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Introduction to Insulating the Building Envelope in Connecticut and New York

Introduction to Insulating the Building Envelope in Connecticut and New York

The spaces in a building are enclosed by – created by – walls, floors, ceilings, and roofs. The enclosure is known as the building envelope. Insulation is the material that is installed in the walls, ceilings, floors, and roofs to slow the transfer of heat from the hot side to the cold side. In the winter, it’s heat that’s trying to leave a building; in the summer, it’s heat that’s trying to enter a building. Insulation is rated by its ability to resist this transfer and it’s known as R-value. The greater the R-value, the higher its resistance to heat transfer. In general, for buildings in New York (NY) and Connecticut (CT), more insulation is better because of the wide seasonal temperatures swings we endure in the northeast: 0º to 100º. Building owners benefit from higher insulation values through lower heating and air conditioning costs and greater comfort.

Types of Insulation For Building Envelope:

There are generally four types of insulation in use today in CT and NY: foamed-in-place such as spray polyurethane foam; fibrous such as fiberglass, cotton, and mineral wool; rigid such as polystyrene; and loose fill such as cellulose. R-value varies from approximately R-7 per inch of thickness for certain spray polyurethane foams to approximately R-3.5 per inch of thickness for fibrous types. Each one has certain advantages and the one you choose will depend on the specifics of your building project.


Vapor Barriers:


A vapor barrier keeps water vapor from penetrating the building envelope – from outdoors, it’s humidity, from indoors, it’s moisture from cooking, bathing and the like. The selection and placement of a vapor barrier depends on the type of insulation that is used and on the climate. In NY and CT, a separate vapor barrier, where needed, is installed between the conditioned space and the insulation, most typically, attached to the inside face of the framing directly behind the wallboard finish. Fibrous insulations generally require a vapor barrier and are manufactured either with or without an integral barrier. Closed-cell polyurethane insulation is its own vapor barrier, so a separate barrier is not required.


Ventilation and Indoor Air Quality:


We all need fresh air to live. Indoor air tends to get stale, especially in NY and CT in the summer and winter when we have the windows closed. Some sort of ventilation is required. Fibrous insulations are not air barriers and permit uncontrolled air infiltration, which we commonly experience as drafts around windows, doors, and electrical outlets. Closed-cell spray polyurethane insulation is an infiltration barrier and creates an extremely tight building envelope. This requires some sort of mechanical ventilation to allow for the controlled introduction of outside air.




The selection of the insulation best suited for your building’s envelope requires careful consideration. The Beacon Projects Group can assist you with evaluating these various insulation alternatives and arriving at a solution that meets your building needs.

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