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"An educated consumer is our best customer.”  – Sy Syms, CEO of the Syms Corporation 


Air barrier: Insulation that reduces the air movement through the building envelope. Notable deficiencies in the air barrier of the buildings account for over half of the heating energy lost to the outdoors.


Building envelope: The outer shell of the building that separates inside from outside. It includes things like the foundation, roof, exterior walls, attached porch, attached garage, exterior doors and windows.


Building science: The set of fundamental scientific principles, taken from several branches of science, that govern home performance.


Conditioned space: The areas of a building that are heated and cooled. 

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Fiberglass batt insulation: Fiberglass/mineral wool held together with adhesive. Works by trapping air in small pockets. If air is moving freely through the insulation, the insulation’s performance will be greatly diminished.


Home performance: The systematic approach to improving the comfort, health, safety, energy efficiency, and durability of a house. Home performance is governed by scientific principles involving physics, chemistry, and thermodynamics, and the interacting relationships between home components.


Loose-fill/blown insulation: Fiberglass/mineral wool or cellulose installed at low density to slow down air conduction. Serves only as a thermal barrier. Efforts to create an air barrier must be undertaken separately.


Off-gassing: When new, manufactured items release chemicals, also known as volatile organic compounds (VOCs), into indoor air.


R-Value: A measure of a material’s thermal resistance, which means how well a material resists heat transfer. Spray foam R-value is much higher than any other insulation type. However, even more important than R-value is the air barrier which most other commonly used insulations do not provide.


Stack effect: An occurrence in which warm air inside a house rises up and escapes out through holes in the building envelope, and is replaced by an equal amount of cooler air from outside that enters at the bottom.

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Spray foam: There are two types of spray foam. Per International Building Code, both types require a thermal barrier (ie: drywall) is applied between the foam and interior space.

  • High-density (closed-cell) SPF. Adheres well, is very durable, and resists moisture. Two pound density. Heat Keepers installs this type of foam.

  • Low-density (open-cell) SPF. Half pound density. Not as resistant to heat transfer as high-density..


Thermal barrier: Insulation that slows the conduction of heat energy from the warm inside to the colder outer.


Thermal boundary: The area between conditioned and unconditioned spaces. This is where insulation should be located and improved, if necessary.


Unconditioned space: The areas of a building that are not heated or cooled such as the attic, basement, or crawlspace. May or may not be within the building envelope.

* For more information about building and insulating terminology, visit the Building Performance Institute, Inc.


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