Contents Preface.. VII 0Introduction1 0.1 Subject of the Book 1 0.2 Building Physics.. 1 0.2.1 Definition .. 1 0.2.2 Criteria 2 0.2.2.1 Comfort 2 0.2.2.2 Health 2 0.2.2.3..Architectural and Material Facts 3 0.2.2.4 Economy.. 3 0.2.2.5 Environment 3 0.3 Importance of Building Physics 3 0.4 History of Building Physics .. 4 0.5 References . 6 0.6 Units and Symbols 6 1 Heat Transfer .. 11 1.1 Overview.. 11 1.2 Conduction 13 1.2.1 Conservation of Energy 13 1.2.2 Fourier's Laws .14 1.2.2.1 First Law. .14 1.2.2.2 Second Law 15 1.2.3 Steady State 16 1.2.3.1 What Is It?. 16 1.2.3.2 One Dimension: Flat Walls .. 16 1.2.3.3 Two Dimensions: Cylinder Symmetry24 1.2.3.4 Two and Three Dimensions: Thermal Bridges..25 1.2.4 Transient Regime 30 1.2.4.1 What is Transient? 30 1.2.4.2 Flat Walls, Periodic Boundary Conditions31 1.2.4.3 Flat Walls, Transient Boundary Conditions43 1.2.4.4 Two and Three Dimensions ..47 1.3 Convection 48 1.3.1 Overview.48 1.3.1.1 Heat Transfer at a Surface ..48 1.3.1.2 Convection 49 1.3.2 Convection Typology .. 50 1.3.2.1 Driving Forces .. 51 1.3.2.2 Type of flow 51 1.3.3 Calculating the Convective Surface Film Coefficient . 51 1.3.3.1 Analytically 51 1.3.3.2 Numerically 52 1.3.3.3 Dimensional Analysis. . 52 1.3.4 Values for the Convective Surface Film Coefficient .. 54 1.3.4.1 Walls. 54 1.3.4.2 Cavities.. 56 1.3.4.3 Pipes 58 1.4 Radiation.. 59 1.4.1 Overview. . 59 1.4.1.1 Thermal Radiation 59 1.4.1.2 Quantities . 59 1.4.1.3 Reflection, Absorption and Transmission. 59 1.4.1.4 Radiant Surfaces. 62 1.4.2 Black Bodies. .. 62 1.4.2.1 Characteristics. .. 62 1.4.2.2 Radiation Exchange Between Two Black Bodies: The Angle Factor 65 1.4.2.3 Properties of Angle Factors .. 66 1.4.2.4 Calculating Angle Factors .. 67 1.4.3 Grey Bodies 69 1.4.3.1 Characteristics. .. 69 1.4.3.2 Radiation Exchange Between Grey Bodies 70 1.4.4 Colored Bodies .. 72 1.4.5 Practical Formulae 72 1.5 Applications 74 1.5.1 Surface Film Coefficients and Reference Temperatures 74 1.5.1.1 Overview.. 74 1.5.1.2 Inside Environment. .. 74 1.5.1.3 Outside Environment .. 78 1.5.2 Steady-state, One-dimension: Flat Walls 81 1.5.2.1 Thermal Transmittance and Interface Temperatures .. 81 1.5.2.2 Thermal Resistance of a Non-ventilated Infinite Cavity 85 1.5.2.3 Solar Transmittance .. 86 1.5.3 Steady State, Cylindrical Coordinates: Pipes .. 89 1.5.4 Steady-state, Two and Three Dimensions: Thermal Bridges. 90 1.5.4.1 Calculation by the Control Volume Method (CVM) .. 90 1.5.4.2 Thermal Bridges in Practice .. 91 1.5.5 Transient, Periodic: Flat Walls 94 1.5.6 Heat Balances .. 95 1.6 Problems.. 96 1.7 References109 2 Mass Transfer. 111 2.1 In General 111 2.1.1 Quantities and Definitions .. 111 2.1.2 Saturation Degree Scale 113 2.1.3 Air and Moisture Transfer .. 115 2.1.4 Moisture Sources 117 2.1.5 Air, Moisture and Durability 117 2.1.6 Linkages between Mass- and Energy Transfer. 119 2.1.7 Conservation of Mass. 119 2.2 Air Transfer .. 120 2.2.1 In General 120 2.2.2 Air Pressure Differences. .. 121 2.2.2.1 Wind 121 2.2.2.2 Stack Effects.. 122 2.2.2.3 Fans 123 2.2.3 Air Permeances. 124 2.2.4 Air Transfer in Open-porous Materials 127 2.2.4.1 Conservation of Mass. 127 2.2.4.2 Flow Equation. . 128 2.2.4.3 Air Pressures.. 128 2.2.4.4 One Dimension: Flat Walls . 129 2.2.4.5 Two- and Three-dimensions. 131 2.2.5 Air Flow Through Permeable Layers, Apertures, Joints, Leaks and Cavities .. 132 2.2.5.1 Flow Equations. 132 2.2.5.2 Conservation of Mass, Equivalent Hydraulic Circuit. 132 2.2.6 Combined Heat- and Air Transfer . 133 2.2.6.1 Open-porous Materials 133 2.2.6.2 Air Permeable Layers, Joints, Leaks and Cavities.. 140 2.3 Vapour Transfer 143 2.3.1 Water Vapour in the Air 143 2.3.1.1 Overview. 143 2.3.1.2 Quantities 143 2.3.1.3 Maximum Vapour Pressure and Relative Humidity. . 144 2.3.1.4 Changes of State in Humid Air 148 2.3.1.5 Enthalpy of Moist Air. 149 2.3.1.6 Characterizing Moist Air .. 149 2.3.1.7 Applications .. 150 2.3.2 Water Vapour in Open-porous Materials 156 2.3.2.1 Overview. 156 2.3.2.2 Sorption Isotherm and Specific Moisture Ratio 156 2.3.2.3 The Physics Behind .. 158 2.3.2.4 Impact of Salts . 160 2.3.2.5 Consequences .. 161 2.3.3 Vapour Transfer in the Air .. 161 2.3.4 Vapour Transfer in Materials and Construction Parts 164 2.3.4.1 Flow Equation. . 164 2.3.4.2 Conservation of Mass. 166 2.3.4.3 Vapour Transfer by 'Equivalent' Diffusion .. 167 2.3.4.4 Vapour Transfer by (Equivalent) Diffusion and Convection 183 2.3.5 Surface Film Coefficients for Diffusion 190 2.3.6 Some Applications.. 193 2.3.6.1 Diffusion Resistance of a Cavity .. 193 2.3.6.2 Cavity Ventilation. .. 194 2.3.6.3 Water Vapour Balance in a Room in Case of Surface Condensation and Drying. 196 2.4 Moisture Transfer 197 2.4.1 Overview. 197 2.4.2 Moisture Transfer in a Pore . 197 2.4.2.1 Capillarity 197 2.4.2.2 Water Transfer . 200 2.4.2.3 Vapour Transfer 209 2.4.2.4 Moisture Transfer 211 2.4.3 Moisture Transfer in Materials and Construction Parts 211 2.4.3.1 Transfer Equations .. 211 2.4.3.2 Conservation of Mass . 214 2.4.3.3 Starting, Boundary and Contact Conditions.. 215 2.4.3.4 Remark .. 216 2.4.4 Simplified Moisture Transfer Model 216 2.4.4.1 Assumptions .. 216 2.4.4.2 Applications .. 218 2.5 Problems. 233 2.6 References. 251 3 Combined Heat, Air and Moisture Transfer 255 3.1 Overview. 255 3.2 Assumptions.. 255 3.3 Solution.. 255 3.4 Conservation Laws .. 256 3.4.1 Conservation of Mass. 256 3.4.2 Conservation of Energy 258 3.5 Flow Equations. 260 3.5.1 Heat 260 3.5.2 Mass, Air. 260 3.5.2.1 Open Porous Materials 260 3.5.2.2 Air Permeable Layers, Apertures, Joints, Cracks, Leaks and Cavities.. 261 3.5.3 Mass, Moisture . 261 3.5.3.1 Water Vapour .. 261 3.5.3.2 Water. .. 261 3.6 Equations of State 262 3.6.1 Enthalpy/Temperature and Water Vapour Saturation Pressure/Temperature .. 262 3.6.2 Relative Humidity/Moisture Content 262 3.6.3 Suction/Moisture Content. .. 262 3.7 Starting, Boundary and Contact Conditions.. 262 3.7.1 Starting Conditions.. 262 3.7.2 Boundary Conditions . 262 3.7.3 Contact Conditions .. 263 3.8 Two Examples of Simplified Models 263 3.8.1 Heat, Air and Moisture Transfer in Non-Hygroscopic, Non-Capillary Materials 263 3.8.2 Heat, Air and Moisture Transfer in Hygroscopic Materials at Low Moisture Content265 3.9References 266 4 Postscript 269