What is a Building Envelope?

A building envelope is the physical barrier between the conditioned (internal) and unconditioned (external) environment of a building. It includes the floors, walls, windows & doors, ceiling & roof.

The building envelope contains three main layers or barriers;

  1. Water Control Layer or Weather Barrier (WRB)
  2. Thermal Barrier or primary insulation layer
  3. Air Barrier (IAB)

Depending on the design, the location, materials specified and how well the building is built will determine how well your building envelope performs.

The building envelope plays a crucial role in a building’s energy efficiency. In winter, it helps prevent the transfer of heat from inside to outside (heat loss), and during summer it keeps the cool air inside (saving the occupant $) and reduces the heat coming through windows (heat gain).

Think of it like;

  • Weather barrier keeps the rain & wind out.
  • Thermal barrier keeps the heat in with bulk insulation and the heat out with reflective insulation.
  • Window shading & types of glass work with the thermal barrier.
  • Air barrier stops uncontrolled air movement which keeps the internal temperate comfortable by reducing warm air out or cold air in.

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