What Exactly is a Building Envelope?

What is a building envelope? 

The “envelope” of a building is the exterior skin that acts as a barrier to the following:

1. water
2. water vapor
3. air
4. temperature

The purpose of the skin is to control or prevent the flow of air, water, and temperature between the exterior environment and the interior environment.   

What is it made of?

The envelope begins below the building and typically consists of a floor slab.  Below the floor slab there are generally plastic vapor barriers to keep moisture from migrating through the concrete and into the building.  Lack of a vapor barrier in a basement floor slab often results in a damp, musty odor, found in residential housing constructed with no vapor barriers. 

Above the floor slab are the foundation walls.  These walls also require protection from the outside environment.  Below-grade waterproofing membranes on the exterior of the foundation walls keep water and water vapor from entering the building.

The envelope becomes more complex above ground than below it, where drastic changes in temperature and weather occur.  In order to efficiently control the interior environment, the walls and roof contain all three basic elements of protection: 

1. vapor barriers to control the flow of water vapor,
2. insulation to contain heat and maintain temperatures, and
3. exterior siding, cladding, flashings, coatings, membranes, wall panels, or other “skin” to keep water out.

The latter is arguably the most critical part of the skin of a building.  Even the most basic of structures (primitive camp, straw hut, tipi) contain a roof and wall system designed to keep water out. 

Waterproofing systems

A waterproofing system is critical to the longevity and efficiency of the building structure.  Often times, waterproofing cannot be accessed once construction is complete without extensive demolition.  A very careful evaluation of options should occur prior to selecting the system that is best for your project needs.

There are many factors to consider when choosing the waterproofing components for your building.  Consider the following questions and criteria prior to making your selection:

1. Is the product recommended for use on your building’s substrates/materials?
2. Is the product suitable for the environment? What will it be exposed to?
3. Is there a comparison of the performance of various materials?
4. Will liquid applied or sheet applied products be easier to install?
5. Does the manufacturer have local distribution and support?
6. Is there a comparison of both material and installed costs of various systems.
7. Does the product have a strong track record?
8. Are the consultants and applicators experienced with the products?
9. Will the products be safe to use around building occupants?
10. Are there environmental limitations for applying the product?
11. Does the material supplier have installation drawings for typical construction details?
12. What are the terms of the manufacturer’s warranty?

There are many products and technologies available.  Developing a list of criteria and performance that must be met will help narrow your selection and assure an appropriate system is selected.

Want to know more about waterproofing products to keep water out of your building?  Check our interactive tool. Hover your mouse over the image to see how our products can solve your waterproofing needs.

https://chasecorp.com/construction-materials/building-envelope/building-envelope-interactive/