What Is A Building Envelope? Definition, Components, and Importance

What is a building envelope?

In a nutshell, a building envelope is the primary barrier between the interior and exterior of the building. This includes the building’s windows, walls, roof, and foundation. These components each play a role in keeping out the elements, reducing outside sounds, and improving the overall durability of a building. 

What Are the Key Components of a Building Envelope?

Walls, floors, foundations, windows, and doors all make up the building envelope. The effectiveness of the envelope is dependent on the quality of these materials, affecting lighting, ventilation, and energy usage. 

Walls serve multiple purposes within a building envelope. In addition to adding to the overall envelope goal of keeping out unwanted elements, walls also provide insulation and structural support

Why Is the Building Envelope Important for Building Performance?

Building envelopes serve both functional and aesthetic purposes, as an attractive envelope increases the overall curb appeal of a building, while a well-implemented envelope increases the overall comfort of those inside the building.

In general, the building envelope serves four purposes:

• Thermal regulation: walls, roofs, insulation, doors, and windows all play a part in maintaining a comfortable interior temperature.
• Weather resistance: a solid building envelope keeps out the wind, rain, and other natural elements.
• Moisture barrier: while maintaining temperature and keeping out the weather, the building envelope prevents internal damage from water seeping in and causing long-term damage.
• Structural support: a building’s envelope includes the frame and other load-bearing structural elements.

How Does the Building Envelope Impact Energy Efficiency?

Unlike older buildings, modern buildings, and their envelopes are built with energy efficiency in mind. In both residential and commercial buildings, modern envelope technologies account for nearly 30% of a building’s consumed energy, according to the Better Buildings Solution Center of the U.S. Department of Energy. A solid building envelope impacts energy efficiency in a variety of ways.

Thermal Regulation

The primary energy-reduction function of a building envelope is thermal regulation. A properly sealed and insulated building envelope, with proper insulation, energy-efficient doors and windows, and proper airflow goes a long way toward both maintaining a comfortable interior as well as reducing energy usage.

Lighting

Energy consumption may also be reduced through the use of natural lighting through the building envelope. Energy-efficient skylights and windows reduce the need for artificial lighting during daylight hours, cutting down on electric costs, especially in high-traffic commercial structures operating 24 hours a day.

Certain eligible commercial buildings may be eligible for a tax deduction to offset some of the costs of the equipment under Internal Revenue Code (IRC) Section 179D, which was expanded under the Inflation Reduction Act of 2022. In addition to improvements to the building envelope, eligible improvements under the deduction include interior lighting, HVAC, and hot water systems. For more information, check out Energy Star’s website.

What Are Best Practices in Building Envelope Design and Maintenance?

Preventing Water Damage

A good building manager should keep their building envelope up-to-date, starting with addressing one of the most common damaging elements: water. 

Keeping water out of the building starts at the roof and goes down to the foundation. Keeping a commercial roof properly maintained, and ensuring efficient drainage away from the structure at the ground level. Incorporating air and vapor barriers to control moisture and prevent condensation is imperative to avoid mold and other water-focused deterioration.

Ventilation

Poor ventilation raises multiple issues, not limited to mildew and water damage. Ventilation is also key to maintaining a balance between energy efficiency and air quality. 

Insulation

Insulation and sealing are key to internal thermal regulation, but insulation needs vary wildly depending on building location and climate. For example, a building in a colder climate has higher insulation needs than one in a warmer climate, and the building envelope should reflect this need.

Building Envelopes in Commercial Buildings

Generally, building envelopes in commercial buildings are scaled for higher loads and higher energy usage than residential buildings. Unlike residential buildings, many commercial buildings are in use 24 hours a day, increasing the need for efficient, low maintenance, and structurally sound building envelopes.

Materials

A primary difference between residential and commercial buildings is the choice of materials. While residential buildings are also built with durability in mind, commercial buildings tend to be subject to higher levels of wear and tear over their lifetime. 

Commercial buildings may use stronger and more durable materials, such as concrete, steel, and glass curtain walls, while residential buildings may lean toward wood framing and siding. Residential buildings still use durable materials, but maintenance may be simpler due to decreased traffic and lighter wear.

Scale

Additionally, commercial buildings are normally significantly larger than residential buildings, which not only increases material costs but also means that commercial buildings have more of a footprint exposed to the elements, with more chances for damage.

At the larger scale of many commercial buildings, contractors and building owners must balance efficiency, durability, and cost.

Liability

Unlike a single-purpose residential building, commercial buildings may serve multiple purposes within their walls. As such, the building envelope would need to reflect that, as tenants may have different needs including ventilation, lighting, structure, etc.

With increased complexity comes increased risks. A well-made building envelope reduces liability by reducing the chance of damage across a varied structure.