Glossary · Insulation & windows

Building envelope

Also called: building shell · thermal envelope · house envelope · building enclosure

Everything that separates inside from outside — foundation, walls, windows, doors and roof — and controls heat, air and moisture flow.

What it means

A good envelope has continuous insulation to slow heat, an air barrier to stop air leakage, and the right vapour control and drainage to manage moisture. Weak spots include the attic, rim joist, windows and anywhere pipes, wires or ducts pass through. Audits assess it with a blower door test, infrared (thermal) imaging and an insulation inspection.

Why it matters in an audit

Fixing the envelope first lowers heating and cooling needs, which can let you buy smaller, cheaper equipment, and some programs now require it before paying for a heat pump.

Sources

Learn more here

Related terms

Air barrier The continuous layer of materials in walls, ceilings and floors that stops air from leaking through the building envelope.
R-value How well a material resists heat flow; higher is better, and insulation is rated with it, such as R-20 for walls or R-50 for attics.
Air leakage Uncontrolled air moving in and out of a house through cracks and gaps, carrying heat, moisture and outdoor pollutants with it.
Vapour barrier / vapour retarder A layer that slows water vapour moving through walls and ceilings, to keep it from condensing inside the structure.
Thermal bridging Heat taking a shortcut through materials that insulate poorly, like wood studs, steel or concrete, running from the warm side to the cold side.
Continuous insulation (ci) A layer of insulation running unbroken over the framing, usually rigid boards on the outside of walls, to stop heat escaping through studs.

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