or roof loads. The wind and gravity load of curtain walls are transferred to the building structure, usually at the floor line. These walls can vary from manufacturer’s standard catalog systems to specialized custom designs.

Based on their fabrication and installation techniques, curtain walls are classified into 2 categories:

• Stick System: The curtain wall frame, also called as mullions, and glass panels are installed piece by piece in stick system.
• Modular System: The curtain wall is made up of large units, also called modules, which are assembled and glazed in a factory before getting assembled on the building site.

Consulting to a professional with expertise in curtain wall is recommended for installing a curtain wall successfully. Careful integration of curtain wall with adjacent elements like roofs, wall bases and claddings in crucial.

1. Windows

Windows are wall openings in the building’s façade that allow light and air flow, while providing the outside view for the occupants, and are usually fitted with glass frames. Some other common window frame materials include fiberglass, aluminum, vinyl, wood, steel and PVC. Aluminum frames are most popular as they provide design flexibility. In residential buildings, fiberglass, wood and vinyl frames are commonly used.

Windows can be fixed or operable or a combination of both based on the building design and the surrounding environment.

• Fixed windows offer higher resistance to air and water infiltration. They also require less maintenance, and are used where natural ventilation isn’t needed. Fixed windows consist of a frame with and infill sealed together.
• Operable windows are idea where natural ventilation is required. They consist of a frame and sash that are sealed together by weather-strips. They are classified into sliding seal windows and compression seal windows.
  

1. Exterior Doors

Door mainly serve as entryways and exits in buildings, used by public and also private service entrances. There are 3 main types of door:

• Revolving doors, serving entrance and exit purposes
• Swing doors, serving entrance and exit purposes
• Industrial doors, serving material handling and security purposes

Commonly used door materials are steel, aluminum, wood and glass. In commercial buildings and stores, aluminum frames are typically used with glass in-fill. However, industrial doors are not for pedestrian access, and are used for material handling with the main function of providing security. This type of system is not frequently designed in commercial building envelope.

1. Skylights

Skylights, also known as sloped glazing systems, are used for providing daylight. According to the WELL building standard, daylight has a positive effect of psychology of the occupants, and also provide energy saving measures. They have 2 basic components; supporting members and infill panels.

Several design considerations are taken into account before installing skylights. For eg. skylights experience a lot of solar heat gain during summers and heat loss during winters. Due to this, thermal conditions must be considered during HVAC design.

Another important aspect is moisture resistance. Since skylights are a part of the roof, they are exposed to rainwater, which makes them susceptible to water leakage. A drainage system must be incorporated to collect the leakage. This can also be used for rainwater harvesting.

1. Glazing

Glazing is a term used for “glass”, which is a part of building fenestration. Glass is one of the most common construction materials, and has been used for centuries to provide natural daylight in buildings. The following are the most commonly used types of glasses in buildings:

• Architectural glass: These are available in 3 different strength categories: annealed, heat-strengthened, and fully tempered glass. These categories are ordered from lowest to highest in strength and durability.
  
• Laminated glass: It consists of 2 or more glass surfaces adhered together with a plastic interlayer for providing good thermal and acoustic insulation.
  
• Coated glass: This type of glasses is used to improve thermal performance, and have low emissivity coatings.
  
• Tinted glass: This type of glasses contains minerals that promote light absorption.
  
• Insulating glass units: This type of glasses consists of 2 or more glass layers that are separated with spacers, which enclose a sealed air space with desiccant. This allow superior thermal performance and acoustic properties.