Choosing building materials

Transcription

1 Choosing building materials clay (click for more) straw bale copper stone Plastic (click for more) metals (click for more) bamboo wood (click for more) sand Can I reduce the environmental impact of my building by choosing materials carefully?

2 materials The construction of buildings uses a huge amount of materials. We need to try to work out the impact of different, commonly used building materials and try to decide which is the most appropriate for our building. soil (click for more) wood (click for more) stone sand - to make glass limestone makes cement to make concrete (click for more) iron ore to make steel (click for more) clay and calcium silicate to make bricks oil plastics (click for more)

3 What are the materials issues? What s the embodied energy of the possible materials I might use? How much of the material is left am I depleting already scarce resources? Is it a renewable or non-renewable material? What is the thermal mass of the material?

4 Embodied energy The embodied energy of a material is the amount of energy that has gone into extracting it producing it transporting it to the site. It s like the amount of energy locked up in the material.

5 Can you use existing materials? Rocks used as a shower wall, a wagon wheel used as a window frame.

6 materials How much of it is available? Plentiful Questions to think about: Is it available on the site? Or locally? Will it require a lot of energy to process? Scarce As well as being scarce, how much energy do they use in production? Can they be re-used/ recycled? Oil for plastics Clay Other metals (eg zinc) Earth Lead used on roofs Straw bale Stone Copper for pipes

7 materials How much is left of each material on the planet? Years left of different materials assuming current rate of use

8 materials Materials can be categorised in different ways. - renewable / non renewable - plentiful / scarce Examples: Stone is plentiful but not renewable. Oil is non-renewable and scarce. Renewable These are materials which will be replenished naturally. How plentiful they are depends on how much land we have available to grow them, and how fast they grow. These resources shouldn t be used faster than they can be replenished. Examples: Bamboo: very fast growing but not indigenous to the UK Non-renewable These are materials which are available in finite quantities, ie once we have used them all up, there will be not be replenished. Examples: Plastics (from oil) Corrugated plastic Wood: as long as you replant it, it is renewable Hemp: Very fast growing in the UK. Steel (from iron ore)

9 When using non renewable or scarce materials (such as plastic and metal) there are some questions to think about: Can it be used as little as possible? Can it be re-used, or recycled afterwards? Is it really vital to use it? Can another more readily available or more sustainable material be used instead?

10 What s thermal mass got to do with material choices? Thermal mass is the ability of a material to absorb heat energy. A lot of heat energy is required to change the temperature of high density materials like concrete, bricks and tiles. They are therefore said to have high thermal mass. Lightweight materials such as timber have low thermal mass. The lower the thermal mass, the better. Winter Allow thermal mass to absorb heat during the day from direct sunlight or from radiant heaters. It will re-radiate this warmth back into the home throughout the night. Summer Allow cool night breezes and/or convection currents to pass over the thermal mass, drawing out all the stored energy. During the day protect thermal mass from excess summer sun with shading and insulation if required.

11 Thermal mass at CAT The internal wall of this building is made of rammed earth which has a high thermal mass. It warms up when the sun hits it. At night, or when the temperature decreases, the heat stored in the wall comes out, keeping the building at a more constant temperature, and reducing the heating demand.

12 Woodman s Cottage, Sussex What s good about Ben Law s house?

13 Ben s house. - Uses materials with low 'embodied energy i.e. local, have not travelled long distances and do not require large amounts of energy to produce - Re-uses old materials (e.g. newspapers) - Use recycled materials (e.g. front door) - Minimizes waste (e.g. rainwater harvesting)

14 Olympia s house in Peru In 1990 an earthquake in Alto Mayo, North Peru destroyed 3000 houses and damaged 5000 more The affected houses were earth-based structures that were unable to withstand tremors walls cracked and collapsed. The builders were unaware of a traditional technology (called quincha) that had built-in earthquake resistance. Practical Action, a development charity, worked with local people to develop earthquake resistant housing.

15 Olympia and quincha mejorada Olympia Guerra was one of people affected who became involved in designing and making new homes Quincha mejorada (improved traditional homes) used the following improvements concrete foundations (greater stability) tar-treated columns concreted into the ground (protected against humidity) vertically woven canes in the walls (greater strength) All the materials were available locally and cheaply roof beams and roofing materials nailed down (wind resistance) use of wires to tie beams and columns (protect against earth movement)

16 The results In 1991 a second tremor hit the same region 9000 further homes were destroyed or damaged all 70 new quincha mejorada homes survived 4000 further homes were built plus schools and community centres, using the same quincha mejorada techniques

17 So, how did you do?