24362 Blood River Road,
Springfield, LA  70462
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Office:  225-698-6309
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16881 Kinchen Road,
Livingston, LA  70754
How Spray Foam Helps the Buildings Envelope

The building envelope (or building enclosure) is the physical separator between the interior and the exterior environments of a building.  It serves as the outer shell to help maintain the indoor environment (together with the mechanical conditioning systems) and facilitate its climate control.  Building envelope design is a specialized area of architectural and engineering practice that draws from all areas of building science and indoor climate control.  A building's insulation, air barrier and vapor barrier all need to work together to achieve a more stable, comfortable and healthier indoor environment.

Ventilation of the attic and crawl spaces has long been the traditional code required for building homes.  This was required because standard materials and building design practices were not capable of addressing radiant heat transfer, condensation, and the results of stack-effect issues. 

The Stack effect or chimney effect is the movement of air into and out of buildings, chimneys, flue gas stacks, or other containers due to buoyancy.  Buoyancy occurs due to a difference in indoor-to-outdoor air density resulting from temperature and moisture differences. The greater the thermal difference and the height of the structure, the greater the buoyancy force, and thus the stack effect. The stack effect helps drive natural ventilation and infiltration.

In order to address heat transfer from weather issues, utilities, and the formation of moisture due to condensation and air infiltration, the only option was to ventilate the attics and crawl spaces. The major problem with ventilating these spaces is that the air brings moisture, pollution and other adverse problems and challenges with it. Furthermore, the vents to allow it in create voids in the building for insects and rodents to enter, and all our nice conditioned air that escapes, or is pulled from the living spaces to exit.
In fact, in the summer, the incoming air needs power consuming fans to bring it in, and it will never get any cooler than the outside air temperature. Why would we want 95 degree hot, humid, potentially pollution ridden air into our attic and crawl space? In the winter this air is freezing cold.

If our heating/cooling utilities and ducts are located in the attic and/or crawl spaces (most usually are) then their radiant contact with the ducts will cause up to 10% loss or more of the hot or cold air flowing through them due to radiant transfer.  Worse yet, moisture and mold can also form within the ducts during certain temperature conditions, causing adverse health effects to the building occupants or your family.
Another major reason that traditional methods call for attic ventilation is that during the hot summer months, heat from the sun builds on the roof and radiates into the attic space. In fact, it can build to upwards of 130 to 150 degrees or more.  This extreme heat radiates into the attic and the living space causing condensation and the potential for mold. Our air conditioning systems also need to work harder and consume more energy with all this heat directly above our heads. The extreme heat also makes it very uncomfortable to enter these spaces.
Most builders and design professionals are not familiar with modern materials and progressive building science techniques that can virtually eliminate all of these problems that force the traditional, less effective requirement for ventilation in these building spaces.

Builders and design professionals will also make the argument that your home needs to breathe. Well, they are absolutely correct. But why rely on cracks, gaps and holes in your building for passive ventilation, when you can build your home tight, healthy and energy efficient, and let the mechanical ventilation systems due the job properly.

Spray foam insulation can still provide benefits far greater than traditional materials such as fiberglass and cellulose, regardless of whether you decide to ventilate these spaces or not. By using spray polyurethane foam insulation you can increase your home's energy performance, structural integrity and air quality.
Photo Courtesy of Department of Energy - Energy Wise