Thermal performance and building geometry

Thermal performance of a building is how well the building keeps indoor temperature comfortable with little energy, by controlling heat gain and loss through its envelope. It depends on U-value, solar gain, ventilation, and thermal mass.

The statement is correct. The two factors named control most of the heat exchange.

Geometric dimensions

• Surface-area-to-volume ratio: A compact shape (cube) has a smaller external area per unit volume, so heat loss in winter and gain in summer is less. Long, spread plans lose more.
• Orientation and aspect ratio: A building elongated along east-west with its long side facing south gets more winter sun and less low-angle east-west sun.
• Window size and position: Glass area gives solar gain and conduction loss. Overhang depth, roof height and room depth control shading and daylight.
• Ceiling height: High ceilings let hot air rise away from occupants and aid stack ventilation.
• Wall and roof thickness: Thick elements give more resistance ($R = t/k$) and time lag.

Material properties

• Thermal conductivity (k): Low k (AAC blocks, hollow bricks, insulation) reduces heat flow; high k (steel, glass, stone) increases it.
• Thermal mass (specific heat and density): Heavy materials (stone, mud, concrete) store heat and delay it (time lag), reducing temperature swing.
• Surface properties: Colour (absorptivity) and emissivity decide how much radiation is absorbed or reflected.

Thus a good design gives a compact geometry with right orientation and uses suitable materials. Neither alone is sufficient.