Integrated Building Systems 1 PDF

Module 1 Envelope 1 Integrated Building Systems 1 Module1: Rawad El Kontar Announcements Previously on IBS 1 Previously on IBS 1 1. Mechanical Work : Amount of energy transfer by a force acting through distance (Nm, J) 2. Energy: The ability to do work units Joules (Nm, J) 3. Power: Work done...

Module 1 Envelope 1 Integrated Building Systems 1 Module1: Rawad El Kontar Announcements Previously on IBS 1 Previously on IBS 1 1. Mechanical Work : Amount of energy transfer by a force acting through distance (Nm, J) 2. Energy: The ability to do work units Joules (Nm, J) 3. Power: Work done within a specific amount of time (J/s) 4. Heat: Thermal energy transferred between objects due to temperature difference (kWh) 5. Temperature: A measure of Thermal energy held by a body of matter (Celsius , Fahrenheit, Kelvin) 6. The total energy of a closed system remains constant. Previously on IBS 1 8. In a closed system, heat flows spontaneously from a region of higher temperature to one with lower temperature 9. Equilibrium state or thermal balance is achieved when the net transfer of energy is zero 10. What is Rawad’s first pet ? ∆𝑈 = 𝑄 − 𝑊 Give and Take (and Keep Doing it) Equilibrium is a state of balance between continuing processes Where, ∆𝑈 = 𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑖𝑛𝑡𝑒𝑟𝑛𝑎𝑙 𝑒𝑛𝑒𝑟𝑔𝑦 𝑄 = ℎ𝑒𝑎𝑡 𝑎𝑑𝑑𝑒𝑑 𝑡𝑜 𝑡ℎ𝑒 𝑠𝑦𝑠𝑡𝑒𝑚/building 𝑊 = 𝑤𝑜𝑟𝑘 𝑑𝑜𝑛𝑒 𝑏𝑦 𝑠𝑦𝑡𝑒𝑚/𝑏𝑢𝑖𝑙𝑑𝑖𝑛𝑔 Equilibrium state or thermal balance is achieved when the net transfer of energy is zero Static Equilibrium Dynamic Equilibrium Architectural Thermodynamics Question ? Cold Climate Design VS Hot Climate Design Hot Climate Design Cold Climate Design How is Heat transferred ? Sources of Heat Conduction Convection Radiation Sources of Heat Conduction Heat transfer by physical contact Convection Radiation Sources of Heat Conduction Convection Heat transfer by movement of a fluid Radiation Sources of Heat Conduction Convection Radiation Heat transfer by waves/particles Building Envelope What is a building Envelope ? What is the Building Envelope? What is a building Envelope ? A cohesive definition encompasses all elements of the building What is a building Envelope ? Main 3 parts: One widely used definition would be that of what envelopes the conditioned space of the building • External walls • Roofs • Vertical fenestrations Key Concepts • U-value / Thermal Transmittance • Solar Heat Gain Coefficient ( SHGC) • Window Wall Ration (WWR) • Skylight Roof Ration ( SSR) • Solar Reflectance Index ( SRI) • Visual Light Transmission (VLT) Thermal Transmittance or U-value • Thermal transmittance is the rate of transfer of heat through matter • The thermal transmittance of a material or an assembly is expressed as a U-value. • U-value considers heat transfer from all 3 heat transfer modes ( conduction, convection , radiation) What are the thermal processes affecting the Envelope? Outside (92 F) Inside (68F) The building envelope is constantly being affected by a multitude of heat sources using the 3 forms of heat transfer identified earlier How much heat is transferred through the wall ? What are the thermal processes affecting the Envelop T1 > T2 Fourier’s Law of Conduction T1 T2 q x0 xL = thermal conductivity (W/m*K) = amount of heat transferred through a material (W , J/s) = difference in temperature (K) Fourier’s Law of Conduction Heat transfer through the wall’s different layers What are the thermal processes affecting the Envelope? Outside (92 F) = thermal conductivity (W/m*K) = amount of heat transferred through a material = difference in temperature (K) Inside (68 F) k1 k2 k3 k4 What are the thermal properties of a material? (Thermal Conductivity): Ability to conduct heat (W/mk) (Thermal Diffusivity): How quickly it reacts to temperature (m2/s) 𝑝 (Specific Heat Capacity): How much energy is needed to change the temperature (Material Density): How much of the substance exists (mass) in a volume (kg/m3) are the thermal properties of a material? R value is mainly used for Walls and Roofs • Thermal resistance ( R ) is directly proportional to the thickness of a wall is the R Value [ 𝑚B 𝐾/𝑊 ] is Thermal Conductivity is the thickness of the material • Thermal resistance is inversely proportional to the thermal conductivity. What are the thermal processes affecting the Envelope? Resistance of Multiple Layers Outside (92 F) Rse R3 R2 R15 R3 Rsi Inside (68 F) R Value is additive is additive in R an electrical circuit R Total = Rsejust+asRCurrent + R + R + + R 1 2 3 4 si Rtotal=R1+R2+R3+R4 Rsi = Interior surface thin air thermal resistance (constant) Rse = Exterior surface thin air thermal resistance (constant) is the R Value is the U Value Example Question: Calculate U-value for the wall AAC Block 200 mm XPS Insulation 50 mm R2 Rse = 0.04 Rsi = 0.13 Example Question: After calculating U-values for the wall what wall would you choose for a cold climate and why ? Solar Reflectance Index • Solar Reflectance Index (SRI) is expressed as a fraction which combines the material properties of emissivity and reflectivity. • It indicates the ability of material to reflect heat • It is represented as a ratio or percentage Reflectivity of Different Materials