The materials from which a building is constructed make a significant contribution to its overall impact on the environment. This impact is felt in a number of ways; locally. through the effects of activities such as quarrying; globally, as a result of carbon dioxide released by using energy used to manufacture the materials; and internally, in the effects on the health of the occupants of the building. Some of these effects are easier to measure than others. and comparisons between the seriousness of the different effects are difficult to make.