Issues to considering during selection of materials 3

• Material are usuallly classified into renewable and non=renewable maerials . 
• Non=-renewable materials include those with regenerationc uycles of millennia (e.g. coal , oil , etc) 
• Renewable materials include those with regeneration cycles of decades or less (e.g. timber , flax , cork ) 

1. Material can be plentiful or scarce 
2. Sand is considered to be a plentiful resource , where oil reserves are limited 
3. Renewable resources are generally considered to plentiful . 
4. However , if a renewable material is over=harvested , it may become scare and ultimately even depleted 
5. To avoid over-harvested , resources have to be managed . 

• Extraction of harvesting process can afect the surrounding environment ( associated with pollution , destruction of natural habitats , and reduction of biodiversity ) . 
• Pollution of water , soil and air can also be a consequence of material extraction 
• Extraction of oil cause air pollution from flaring and marine or groundwater pollution from oil leaks and spills . 

1.  Materials are rarely used in their completely natural state 
2. Preparation of manufacturing process is generallly necessary to create a uusable building product 
3. Impact asociated with manufacturing can include pollution to air  , water and ground . 
4. Manufacturing also generally requires energy , which is mainly derived from fossil fuel and is associated with global warming and pollution .

• Producion of PVC one of the materials being seriously environmentally damaging , is associated with emissions toxic . 
• Production , usage and disposal of building materials in accounts for significant quantity of energy and resources . 
• E.g. Co2 emissions were related to mnanufacture and transport of building materials . 
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