Why it works
Solar gain explained
Short answer
Solar gain is heat added when sunlight reaches surfaces or passes through glass and is absorbed indoors.
The simple explanation
- ✓East windows gain morning sun.
- ✓West windows can drive late-day overheating.
- ✓External shade stops sunlight before it reaches the glass.
Why it works
This advice follows UK Health Security Agency guidance and the underlying principles of solar gain and radiation.
Important exceptions
Safety, health, weather and the design of your home can change what is appropriate. Stop if an action makes conditions worse.
Related guides
Sources & evidence
Reviewed 2026-08-21
- UK Health Security Agency: Beat the heat: keep cool at home checklist ↗
Supports: Shading, ventilation, reducing indoor heat and protecting people at higher risk.
official guidance · Accessed 2026-08-21