This example compares assumed solar gains through glazing. It predicts neither room temperature nor overheating hours in a real home.
Model assumptions
Glazing area A = 10 m² and g = 0.50. Illustrative orientations A and B receive 500 and 300 W/m² at one instant; these are not climate data for a specific city.
Formula and result
The simplified balance is P = A × I × g × F, with F = 1 unshaded. Results are 2500 W for A and 1500 W for B. Assumed F = 0.30 reduces them to 750 and 450 W.
Meaning of the comparison
Shading changes gains at a given instant, while orientation affects the irradiation time profile. One hour cannot establish that one façade is always better.
Sensitivity and next step
In this linear model, doubling area doubles gains if everything else stays fixed. Annual decisions need hourly weather, shading geometry and actual glazing and shading properties.
Overheating limitations
Room temperature also depends on mass, ventilation, envelope, occupants and controls. The table models gains, not absence of overheating or required air-conditioner capacity.
| Item | Parameter | Check / result |
|---|---|---|
| A: 500 W/m² | F = 1 → 0.30 | 2500 → 750 W |
| B: 300 W/m² | F = 1 → 0.30 | 1500 → 450 W |
| A = 10 m² | g = 0.50 | Assumed inputs |
What this means for your project
Compare orientations and shading with a climate time series. Comfort assessment needs a full room model, not this formula alone.
Sources and scope of review
Related reading
- Summer Overheating: Why Highly Insulated Homes Can Still Overheat
- Shading from Trees and Neighbouring Buildings
- Panoramic Glazing in an Energy-Efficient Home: Where Is the Limit?
- External Shading: Shutters, Louvres and Overhangs