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Temperature cycling in aging apparatus
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Duct leakage is a major source of energy loss in residential buildings. Most duct leakage occurs at the connections to registers, plenums, or branches in the duct system. At each of these connections, a method of sealing the duct system is required. Typical sealing methods include tapes or mastics applied around the joints in the system. Field exam...
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... Retrofits need to be durable so that the benefits will still be in place 25 to 50 years from now. Examples of durability concerns include not using cloth duct tape (due to thermal degradation, see Walker and Sherman 2003), and avoiding moisture problems. This retrofit case study addressed the durability issue by having better equipment sizing for better humidity control, more ventilation (by adding an economizer) for better indoor IAQ and humidity control, and use of good duct sealants to prevent entry of humid outdoor air. ...
This case study focusing on a residence in northern California was undertaken as a demonstration of the potential of a systems approach to HVAC retrofits. The systems approach means that other retrofits that can affect the HVAC system are also considered. For example, added building envelope insulation reduces building loads so that smaller capacity HVAC system can be used. Secondly, we wanted to examine the practical issues and interactions with contractors and code officials required to accomplish the systems approach because it represents a departure from current practice. We identified problems in the processes of communication and installation of the retrofit that led to compromises in the final energy efficiency of the HVAC system. These issues must be overcome in order for HVAC retrofits to deliver the increased performance that they promise. The experience gained in this case study was used to optimize best practices guidelines for contractors (Walker 2003) that include building diagnostics and checklists as tools to assist in ensuring the energy efficiency of ''house as a system'' HVAC retrofits. The best practices guidelines proved to be an excellent tool for evaluating the eight existing homes in this study, and we received positive feedback from many potential users who reviewed and used them. In addition, we were able to substantially improve the energy efficiency of the retrofitted case study house by adding envelope insulation, a more efficient furnace and air conditioner, an economizer and by reducing duct leakage.
... Air leakage in ducts has been identified as a major source of energy loss in residential buildings. Thirty to forty percent of air flow leaks in and out of ducting systems in residential buildings, and most of the duct leakage occurs at the connections to registers, plenums or branches in the air distribution system (Walker and Sherman 2000). This study is a continuation of previous studies conducted at LBNL (Walker et al. 1998a and 1998b), whose objectives are to develop new test methods for duct sealant longevity, evaluate different sealant types (e.g., tape, mastic, aerosol), facilitate the development of consensus standards (e.g., ASTM), and technology transfer. ...
... A standard pressure of 25 Pa was chosen for leakage measurements of individual sealants because this is a typical pressure that would exist in the branches of a residential duct system (Walker and Sherman 2000). The flexible core-to-collar joint specimens underwent an initial six months period (starting in February 2002) of aging with visual inspection and leakage measurements once a month. ...
This paper addresses the effectiveness of using duct tape in sealing residential air distribution systems through two laboratory longevity tests. The first test involved the aging of common “core-to-collar joints” of flexible duct to sheet metal collars, and sheet metal “collar-to-plenum joints” exposed to continuous 200°F (93°C) circulating air. The second test consisted of baking duct tape specimens in a constant 212°F (100°C) oven following the UL 181BFX “Temperature Test” requirements. The study concluded that the duct tape performance in sealing joints depends on the joint's space dimensions; it gets worse as the number of dimensions required to describe the joint increases (1-D to 3-D). This is essentially caused by the shrinkage of the duct tape backing that results in the peeling of its rubber-based adhesive off the sheet metal fixture. The baking test results showed that the failure in the duct tape joints could be attributed to the combination type of the duct tape and the material it is applied to.
This report was prepared as a result of work sponsored by the California Energy Commission (Commission), through a contract with the Regents of the University of California, California Institute for Energy Efficiency (CIEE). It does not necessarily represent the views of the Commission, its employees, the State of California, The Regents, or CIEE. The Commission, the Regents, the State of California, CIEE, their employees, contractors, and subcontractors, make no warranty, express or implied, and assume no legal liability for the information in this report; nor does any party represent that the use of this information will not infringe upon privately owned rights. This report has not been approved or disapproved by the Commission or CIEE, nor has the Commission or CIEE passed upon the accuracy or adequacy of the information in this report.
In the mid-1990s, Lawrence Berkeley National Laboratory (LBNL) initiated a project to study the durability and longevity of duct sealants. Focus was on improving the test procedure and solving the problem of why duct tape could pass the UL 181B tests and not have sufficient longevity to be used in many field applications. Additional tests were thus conducted to understand the performance and durability of various duct sealing approaches. Results show that care must be taken when selecting duct sealants if long-term durability of the seal is to be maintained.
