What is a Building Envelope or Building Enclosure?

Think of your building envelope as everything that separates the outside from the inside. When considering your outside walls, then, it’s the siding, the house wrap, the sheeting, the insulation, and the framing. These layers are designed to provide a barrier between living space and non-living space, so that heated or cooled spaces feel the way they’re meant to feel. 

A more technical definition of a building envelope (also known as a building enclosure) is the physical barrier between the interior and exterior of a building. It includes all the elements that separate the conditioned (heated or cooled) spaces inside from the unconditioned outside environment. 

The components of a building envelope are everything from the foundation to the shingles, but each plays a unique role in its function and role in enclosing the space. Each component (the roof, exterior walls, windows and doors, foundation or slab, insulation and air/vapor barriers) serves an essential function of building performance, contributing (or taking away from) your space’s energy use.  

Primary Functions of a Building Envelope: 

A well-designed building envelope increases energy efficiency, improves comfort, and extends the life of the building, while poor envelope design leads to issues like mold, high energy bills, and drafts. 

Thermal (Temperature) Control: Your space is able to maintain the temperature you intend for it to the degree that your building enclosure (or building envelope) is doing its job. A well-engineered building envelope keeps the cold outside in the winter and the cold inside in the summer.  

Moisture control: Particularly when looking at the vapor or moisture barrier, a building enclosure stops mildew and mold from growing in your space. If you’ve ever seen a bath fan vented directly into an attic (and not out the roof), you’ve seen mold growing. This is because moisture is being pushed directly into the attic. Moisture control both prevents water from coming in and manages vapors and moisture flow so that it properly and efficiently leaves the treated space. 

Air control: Part of engineering a building enclosure is making sure that air doesn’t flow where it’s not meant to flow and that it does flow where it’s meant to. Proper ventilation, air-tightness, and breathability are all essential factors of building enclosure design and engineering. 

Structural support: Some solutions in building envelope engineering provide significant structural support. Closed-cell foam insulation, for instance, brings noticeable stability and structural integrity. 

Noise control: Sufficient insulation as well as quality windows and doors are significantly impactful for noise reduction for spaces. Some geographic or metropolitan spaces require noise reducing efforts (such as near major airports or freeways). Some building owners simply prefer it. Regardless, your building envelope can perform for you in reducing external noise infiltration.