Decreasing of Thermal Losses of the Light-Weight Building Envelope

2015 ◽  
Vol 729 ◽  
pp. 224-227 ◽  
Author(s):  
Tatyana Zhilina
Keyword(s):  
Heat Flow ◽  
Thermal Action ◽  
Building Envelope ◽  
Light Weight

Method of active thermal action on zone of thermo-conductive inclusions by use of direct heat flow has been discussed.

scholarly journals A new method to estimate point thermal transmittance based on combined two-dimensional heat flow calculation

2020 ◽  
Vol 172 ◽  
pp. 08005
Author(s):  
Jaanus Hallik ◽  
Targo Kalamees
Keyword(s):  
Heat Flow ◽  
Three Dimensional ◽  
Multiple Linear Regression Model ◽  
Building Envelope ◽  
New Method ◽  
Two Dimensional ◽  
Thermal Transmittance ◽  
Thermal Bridge ◽  
Thermal Bridges ◽  
Third Dimension

A well-insulated, airtight and thermal bridge free building envelope is a key factor for nearly zero energy buildings (nZEB). However, increased insulation thickness and minimized air leakages increase the effect of thermal bridges on overall energy efficiency of the nZEBs. Although several more prominent linear thermal bridges are accounted for in the practice the three-dimensional heat flow through vast array of fixation elements, mounting brackets and other point thermal bridges are usually neglected due to time-consuming model preparation routine, lack of input data as well as high number of different thermal bridges that have to be assessed for a single project. In this study a new method was proposed for predicting three-dimensional heat flow and the point thermal transmittance of thermal bridges caused by full or partial penetration of the building envelope with metal elements with uniform geometry in third dimension based on multiple two-dimensional numerical heat flow calculations. A new parameter (equivalent length of thermal bridge) was defined which incorporates the effect of additional thermal transmittance in third dimension when multiplied by the difference of two thermal coupling coefficients derived for two-dimensional cross section. Multiple linear regression model was fitted on database with 102 cases and verified with separate case of window to wall connection incorporating metal penetration at fixation points. The proposed methodology can be useful in general practice where the design team lacks the skills or software tools for conducting detailed numerical analysis in three dimensions.

Possible Solutions for Ground Slabs of Energy Efficient Buildings

2014 ◽  
Vol 1041 ◽  
pp. 105-108
Author(s):  
Anna Sedláková ◽  
Pavol Majdlen ◽  
Ladislav Ťažký
Keyword(s):  
Energy Efficiency ◽  
Heat Flow ◽  
Thermal Comfort ◽  
Energy Efficient ◽  
Direct Contact ◽  
Thermal State ◽  
Building Envelope ◽  
Heat Losses ◽  
Internal Environment ◽  
Energy Efficient Buildings

The building envelope is a barrier that separates the internal environment from the effects of weather. This barrier ought to facilitate the optimal comfort of the interior environment in winter as well as summer. It has been shown in practice that most building defects occur within the building envelope. This includes external walls, roofs and floors too, and is impartial to new or renovated buildings. Heat losses of buildings through external constructions – roof, external walls, ground slabs are not negligible. It is therefore important to pay more attention to these construction elements. Basementless buildings situated on the ground are in direct contact with the subgrade and its thermal state. An amount of heat primarily destined for the creation of thermal comfort in the interior escapes from the baseplate to the cooler subgrade. The outgoing heat represents heat losses, which unfavourably affect the overall energy efficiency of the building. The heat losses represent approximately 15 to 20 % of the overall heat losses of the building. This number is a clear antecedent for the need to isolate and minimalize heat flow from the building to the subgrade.

Application of Double-Sided Heat Flow Meter in Testing of Overall Heat Transfer Coefficient of Building Envelope

2013 ◽  
Vol 353-356 ◽  
pp. 2872-2876
Author(s):  
Hai Rong Dong ◽  
Shao Ming Qi
Keyword(s):  
Heat Flow ◽  
Thermal Property ◽  
Transfer Coefficient ◽  
Energy Saving ◽  
Field Testing ◽  
Building Envelope ◽  
Existing Buildings ◽  
Flow Meter ◽  
Thermal Transfer ◽  
Heat Flow Meter

It is essential to find out the thermal property of building envelope in order to design economical and reasonable scheme of energy-saving reconstruction. Field testing is a method of receiving the thermal property of envelope when existing buildings are reconstructed. In this paper, we focus on the need for obtaining the thermal transfer coefficient. A methoddouble-sided heat flow meter was introduced and used to test the thermal property of wall. The testing results show that it provides a feasible method for colleting basal data of energy-saving reconstruction of existing buildings.

Evaluation on CO2 Emission of Light Weight Steel Housing in Taiwan

2013 ◽  
Vol 284-287 ◽  
pp. 1325-1329 ◽  
Author(s):  
Yu Sheng Chang ◽  
Kuei Peng Lee ◽  
Wen Sheng Ou
Keyword(s):  
Energy Consumption ◽  
Co2 Emission ◽  
Building Materials ◽  
Green Building ◽  
Building Envelope ◽  
Light Weight ◽  
Steel Buildings ◽  
Rc Buildings ◽  
The Government ◽  
Building Policy

The reinforced concrete (RC) buildings commonly used in Taiwan not only create great pollutions in material manufacturing and construction phases but also destroy the environment. On the other hand, the light weight steel buildings are safe, healthy, comfortable, producing less waste, and environmental friendly. Therefore, light weight steel buildings have been promoted in Taiwan by the government as an important “green building” policy. In Taiwan, there is still a large market of low rise light weight steel housing. To promote light weight steel housing in Taiwan, we should evaluate its influence on environment. In this research, we established a CO2 emission database for light weight steel building materials and calculated CO2 emission for a light weight steel house. The results showed that a low rise light weight steel house has 39% less CO2 emission than an RC house in the same scale. A light weight steel house has a good building envelope that decreases energy consumption of air-condition by 35.42-42.95%. Therefore, a light weight steel house has less CO2 emission from building materials and energy consumption than an RC house.

Fly Ash Autoclaved Aerated Concrete Field Detection Analysis of Heat Transfer Coefficient of Self Thermal Insulation Building Envelope

2014 ◽  
Vol 631-632 ◽  
pp. 585-589
Author(s):  
Li Bai ◽  
Meng Niu ◽  
Ying Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Fly Ash ◽  
Heat Flow ◽  
Transfer Coefficient ◽  
Building Envelope ◽  
Aerated Concrete ◽  
Temperature Controlled ◽  
The Heat Transfer Coefficient ◽  
Heat Flow Meter

This paper mainly analyzes the principle and application conditions of temperature controlled tank-heat flow meter method in field testing the heat transfer coefficient. And according to the actual engineering examples, using temperature controlled tank-heat flow meter method to test the heat transfer coefficient of fly ash autoclaved aerated concrete building envelope. Analyzing and studying the testing data, design value and theoretical calculating value.

scholarly journals ALTERNATIVE METHOD FOR ON SITE EVALUATION OF THERMAL TRANSMITTANCE

2017 ◽  
Vol 15 (2) ◽  
pp. 341 ◽  
Author(s):  
Aleksandar Janković ◽  
Biljana Antunović ◽  
Ljubiša Preradović
Keyword(s):  
Heat Flow ◽  
Thermal Characteristics ◽  
Building Envelope ◽  
Heat Losses ◽  
Flow Meter ◽  
Simple Method ◽  
Building Element ◽  
Thermal Transmittance ◽  
Heat Flow Meter

Thermal transmittance or U-value is an indicator of the building envelope thermal properties and a key parameter for evaluation of heat losses through the building elements due to heat transmission. It can be determined by calculation based on thermal characteristics of the building element layers. However, this value does not take into account the effects of irregularities and degradation of certain elements of the envelope caused by aging, which may lead to errors in calculation of the heat losses. An effective and simple method for determination of thermal transmittance is in situ measurement, which is governed by the ISO 9869-1:2014 that defines heat flow meter method. This relatively expensive method leaves marks and damages surface of the building element. Furthermore, the final result is not always reliable, in particular when the building element is light or when the weather conditions are not suitable. In order to avoid the above mentioned problems and to estimate the real thermal transmittance value an alternative experimental method, here referred as the natural convection and radiation method, is proposed in this paper. For determination of thermal transmittance, this method requires only temperatures of inside and outside air, as well as the inner wall surface temperature. A detailed statistical analysis, performed by the software package SPSS ver. 20, shows several more advantages of this method comparing to the standard heat flow meter one, besides economic and non-destructive benefits.

scholarly journals Defining patterns of heat transfer through the fire-protected fabric to wood

2021 ◽  
Vol 6 (10 (114)) ◽  
pp. 49-56
Author(s):  
Yuriy Tsapko ◽  
Аleksii Tsapko ◽  
Olga Bondarenko
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Heated Surface ◽  
Fire Retardant ◽  
Thermal Action ◽  
Insulating Layer ◽  
A Value ◽  
Flow Through ◽  
Insulating Properties ◽  
Protective Screen

Under the thermal action on wood when applying a protective screen made from fire-retardant fabric, the process of temperature transfer is natural. It has been proven that depending on the thermal properties of the coating of fire-proof fabric, this could lead to varying degrees of heat transfer. Therefore, it becomes necessary to study the conditions for establishing low thermal conductivity and establishing a mechanism that inhibits heat transfer to wood. Given this, a mathematical model has been built of the process of heat transfer to wood when it is protected by a screen made of fire-proof fabric. According to the experimental data on determining the temperature on the non-heated surface of the fabric and the resulting dependences, the density of the heat flow transmitted to wood through fire-proof fabric was determined. Thus, with an increase in the temperature, the density of the heat flow to the surface of the wood through a protective screen made of fire-proof protected coating based on "Firewall-Attic" increases to a value above 16 kW/m2, which is not sufficient for ignition of wood. Instead, the density of the heat flow through the protective screen of fire-proof fabric protected by the "Firewall-Wood"-based coating did not exceed 14 kW/m2. This makes it possible to argue about the compliance of the detected mechanism of formation of heat-insulating properties in the protection of wood and the practical attractiveness of the proposed technological solutions. Thus, the peculiarities of inhibition of the process of heat transfer to wood through a protective screen made of fire-proof fabric under the action of a radiation panel imply the formation of a heat-insulating layer of coked cellular material when decomposing the coating. Thus, on the surface of the fire-proof fabric, a temperature above 280 °C was achieved and, on an untreated surface of the fabric, it did not exceed 220 °C, which is insufficient for the ignition of wood.

Shallow Water Heat Flow Measurements in Bras D'or Lake, Nova Scotia

1971 ◽  
Vol 8 (1) ◽  
pp. 96-101 ◽  
Author(s):  
Douglas S. Rankin ◽  
Roy D. Hyndman
Keyword(s):  
Heat Flux ◽  
Nova Scotia ◽  
Heat Flow ◽  
Surface Temperature ◽  
Shallow Water ◽  
Thermal Gradient ◽  
Light Weight ◽  
Flow Measurements ◽  
Made In ◽  
Conductivity Contrast

A light-weight oceanic thermal gradient probe was used for heat flow studies in Bras d'Or Lake, Nova Scotia. The measurements were made in St. Andrew's Channel, an elongated trough 270 m deep and 540 m wide. The heat flux of 1.50 μcal/cm2 s (63 mW/m2) is corrected for sedimentation, conductivity contrast, topography, and surface temperature differences.

scholarly journals Heat Transport Analysis in Rectangular Shields Using the Laplace and Poisson Equations

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1714
Author(s):  
Stefan Owczarek ◽  
Mariusz Owczarek
Keyword(s):  
Temperature Field ◽  
Steady State ◽  
Heat Flow ◽  
Direct Method ◽  
Transient State ◽  
Building Envelope ◽  
Heat Fluxes ◽  
Flow Process ◽  
Infinite Power ◽  
Building Physics

In the design of a building envelope, there is the issue of heat flow through the partitions. In the heat flow process, we distinguish steady and dynamic states in which heat fluxes need to be obtained as part of building physics calculations. This article describes the issue of determining the size of those heat fluxes. The search for the temperature field in a two-dimensional problem is common in building physics and heat exchange in general. Both numerical and analytical methods can be used to obtain a solution. Two methods were dealt with, the first of which was used to obtain the solution in the steady state and the other in the transient. In the steady state a method of initial functions, the basics of which were given by W.Z. Vlasov and A.Y. Lur’e was adopted. Originally MIF was used for analysis of the loads of a flat elastic medium. Since then it was used for solving concrete beams, plates and composite materials problems. Polynomial half-reverse solutions are used in the theory of a continuous medium. Here solutions were obtained by the direct method. As a result, polynomial forms of the considered temperature field were obtained. A Cartesian coordinate system and rectangular shape of the plate were assumed. The problem is governed by the Laplace equation in the steady state and Poisson in the transient state. Boundary conditions in the form of temperature (τ(x), t(y)) or/and flux (p(x), q(y)) can be provided. In the steady state the solution T(x, y) was assumed in the form of an infinite power series developed in relation to the variable y with coefficients Cn depending on x. The assumed solution was substituted into the Fourier equation and after expanding into the Taylor series the boundary condition for y = 0 and y = h was taken into account. From this condition the coefficient Cn can be calculated and, therefore, a closed solution for the temperature field in the plate.

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