Generally speaking, a building envelope is the exterior shell of a given structure (i.e. exterior walls, roof, and floor). More specifically, a building envelope consists of the entire system of building materials and design elements that control the air movements, water vapor movement, and temperature of a given structure. Components like insulation, air barriers, and vapor barriers must work in concert to maintain a more consistent, more comfortable, and healthier interior environment. Numerous cutting-edge materials and construction practices are being utilized to extend the sustainability and service life of commercial and residential structures.Build Tight, Ventilate Right
Ventilating attics and crawl spaces has been the standard and code-required practice of residential design and homebuilding for decades. Despite that longevity, the practice of ventilating these areas was simply a result of traditional materials' inability to address radiant heat transfer, moisture condensation, and the results of "stack-effect issues."
The main issue with ventilating attics and crawlspaces is the free exchange of outside air with inside air. Outside air brings moisture, pollen, airborne particulates, pollution into the home, not to mention the introduction of insects, rodents, and other pests through the vent openings. The pleasant, clean, conditioned indoor air escapes, or is forced from the living space. Moreover, during summer and winter months, these spaces are filled with hot and frigid air.
Most heating and cooling utilities, and their associated ducts, are located in attics and/or crawlspaces, which can reduce the temperature of warm duct air (during the winter) or increase the temperature of cold duct air (during the summer) up to 10%, simply due to radiant heat transfer. Furthermore, moisture and mold can also form within the ducts under particular temperature conditions, potentially negatively impacting the health of occupants.
An especially problematic issue occurs during the summer, when heat from the sun radiates onto roof surfaces and then transfers into attic spaces via conduction. In some climates, attic temperatures can reach upwards of 150 degrees F (learn more about Urban Heat Islands). The excessive heat is eventually transferred into the living space, resulting in air conditioning units increasing both their workload and energy consumption. Additionally, the increase in temperature can contribute to the formation of condensation and potentially result in mold growth.
Cutting-edge building materials and modern building science techniques remain unfamiliar to builders and design professionals, who typically rely on often-outdated building codes for their projects. They will often argue the old adage that "a home needs to breathe," without acknowledging that a reliance on ventilated attics and crawlspaces, or a leaky living space for that matter, are not the only - or the optimal-construction methods. Indeed, the implementation of modern materials in the building envelope can produce a home that is tighter, more comfortable, healthier, and more energy efficient by reducing operational stress on the air conditioning system and controlling the flow of air in and out of a home.
SPF insulation is a far more versatile and more effective building material that either fiberglass batt or blown cellulose insulation. Spray foam benefits a home's operational performance, energy consumption, structural integrity, and air quality.