Protect Wall and Ceiling Work through Forensics
April 2009Contractors, architects and building owner/developers are building or renovating, "faster, quicker, cheaper” to keep afloat during this economic downturn. This fast paced and lower compensated market has reduced the architectural details for some projects, leaving the specifics to the contractor. Building owner demands on architects and contractors include stepped-up technology and material introductions, pressure to lower costs and provide more energy savings, and the use of green building materials and technologies. With new technology and products come additional standards, application education and new installation techniques. The successful contractor in this economic climate must grasp new products along with the installation requirements and accompanying standards—a difficult feat for even the most competent contractor.
Forensic building science is a growing specialty available to help evaluate designs for both the contractor and architect. The building science specialist plays an even more important role in the outcome of the completed building in today’s marketplace. They provide expert consultation and oversight for building systems during construction, and they provide detailing for the contractor and suggestions to the architects, all while helping coordinate the whole building system throughout the build. Many states now require on-site testing, such as water testing of fenestrations during the building process. The building science experts provide the proper testing, as well as recommendations, if necessary, to ensure that building systems are effective and lasting. They often develop mockups to provide details for the contractor that may not be obvious from the original drawings.
The building science team sets contractor meetings and field observation visits to help define the expectations, requirements and rationale behind technical envelope design details learned in the initial building investigations. Through investigations of numerous failed buildings, BCRA—a company that provides technical services throughout the investigation, design, construction and performance verification phases to ensure a successful and acceptable building, has found that a large percentage of envelope deviations could have been foreseen and corrected at either the design phase or construction phase if the proper initial investigation, independent technical reviews and field audits had been implemented. Although building science has provided a high level of technical design for many years, only now is the industry beginning to rise to the challenge.
As an example, during recent design reviews we have encountered lack of detailing especially for air barrier systems. The U.S. Department of Energy estimates that uncontrolled air leakage can account for 30 percent or more of a building’s energy losses. A properly installed air barrier prevents the movement of air through a building as well as the loss of heat via convection, an important trait in the maintenance costs, comfort or livability of buildings. The designs of an air barrier can be as simple as utilizing the gypsum wallboard as the air barrier. Unfortunately, the contractor needs to clearly understand the designs and installations of this sort of air barrier. Unsealed wall-to-wall, ceiling-to-wall, and floor-to-ceiling junctions may lead to performance failure as an air barrier. It is critically important to include these details on the drawings to ensure that they are well understood by the contractor.
Another important energy effecter is the heat or thermal barrier, which will increase energy consumption dramatically if it is installed inappropriately. Minimizing all three modes of heat transfer (conduction, convection, radiation) will create an energy efficient building as well as provide occupant comfort—a key to occupant productivity and well-being. By taking steps to achieve air and thermal tightness, the building science group can help reduce energy use by upwards of 40 percent and create a comfortable environment for its occupants.
Hygrothermal modeling uses known weather history for any region worldwide to design the best envelope system. Specific characteristics of each building material can be investigated as a system to ensure a wall design will not have condensation or thermal bridging issues. In the end, durable, cost-effective solutions are realized without costly failures.
Thermal performance can be observed nondestructively using infrared thermography. The building science group, following ASTM C1060 standards, performs thermal building inspections, ensuring that proper thermal barriers have been adequately provided. In addition, infrared thermography provides a clear picture of any problem areas, creating a quick analysis for adjustment or repair.
Air Leakage Testing
An air leakage test is a means by which to determine problem areas of the building and verify that the continuous air barrier has been designed and constructed properly. The building science group will pressure-test the building using ASTM E1827, testing the leakage rate for the building envelope and locate major areas of air leakage using infrared thermography.
This test is intended to show problem areas during the building phase to help make adjustments as needed ensuring that the final building construction has produced an effective air barrier so that air infiltration and exfiltration are minimized.
Another important test is for water infiltration. These are especially important when evaluating the performance of the window installations. The building science group will water test the windows using ASTM E331, testing for proper installation to protect against water intrusion. Again, infrared thermography allows the building science group to locate areas of moisture that would not typically be observed, helping to pinpoint problem areas and providing corrective measures.
Recently at a multistory condominium construction site, a rain event flooded many of the units with water. It was obvious from the standing water that some of the units were affected, but unclear if many of the units without standing water had been damaged. With the use of infrared thermography, moisture mapping of all six floors was performed during a morning visit. The moisture mapping showed the construction crews exactly which walls in each unit were distressed, allowing accurate placement of drying equipment.
Additional monitoring of the building provided important information on the condition of the building materials, preventing further damage to the material and allowing effective repositioning of drying equipment as needed or wallboard removal. Further investigations during the monitoring allowed the building science group to pinpoint problem areas where water intrusions occurred, allowing modification of the building construction process. The information learned and presented to the contractor allowed the board-hanging crews to continue, and enabled key intrusion points to be corrected during the construction process, thus preventing future water intrusions and saving significant repair costs.
The use of infrared thermography surveys provides key information during the installation of interior water-sensitive materials such as gypsum wallboard. At many phases of construction, interior materials can be exposed to water, such as during rain events. An infrared scan of the area can allow mapping of what materials were exposed to the water and monitor the remediation steps to dry the affected material. The building science group may also incorporate aerial infrared thermography in its roofing surveys for quick and accurate moisture survey.
BCRA’s building science group says that ultimately, performance is evaluated upon completion of the building. However, to achieve real energy savings, a comfortable environment and reliable maintenance, a coordinated effort of the preliminary investigation, design, construction and final performance testing is required. To effectively control heat, air, and moisture leakage and remove the cost of fixing or maintaining a poorly performing building, the heat, air and moisture barriers must be paid close attention in design, evaluation and construction as well as performance verification of the completed product.
Scott Wood, senior building science consultant, is an expert building science thermographer. He has performed investigations on hundreds of buildings, showing defects as well as providing corrective recommendations. Wood has taught building science classes on the use of infrared thermography in building investigations nationwide and Canada since 2003. His involvement in the field of thermography includes key consultant/instructor for the Building Science Institute, where he has provided training for hundreds in Infrared Building Science Certification classes, director of building sciences for the International Association of Certified Thermographers, numerous clinics and workshops.
BCRA, headquartered in Tacoma, Wash., leads the industry in the design, construction administration and testing of building envelopes and has been offering these services for years.