What is the contribution of old cars to air pollution?

As well as designing buildings which are more energy efficient also suggested for hotter climates is the possibility of using lighter-coloured, more reflective materials in the development of urban areas (e.g. by painting roofs white) and planting trees , . This saves energy because it cools buildings and reduces the urban heat island effect thus reducing the use of air conditioning. In cold climates where air conditioning accounts for only a small proportion of energy consumption, the opposite of this approach may be preferable: An increase in average city temperatures by painting roofs black decreases demand for heating fuel.