Insulation, Air Sealing, and Ventilation

Air sealing means blocking small gaps where outside air leaks in and indoor air leaks out.

Air sealing the garage wall means sealing gaps and penetrations so garage air does not leak into the home.

Attic ventilation is the controlled airflow that moves fresh air into the attic and exhausts warm moist air out.

A baffle is a channel that keeps an air path open from soffit vents into the attic above the insulation.

Batt insulation is insulation that comes in pre-cut blankets or rolls, usually made of fiberglass or mineral wool, sized to fit between studs, joists, or rafters.

A blower door test uses a powerful fan mounted in a doorway to measure how much air leaks in and out of a home.

Blown insulation is loose-fill insulation that is blown into attics, walls, or floors using a machine.

The building envelope is the boundary between indoor comfort and outdoor weather, including walls, roof, floors, windows, doors, and the sealing around them.

Cellulose insulation is made from recycled paper treated with fire retardants, typically installed as blown-in loose fill.

Closed-cell foam is a dense type of spray foam insulation that acts as both insulation and a vapor barrier.

Continuous insulation is insulation that runs over framing without breaks, often on the exterior of the wall.

Dehumidification is removing moisture from the air.

Dew point is the temperature where air turns its moisture into liquid water on a surface.

An ERV brings fresh air in and pushes stale air out while saving some heat and moisture.

Fiberglass insulation is insulation made from fine glass fibers, available as batts, rolls, or loose-fill.

Humidity is the amount of water vapor in the air, often expressed as relative humidity.

IC-rated fixtures are recessed lights approved for direct contact with insulation without creating a fire hazard.

Low-E is a thin coating on glass that reflects heat. It helps control heat loss and heat gain.

MERV rating is a score for how well an HVAC filter captures particles.

Mineral wool insulation is made from rock or slag fibers. It is denser and more fire-resistant than fiberglass.

Open-cell foam is a softer type of spray foam insulation with lower density that allows vapor to move through it.

R-value measures how well insulation resists heat moving through it. Higher is better.

A ridge vent is a vent at the peak of the roof that lets hot air escape from the attic.

Rigid foam insulation is stiff foam boards used to add continuous insulation on the exterior of walls or under slabs.

A soffit vent is a vent under the roof overhang that lets fresh air enter the attic.

Spray foam insulation is a liquid that expands and hardens on contact, filling cavities and sealing air leaks at the same time.

Thermal bridging happens when heat slips through parts of an assembly that insulate poorly, like studs or metal.

A vapor retarder slows water vapor moving through a wall or ceiling.

Ventilation is the controlled exchange of indoor and outdoor air to maintain air quality.