Breaking Old Rules for Air-Barrier Installation
In heating climates—areas where there is a significant need for heating—you may have noticed how the upstairs is often warmer than the down stairs if the ventilation is not balanced. Or it is warmer at the ceiling than at the floor. As the warm air rises, it creates a positive pressure at the top of the building and a negative pressure below. These pressure differences force warm air out through the top of the building, sucking cooler air into the lower section of the building. This is called the stack effect.
The stack effect and air leakage adds to the amount of air the HVAC system needs to cool or heat, and will also bring in outside pollutants and moisture.
CASE STUDY: ELEVEN55 RIPLEY
Photo courtesy of VaproShield
A water-resistive, vapor-permeable air-barrier sheet membrane served as an in-process replacement on the Eleven55 Ripley apartment complex in Silver Springs, Maryland, after the original fluid-applied air barrier failed to withstand the cold weather.
Photo courtesy of VaproShield
The WRB/air barrier selected for the building requires no primer and can be applied in wet or cold conditions.
More than 60,000 square feet of self-adhering, water-resistant, vapor-permeable air-barrier sheet membrane was applied to the Eleven55 Ripley apartment complex in Silver Springs, Maryland, as an in-process replacement for a failing fluid-applied air barrier that was unable to withstand the area’s cold temperatures and rainy weather.
After a particularly windy night during construction, the installation crew arrived to find the original air barrier torn and damaged. The team decided to replace the failing fluid-applied barrier with a self-adhered WRB/air barrier. They require no primers, and some can be installed in temperatures as low as 20 degrees Fahrenheit.
Image courtesy of VaproShield
The key to an efficient, healthy, and durable building is to control airflow, which brings in vapor, and stop heat flow.
To be most effective, the thermal (insulation) barrier, air barrier, and moisture barrier (liquid and vapor water) should be continuous all around the building exterior, including all rough openings, such as windows. The key, says building science consultant Scott Wood, “is to control air flow (which brings in the vapor), and stop convective heat flow.”
Stopping airflow and liquid water from entering a building envelope, yet allowing vapor to come and go, are the sophisticated functions we ask of our modern building envelopes. Let’s see how we got here.
CASE STUDY: FEDERAL CENTER SOUTH BUILDING
Photo courtesy of Benjamin Benschneider
A self-adhered, water-resistant, vapor-permeable air-barrier membrane was used in the reconstruction of the Federal Center South Building in Seattle, Washington.
Approximately 40,000 square feet of self-adhered, water-resistant, vapor-permeable air-barrier membrane was used on the reconstruction of the Federal Center South Building 1202 in Seattle, Washington. The 209,000-square-foot building serves as regional headquarters for the U.S. Army Corps of Engineers (USACE) Northwest District. The self-adhered WRB/air-barrier membrane helped the reconstruction project achieve a level of energy efficiency at the top 1 percent of all U.S. buildings, functioning as a continuous air-barrier membrane system, while protecting the structure from the damaging effects of moisture.
Despite a slim $65 million budget, Building 1202 “achieved the most innovative and high performance design in federal government building projects,” according to the American Institute of Architects.
Awarded one of AIA’s Top 10 Green Projects 2013 and a National Design-Build Award from Design-Build Institute of America, Building 1202 utilized a host of energy-saving and sustainable products to achieve a high-performance, long-lasting structure.
The design-build team has 0.5 percent of the original contract value at risk, pending verification of the building’s energy performance after one year of occupancy. This risk is shared between Sellen Construction, ZGF Architects, and the major subcontractors and design consultants who have primary responsibility for Building 1202’s energy performance.
Photo courtesy of VaproShield
When a brewery was founded in St. Paul, Minnesota, in the mid 1800s, little thought was given to air or vapor intrusion. Buildings were drafty, and energy was cheap. But when the brewery was converted to artists’ lofts in 2013, the buildings were brought up to today’s standards with a technologically advanced self-adhered WRB/air barrier.
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