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PROFITS: Special Report | By Achilles Karagiozis, Ph.D. The tight house Building science advancements, research and software developments help bring new solutions to the table to deliver durable, energy-efcient homes I n response to rising energy costs, a growing number of homeowners are turning to retrofit solutions to increase the performance, comfort and energy efficiency of their homes. As a result, remodeling professionals are seeing a spike in requests to help create tight, energy-efficient homes. Although great for business, these requests can present an incredibly challenging situation for remodelers. It often means working without having the benefit of knowing what building materials and applications were used in the original structure, or if control elements on an existing building envelope are functioning at their present state, or if they were properly installed. To help remove some of the educated guesswork, remodelers can leverage building science advancements as tools to help make air sealing, moisture management and overall energy efficiency easy and straightforward to achieve in retrofit applications. AIR SEALING Air infiltration has a direct correlation to a home's comfort, durability and energy efficiency. Air leakage accounts for between 25 to 40 percent of the energy used for heating and cooling in a typical residence, according to "Building Envelope Improvement: Air Sealing" by the U.S. Environmental Protection Agency, especially 30 December 2013 QR in colder climate zones. Across all climate zones, air intrusion is one of the most significant sources of moisture that can cause condensation and damage inside the walls of a home. Remodelers have the unique opportunity to address these issues by retrofitting from the inside to add air tightness to the structure and ultimately improve the energy efficiency and performance of the home. Yet, with the average home containing nearly a mile of joints, it can be very challenging to identify the most effective joists and the garage-tohouse common wall. For remodelers, this research reinforces the importance of properly insulating the attic in existing homes. Removing the existing insulation from the attic ceiling, then properly creating an air tightness plane at the ceiling followed by adding extra, new fiberglas insulation will enhance the thermal performance, improve air tightness and maximize the durability of the structure by reducing thermal bridging and preventing The most important areas for air-sealing efforts are the top plate-to-attic, recessed lights, duct boots, band/rim joists and the garage-to-house common wall. areas in the home to address air leakage and infiltration issues. To explore the complexity of air leakage, the Owens Corning Building Science Team conducted an extensive air infiltration research study that identified the specific exterior joints in a home where air is most likely to enter and escape through vulnerable gaps, cracks and seams. The study revealed that the five most important areas for builders to focus their air-sealing efforts and dollars are the top plate-to-attic, recessed lights, duct boots, band/rim ForResidentialPros.com moisture accumulation. The end result for homeowners is improved energy efficiency resulting in increased energy cost savings and comfort. MOISTURE MANAGEMENT Another key metric for overall building performance is preventing moisture infiltration. Moisture acts as a pollutant inside the home and can enter the structure from built-in stored moisture, vapor transport via diffusion and bulk water from absorption of driving rains. Rooted in the laws of physics, moisture management addresses air leakage, water movement, vapor diffusion and moisture accumulation to avoid the degradation of the thermal envelope and other potentially negative consequences. Controlling liquid and vapor moisture flow helps prevent the growth of unhealthy mold, the onset of corrosion, salt efflorescence and overall building failures. An extreme example of when moisture management goes wrong was illustrated in 1996 when more than 3,000 executive homes in the Wilmington, N.C., area had failures handling incidental water penetration that passed through exterior cladding causing toxic mold, materials deterioration and building failure. To avoid moisture-related failures, a good mantra to keep in mind is: insulate right, ventilate right and use the necessary control elements. It is recommended that control elements, including exterior cladding, weather-resistant barrier, fiberglass insulation and vapor control layers become fine-tuned for optimum performance. Every hour of the day, heat and moisture is released into the home from its occupants, animals and even plants, causing vapor diffusion back and forth