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Energy Basics
Published in Stan Harbuck, Donna Harbuck, Residential Energy Auditing and Improvement, 2021
One final source of energy loss in heating systems comes from “distribution losses.” These losses typically are a result of leaks in the pipes or ducts (mass transport) and result from the lack of insulation around pipes or ducts (radiation, conduction, and convection losses). You can reduce leaks (the most significant source of distribution losses) by sealing them. Ducts and pipes can be insulated and a radiant barrier can be installed to reduce the losses from conduction, convection, and radiation. Another example of distribution losses occurs when the circulation of air or water flows by the heat exchanger too slowly. This kind of a misfit situation, caused by an inadequately sized blower fan or water circulation pump, results in less heat being extracted through the heat exchanger from the burner gases, which, in turn, sends more energy out the flue in the process.
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Published in Pablo La Roche, Carbon-Neutral Architectural Design, 2017
Density is related to conductivity (Figure 8.11); the materials with the highest densities usually have the highest conductivities. Air, the element with the lowest density and conductivity, is one of the best insulators and is also the cheapest; therefore, it is recommended as one of the layers of a multilayer building assembly, roof, floor, or wall. However, heat flow in these air spaces occurs in several forms: Heat reaches the wall of the air space by conduction and then is transmitted to the other wall by convection and radiation. These air spaces can be ventilated to reduce heat flow by convection, such as in a ventilated attic if the heat flow is downward, otherwise it increases heat flow. To reduce heat flow due to radiation, a reflective or radiant barrier should be installed.
Attic ventilation and radiant heat barriers in naturally ventilated galvanized metal-Roofed buildings
Published in Advances in Building Energy Research, 2022
Jefrey I. Kindangen, Octavianus H. Rogi, Pierre H. Gosal, Veronica A. Kumurur
Unlike conventional insulation, which only slows down heat absorption, radiant barrier insulation has the advantage that it not only blocks but also reflects heat back to its source. As a type of insulation, radiant barriers are less well-known than common insulation, yet they may be used in conjunction with one another. The use of an attic radiant barrier in combination with a favorable and readily accessible air flow for removing hot air from the attic area is recommended in tropical humid climates when air flow is conducive and readily available. On hot days in humid tropical climates, the surface temperature of metal roofs may reach 57 °C or more (Kindangen et al., 2019). The greater the temperature differential between the two sides of the radiant barrier material, the more advantages it may be able to deliver to the building occupants. The sensible heat transfer between the human body and space is primarily a radiant transfer from the standpoint of thermal comfort (Atmaca et al. (2007)). The radiative qualities of clothing, walls, and other surrounds play a big role in heat transfer between humans and their surroundings (Xu and Raman (2021)). In this case, it is possible to employ radiant heat barriers, which are constructed on the bottom of the roof to restrict the heat from the zinc roof from escaping into the attic. In order to do this, while building a radiant barrier, it is important to pay close attention to the positioning of the barrier since dust accumulation on its reflective surfaces will reduce the reflecting capacity (Rish and Roux (1987), Fairey and Swami (2010), Miranville et al. (2008)).