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General Introduction
Published in Neha Gupta, Gopal Nath Tiwari, Photovoltaic Thermal Passive House System, 2022
This is an effective way to reduce the energy demand of a building because of the temperature difference between the inside and the outside, which can cause heat transmission. Each part of the building contributes to this heat flow depending on the size and thermal properties of the elements. The thermal transmittance, known as the U-value (refer to Section 2.8), is the most important thermal property of the building envelope. It gives an idea of how big the transmission loss per square meter is per degree temperature difference between indoors and outdoors.
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Published in Pablo La Roche, Carbon-Neutral Architectural Design, 2017
The heat flow through a building’s envelope always takes place from warmer surfaces to cooler surfaces and can be from exterior to interior or interior to exterior depending on the temperatures. Therefore, to determine the heat flow, the resistance of the different layers of the wall must be added to the surface resistance, or air-to-air resistance (Ra – a). The inverse value of the air-to-air resistance is called the thermal transmittance coefficient (U), and its unit is W/m2 °C (Figure 8.14). Thermal transmittance is the value that best defines the amount of heat that can be transmitted through a component of the building, and low U-values block more heat than high U-values. () Ra−a=Rsi+ΣRm+Rso
Introduction
Published in John Roberts, Alan Tovey, Anton Fried, Concrete Masonry Designer's Handbook, 2014
John Roberts, Alan Tovey, Anton Fried
The thermal transmittance (U-value) is the rate of heat flow through unit area of the element when a unit temperature difference exists between the air on each side. The U-value takes into account, as well as the resistance offered by the fabric, the outside and inside surface resistance. In simple terms thermal conductivity is the reciprocal of the sum of the resistance to the passage of heat.
An instructional design for building energy simulation e-learning: an interdisciplinary approach
Published in Journal of Building Performance Simulation, 2019
As the national regulation neglects the moisture sorption effects, the heat transfer through the opaque envelope is considered purely conductive, disregarding the phase change terms presented in moisture models (Advanced Level 3). In this case, the opaque envelope thermophysical properties are reduced to only three: the specific mass, the specific heat and the thermal conductivity. Those thermophysical properties are associated with concepts in the field of architecture known as thermal transmittance (or overall heat transfer coefficient in the heat transfer field) and thermal inertia (related to the product between specific heat and density), which are directly associated with the energy performance of opaque elements of the building envelope. Those concepts can be visualized quickly by the students as they appear on the left part of the building geometry and envelope on the BES CMap (Figure 4). In the building physics branch, students can see the governing differential equations for the opaque wall model.
Toward sustainable school building design: A case study in hot and humid climate
Published in Cogent Engineering, 2018
Thermal transmittance is an important aspect in building energy performance. Tsikaloudaki (2012) findings indicate that in hot and warm climate regions, higher solar transmittance could lead to worse energy pattern. In contrast, it might be more beneficial in cold regions or cooler periods during the year. Tsikaloudaki (2012) suggested that the thermal coefficient should not be lower than 2.0 W/m2K, However, all glazing area in school buildings in Saudi Arabia have a single clear glazing layer which is inefficient for reduction in heat exchange that take place in window system. Many types of materials which can be utilized in glazing system to enclose high energy performance, low-E glazed unit was found to be the most effective system (Cinzia, Linda, & Elisa, 2012; Msnuela, Anna, Salvatore, & Antonio, 2016; Nicola & Inger, 2016; Tavares, Gaspar, Martins, & Frontini, 2014). Seunghwan, Hakeun, Byung, Hyesim, and Donghyun (2013) has reported that the use of low-E glazed unit can acquire 15.2 to 19.9% in total energy consumption in South Korea, however, this relies on the specification of selected materials.
Energy policy towards nZEB: The Hellenic and Cypriot case
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Effrosyni Giama, Elli Kyriaki, Paris Fokaides, Agis M. Papadopoulos
The thermal transmittance, which is expressed by the heat transfer coefficient (U value) is the most important feature to characterize the thermal performance of building elements (Figures 3 and Figure 4). It actually expresses the rate of heat transfer through a structure, which can be a single material or a composite building element, divided by the temperature difference across that structure. It is,therefore, a crucial parameter to define how much heat is lost through a given thickness of a particular material, including the three major ways in which heat transfer occurs – conductivity, convection, and radiation (Bikas and Chastas, 2014; Giama et al. 2016).