You might think it’s just a wall and a roof that keep you safe from that terrible weather outside. But the “building envelope” – defined as the part of a building that separates the interior environment from the exterior – includes many different components, each of which can be complex and multi-layered.
The four basic functions
Typical building envelope elements include walls, roofs, floors and ‘fenestrations’ (windows, doors, skylights and other openings). Each one can contain many different layers and materials. Take the example of a typical wall in a North American house. It could include a gypsum board, a vapour barrier, cavity insulation such as stone wool installed between wooden studs, an OSB board (Oriented Strand Board - made from resin-bonded wood flakes), a water-resistant barrier, exterior insulation and, finally, cladding. That’s a single part of the building envelope – but with seven different layers!
Whichever part of the interior it’s protecting, a building envelope has four basic functions:
- Support, transfer and accommodate structural loads imposed by the environment and the building
- Block and regulate heat, air, moisture and sounds between the exterior and interior
- Finish the surfaces to meet aesthetic or other performance requirements
- Distribute services and utilities such as electricity and water.
It’s interaction that matters
As well as doing all of this, building envelopes and their components must satisfy a huge range of qualities to do their job. Are they easy to build? Long-lasting? Easy to repair and maintain? Safe? Cost effective?
Overall, with a building envelope, it’s interaction that matters. All the components need to work together effectively to support a comfortable interior climate in environmental conditions that could change quickly from driving rain to hot sun to freezing cold. Stable, durable materials like stone wool are an essential part of the mix.