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 = hi A (Ti - T{si}) = \frac{A (T{se} - T{si})}{Rw} = he A (T{se} - T_e)
  • T{fs} = T{se} + \frac{aW}{he} W_i
  • Φ = hi A (Ti - T{si}) = \frac{A (T{se} - T{si})}{Rw} = he A (T{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 = tW + aW \frac{he}{Ug}
• Equations:
  • Φ = Ug A (Te - Ti) + g Wi A
  • Φ = Ug A (Te - Ti) + (tW + aW \frac{he}{Ug}) Wi A
  • Φ = Cs g^* Wi A + Ug A (Te - 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) = Tm + θ0 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{fs} - Ti)
  • Φ(τ) = U A [T{fs}(τ) - Ti]

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.