The building sector accounts for approximately 40% of total global energy usage. Energy consumption for space heating and cooling makes up 60% of the total consumed energy in buildings. This paper presents a comprehensive technical review of passive wall systems in building envelopes while discussing their respective capabilities in optimizing energy efficiency. Different types of energy efficient walls such as Trombe Walls, Autoclaved Aerated Concrete Walls, Double Skin Walls, and Green Walls are explored. Furthermore, novel concepts for optimizing energy efficiency in building envelopes are also introduced. Finally the utilization of passive wall systems to save energy while improving the building environmental impacts is discussed.

Application of passive wall systems for improving the energy efficiency in buildings: A comprehensive review

Solving the matter of traditional energy consumption and finding the proper alternative resources are vital keys to a sustainable development policy. In recent years, many different thermal insulation materials have been developed for better energy efficiency and less environment damage. These products have confirmed their usefulness in buildings due to their benefits such as low density, high thermal resistance , and cost effectiveness. The efficiency of thermal insulation depends on their thermal conductivity and their ability to maintain their thermal characteristics over a period of time. This study presents factors influencing the thermal conductivity coefficient of three main groups including conventional, alternative, and new advanced materials. The most common factors are moisture content, temperature difference, and bulk density. Other factors are explained in some dependent studies such as airflow velocity , thickness, pressure, and material aging. The relationship between the thermal conductivity values with the mean temperature, moisture content, and density which were obtained from experimental investigation has also been summarized. Finally, uncertainty about the thermal conductivity value of some common insulation materials is also reviewed as the basis of selecting or designing the products used in building envelopes.

An overview of factors influencing thermal conductivity of building insulation materials

Building dynamic simulation tools, traditionally used to study the hygrothermal performance of new buildings during the preliminary design steps, have been recently adopted also in historical buildings, as a tool to investigate possible strategies for their conservation and the suitability of energy retrofit scenarios, according to the boundary conditions. However, designers often face with the lack of reliable thermophysical input data for various envelope components as well as with some intrinsic limitations in the simulation models, especially to describe the geometric features and peculiarities of the heritage buildings. This paper attempts to bridge this knowledge gap, providing critical factors and possible solutions to support hygrothermal simulations of historical buildings. The information collected in the present work could be used by researchers, specialists and policy-makers involved in the conservation of building's heritage, who need to address a detailed study of the hygrothermal performance of historical buildings thorugh dynamic simulation tools.

Dynamic thermal and hygrometric simulation of historical buildings: Critical factors and possible solutions

Experimental evaluation of an active solar thermoelectric radiant wall system

This article is devoted to a review of one of the most effective systems among passive heating systems - the Trombe Wall. The main objective of this study is to revise the current potential of the Trombe Wall for cold climates. This article discusses the main subspecies of the Trombe Wall. A qualitative assessment of the cold climatic conditions use possibility was given for each subspecies. There were analyzed the most interesting studies on each structural element of the Trombe Wall, the possibility of using the Trombe Wall in high-rise buildings. The Trombe Wall effect on the exterior of the whole building was evaluated. A brief technical and economic assessment of the Trombe Wall in cold climatic conditions was carried out to determine the economic potential in this work. Based on the results of the review, the main gaps and problems of the Trombe Wall in cold climatic conditions using were identified, and the most appropriate constructive solution for this was put forward. The main directions for future studies of the Trombe Wall were established such areas as improving the Trombe Wall thermal protection, the influence of the adjustable heat transfer coefficient on the Trombe Wall thermal efficiency, developing a mathematical model that takes into account the combined operation of the Trombe Wall with the central heating source of heat.

A review of the current work potential of a trombe wall

A numerical and experimental analysis of the air vent management and heat storage characteristics of a trombe wall

A model for the effective thermal conductivity of moist porous building materials based on fractal theory

Effect of moisture migration and phase change on effective thermal conductivity of porous building materials

Understanding the quantitative relationship between the effective thermal conductivity and the moisture content of a material is required to accurately calculate the envelope heat and mass transfer and, subsequently, the building energy consumption. We experimentally analyzed the pore size distributions and porosities of common building materials and the influence of the moisture content on the effective thermal conductivity of building materials. We determined the quantitative relationship between the effective thermal conductivity and moisture content of building materials. The results showed that a larger porosity led to a more significant effect of the moisture content on the effective thermal conductivity. When the volumetric moisture content reached 10 %, the thermal conductivities of foam concrete and aerated concrete increased by approximately 200 % and 100 %, respectively. The effective thermal conductivity increased rapidly in the low moisture content range and increased slowly in the high moisture content range. The effective thermal conductivity is related to the moisture content of the materials through an approximate power function. As the moisture content in the walls of a new building stabilizes, the effective thermal conductivity of normal concrete varies only slightly, whereas that of aerated concrete varies more significantly. The effective thermal conductivity of the material is proportional to the relative humidity of the environment. This trend is most noticeable when the wall material is aerated concrete.

Chao Ma

Papers

A numerical and experimental analysis of the air vent management and heat storage characteristics of a trombe wall

A model for the effective thermal conductivity of moist porous building materials based on fractal theory

Effect of moisture migration and phase change on effective thermal conductivity of porous building materials

Nonlinear Effect of Moisture Content on Effective Thermal Conductivity of Building Materials with Different Pore Size Distributions

Comprehensive correction of thermal conductivity of moist porous building materials with static moisture distribution and moisture transfer