Building Envelope Characteristics for Thermal Flux Assessment

Opaque Wall Exposed to the Sun

• Fictitious temperature ($T_{fs}$) considers heat exchange contributions.
• In stationary conditions, thermal power received equals thermal power passing through the wall.
• Equations:
  • $Φ = h<em>i A (T</em>i - T<em>{si}) = \frac{A (T</em>{se} - T<em>{si})}{R</em>w} = h<em>e A (T</em>{se} - T_e)$
  • $T<em>{fs} = T</em>{se} + \frac{a<em>W}{h</em>e} W_i$
  • $Φ = h<em>i A (T</em>i - T<em>{si}) = \frac{A (T</em>{se} - T<em>{si})}{R</em>w} = h<em>e A (T</em>{fs} - T_e)$

Transparent Wall Exposed to the Sun

• Heat input through glass transparency must be considered.
• Superimposition separates temperature difference and solar radiation effects.
• g is the solar gain coefficient or solar factor.
• $C_s = \frac{g}{g^*}$
• $g = t<em>W + a</em>W \frac{h<em>e}{U</em>g}$
• Equations:
  • $Φ = U<em>g A (T</em>e - T<em>i) + g W</em>i A$
  • $Φ = U<em>g A (T</em>e - T<em>i) + (t</em>W + a<em>W \frac{h</em>e}{U<em>g}) W</em>i A$
  • $Φ = C<em>s g^* W</em>i A + U<em>g A (T</em>e - T_i)$

Energy and Light Characteristics of Glasses

• Presents a table of various glass types with their energy and light characteristics.
• Includes properties like thickness, transmittance (t), reflectance (r), absorbance (a), solar gain coefficient (g), shading coefficient (Cs), U-value (Ug), and color rendering.

Wall Subjected to a Periodic Temperature Regime

• Real walls have complex behavior due to inertia effects.
• Winter: Limited inertia effects when average external temperature is lower than internal.
• Summer: Thermal inertia must be evaluated when average external temperature is close to internal.

Semi-finite Medium in Stabilized Periodic Regime

• Analyzes a semi-infinite medium under periodic temperature.
• $T(x, \tau) = T<em>m + θ</em>0 e^{-βx} sin(ωτ - βx)$
• $β = \sqrt{\frac{π}{Dτ_0}}$
• $D = \frac{λ}{ρc}$

Real Opaque Wall Subjected to a Periodic Regime

• Real walls differ from semi-infinite mediums due to finite size and interaction with external and internal air.
• High thermal inertia walls respond to the 24-hour average fictitious temperature.
• No thermal inertia walls instantly follow external stress.
• Equations:
  • $Φ = U A (T<em>{fs} - T</em>i)$
  • $Φ(τ) = U A [T<em>{fs}(τ) - T</em>i]$

Real Opaque Wall Subjected to a Periodic Regime

• Real wall behavior is intermediate.
• Heat exchange depends on the equivalent temperature difference.

Summary Considerations

• Winter: Evaluate heat transmission using transmittance only.
• Summer: Consider inertia effects.
• Inertia is important for opaque parts only.
• Solar radiation on opaque parts is considered via fictitious temperature.
• Solar radiation on transparent parts is separate from convection effects.