What Is A Building Envelope?

By March 19, 2020May 7th, 2020LEARN

FabriTec Structures specializes in lightweight structures that make people say, “Wow!” When people see Allianz Field, or BC Place Stadium, or Oceanus Casino, they ask, “How is that made? How can I make a structure look like that?” These structures utilize tension membranes as a building envelope.  These can be in the form of fabric, fabric mesh, or ETFE foil.  In order to provide an understanding of what a building envelope is, how it’s made, and what uses it has, FabriTec Structures will be providing a Q&A on building envelopes. Answering some of the most frequent building envelope questions is Erik Jarvie, Vice President of Business Development at FabriTec Structures.

What is a building envelope/enclosure?

By definition: A building envelope is a barrier between the interior and exterior of a building designed to control the transference of air, water, heat, light, and noise. A building envelope is the exterior of a building and includes the outer walls, roofing, and foundations.

A building envelope typically performs three functions: separate the interior of a structure from the outside world, control various elements inside the structure such as natural light and temperature, and provide the structure an exterior visual.

How can a tensile membrane be used as a building envelope?

Tensile fabric membranes can be featured as either a component or as the primary material of the walls and/or roof of a structure. When utilized as a component, it will typically be applied as the outside layer that is visible from the exterior of the structure. The membrane is the “skin” that wraps a building and separates the inside from the outside. There are several methods available to create a building envelope(enclosure) with a membrane structure, including thermally-insulated ETFE cushion systems.

How effective are tensile membranes at performing the functions of a building envelope? Does it protect the interior of the structure from outside elements? Does it give the structure a visual appeal?

A tensile membrane can be very effective functioning as a building envelope.  Tensioned fabrics and films are available as waterproofing solutions and can protect interior environments against wind, rain, and snow. A single membrane will help stop the air transfer through to the interior, but typically only has an R-value of 1. An ETFE membrane cushion system with multiple layers may reach an R-value of up to 3. Fabric Mesh fabrics can be used to control the amount of light entering the building while still providing visibility to the outdoors. Blocking sunlight (thermal gain) before it enters windows or curtain walls of a building will significantly reduce the solar heat gain and save on energy requirements. Acting as the outermost layer of the building envelope, the fabric mesh membrane can define the look of the building. Fabric mesh membranes offer design freedom in terms of geometry, texture, color, printed graphics, and lighting options.

Can different material types be used for a building envelope on the same structure?

Yes, structures feature a variety of materials for building envelopes all the time. If you think of a house, it has a concrete foundation, brick and drywall walls, doors, windows, and a shingled roof. The same can be applied to most structures. A structure can have a concrete foundation, aluminum and glass curtain wall, and a fabric roof. Tensile membranes are very compatible with a variety of other materials, allowing designers to mix and match materials in a multitude of ways to create an entirely unique structure.

Does the building envelope have to encompass the entire building?

Not at all. While in many cases the envelope does encompass the entire building, not every structure will require a complete cover. For instance, the Allianz Field does not have a full roof. This does compromise the building envelope’s ability to control temperature and protect against rainfall; the walls still provide protection from wind and provides the structure with its eye-catching features. In fact, omitting parts of a building envelope can b a part of the visual appeal of the structure, since the openings can provide unique insight into the structure from various viewpoints. Depending on the purpose of the structure, elements such as weather and natural light may be preferred to an enclosed structure blocking out weather and natural light.

What is the difference between a façade and a building envelope?

The building envelope includes all the layers that separate the interior from the exterior of the building. The façade is the outer layer of the building envelope that is visible from the street or open space. A tensile membrane can be used as an interior layer of a building envelope, but in the majority of cases, tensile membranes are used as the exterior façade of the building envelope.

What structures commonly suit tensile membrane building envelopes?

FabriTec Structures has found tension membranes to be ideal building envelopes and enclosures for large, public structures such as stadiums, malls, and casinos. Large structures such as parking structures and glass curtain wall buildings are also trending. The limits of how a tensile membrane can be used as a building envelope are as limitless as the designer’s imagination.