Understanding the Building Envelope

Understanding the Building Envelope


Corner of a brick building with windows

The building envelope is the boundary between a building’s interior and the exterior environment. It is arguably the most important system in a structure. The building envelope assists with occupant comfort and safety, but also contributes to important objectives such as energy efficiency and indoor air quality. At the most basic level, it keeps the weather and water out of a building.

Because of its importance, the building envelope should be carefully specified and defined during the design stage of construction to minimize potential issues. In addition to client input and preferences, budget and intended use, geographic location and environmental factors must also be considered in the design of the building envelope, as many hidden forces are at play. Factors can include the physics of wind movement, stack or chimney effect, exhaust ventilation and more. While it is a vital component of any building, only more recently have building codes begun to reflect the importance of a well-designed building envelope.

At Technical Assurance, we are your building envelope experts. We have extensive critical facility industry experience. Whether you are facing new construction or retroactive upgrades to your existing building, we can serve as your comprehensive building envelope partner.

An important first step in understanding your building envelope is knowing its basic components and their function.

Functions of a Building Envelope

The primary purpose of a building envelope is to create a barrier between the indoors (conditioned environment) and the outdoors (unconditioned environment). The building envelope serves three specific functions:

  1. Mechanical and Load Support – Provides structural support against internal and external loads and forces.
  2. Climate Control – Thermal, air, water and vapor barriers control the exchange of heat, air, water and condensation between the interior and exterior of the building.
  3. Aesthetics – Meets desired design aesthetics on the inside and outside of the building.

Components of a Building Envelope

The building envelope is a system of protective components that surround the entire exterior of a building, from below-grade to the roof.


Wall assemblies consist of a system of components that fulfill the support, control and finish functions of the building envelope. Components typically found in wall assemblies (from exterior to interior):

  • Exterior Cladding – Siding or wall cladding is the protective material attached to the exterior side of a wall of a building.
  • Weather Barrier – The weather barrier is installed outside of the wall structure behind the cladding/siding to provide water protection and airflow control.
  • Exterior Sheathing – Provides a surface on which the cladding materials can be fastened to.
  • Insulation – Helps control moisture, heat, air and sound.
  • Structural Components – Walls are constructed of various support structures that aid in the overall structural integrity of a building.
  • Interior Sheathing – Provides structural strength, but also acts as both an air barrier and vapor barrier.


The roof plays a major role in overall building sustainability. As a critical component of the building envelope, the roof is responsible for providing protection against rain, snow, sunlight, extreme temperatures and wind.

The main functions of a structure’s roof are:

  1. Water Protection – To shed water and prevent it from ponding on the roof surface.
  2. Weather Protection – To protect the building interior from weather elements.
  3. Insulation – To provide thermal insulation via insulation boards or batt insulation.
  4. Longevity – To perform for the expected service life.
  5. Aesthetics – To provide a desired, unblemished appearance.

Fenestration/Glazing Systems

Fenestrations are openings in a building’s façade and part of the building envelope. This includes windows, doors and skylights. Fenestrations can allow natural light to enter the building and provide a natural point of ventilation, air circulation and egress.

Curtain Wall

A curtain wall is a structural outer covering that protects a building from weather elements. They can act as both a buffer and an insulator and are typically made of aluminum and glass. Curtain wall systems are energy efficient and often provide interesting and sometimes elaborate design aesthetics to a structure.

Below-Grade Waterproofing

Below-grade waterproofing is the process of applying coatings and membranes to the walls of a building’s foundation below ground level. It is essential to create a water-tight barrier between the foundation of the building and the outside elements. Water can lead to the erosion of building materials over time and affect the overall structural integrity of a building and pose a life and safety issue to the occupants.

Download Our Free White Paper on Building Envelope Forensics

One of the most common issues that arise with the building envelope is water intrusion. However, it’s not always apparent how water has penetrated the building. Less noticeable signs may point to envelope failure, such as the presence of mold or stains on ceiling tiles or walls.

Download our white paper to learn more about common building envelope issues and how to diagnose them. Contact us today to set up a free building envelope consultation.

Improve the Performance, Safety and Efficiency of Your Building with Technical Assurance

The building envelope and its various components directly affect the longevity and energy efficiency of a building. With a systematic approach to quality assurance, our commissioning process improves the performance, safety and efficacy of a building and ensures that projects meet specific quality requirements as outlined by the owner. Contact us today to set up a free consultation!