ROOF TYPE
Composition (asphalt shingles)
· ranges from low-cost 3-tab shingle to architectural shingles with extra durability and style
· many colors, types, and manufacturers
· fire resistant
· scars easily when hot
· environmentally unfriendly
· composition roofing material absorbs and holds more heat than wood shake or shingles.
· The asphalt base of composition roofing absorbs the sun's rays and radiates heat for a longer period of time than wood.
· Lighter-colored composition roofs absorb less heat than darker-colored ones.
Wood,shingles or shake
· natural look weathering to a soft grey
· offers some insulation value
· blends in with the environment
· easy to repair or replace
· long lasting if maintained (30–50 years)
· usually requires professional installation high maintenance
· tends to rot, split, mold, and mildew
· poor fire rating unless presure treated
· Wood does not conduct heat.
· Wood shakes are also individual pieces that allow air to circulate.
Metal (steel, aluminum, tin, copper)
· available in different looks including cedar shingles, slate, or standing seam
· may be difficult to install
· can be expensive
· may need periodic painting
· have inherent properties that cause roofs constructed with these materials to become exceptionally hotter than other roofs.
· absorb most of the energy reaching them from the sun (high thermal absorption), reflect little energy (low reflectivity), and conduct heat very rapidly (high thermal conductivity).
· Therefore, there are special design considerations for underlayments used under these metal roofs, due to the high in-service temperatures that these roof assemblies can reach.
Tile (concrete, clay)
· many colors and styles
· attractive
· fireproof
· easy to maintain
· extremely durable when maintained
· fragile; walking on roof may break tiles
Slate
· beautiful, distinctive appearance
· fireproof
· long life span
· low maintenance
· heavy
· fragile
Thursday, October 9, 2008
Monday, October 6, 2008
ACID AND BASES
AIR
air is the most important thing for life things in this world because in air are contains oxygen, hydrogen and many more gases..Air is a mixture of variety of gases, air is the life sustaining substence for animal and human water vapour and small amounts of other elements , Higher in the atmosphere. People can only clearly notice the prescence of air when the wind blows.The air we breathe consists mostly of the following gases:
Oxygen (O2)20%
Noble gasses1%
Carbon dioxide (CO2)0,03%
Brick, Roof and Tile
Heat is one of energy that we cant create, cannot be destroy but can transfer from one matter to the other matter which is solid, water even gases. In our life, heat is very important for example, heat is using for cooking, decayed process and combustion process. But too much heat will be a problem to our life. For example, in construction to build a house, we have to prevent the heat so that we can have a comfort house to live in. in order to do that we have to use a batter roof to prevent the heat from enter the house. Brick, roof and tile is use to decreasing the temperature in the house. Bricks are divided by their formation and their composition such as common brick, face brick, clinker brick, press brick and many more. Common brick is use generally to build a buildings because its hard and more durable kinds are preferred for this purpose.
Monday, July 14, 2008
WHAT IS ELECTRICITY
Electricity is so much part of our lives in this modern world that we take it very much for granted. Only when there is an electrical breakdown are we reminded how dependent we have become on it. Electricity does so many things for us. Without it our modern way of living will be severely affected or even impossible. It is beneficial for us to understand it better and thus appreciate its important role in our lives.
Electricity is simply the flow of electrically charged particles through a conductor. A common conductor is the electrical wire. In this wire the electrically charged particles are electron of the metallic conductor. These electrons can be made to move through the wire by a generator, an electric cell of other means. The movement of these electrons through the wire is that we call electricity. When connected to an electrical appliance, the energetic electrons give some of their energy to the appliance thus making it work. For example, electrons passing through the filament of a light bulb causes the filament to hear up and give out light.
Other appliances work on different principles but basically they all get their energy from the movement of the electrons through them.
A lightning bolt is actually the movement of charge particles from a cloud to another or to the earth. The conductor is the air itself. As we all know, this form of electricity is very powerful indeed. A person struck by lightning is liable to get roasted. Even our household electrical supply is a very powerful. One can get electrocuted by it.
Electricity drives so many appliances in our modern world. The radio, television, iron, refrigerator, computer pocket calculator, fan, light bulb, motor and hundreds of other devices all require electricity in order to work. If we did not know how to use electricity our world not be as it is now. Can you imagine life without the radio, television, fan, or the light bulb? Well, we would not have these things without electricity.
Electricity, for all its wonder and usefulness, is not easy to store. Except for batteries, hardly anything else can store electricity in sufficient amounts. So in order to get this precious energy we need to convert it from other forms of energy.
The most common way of generating is by using a generator. But to run a generator we need other sources of energy. We make us of coal, water, oil, energy from the sun, atomic energy and other sources to drive our generators. So day and night we use up other sources or energy to supply us with electricity. We have become so dependent on it. Without it our world will be entirely different. Perhaps some time in the future we may be able to discover something else that can replace our dependence on electricity. Till that time however, we have to go on using it.
Electricity is simply the flow of electrically charged particles through a conductor. A common conductor is the electrical wire. In this wire the electrically charged particles are electron of the metallic conductor. These electrons can be made to move through the wire by a generator, an electric cell of other means. The movement of these electrons through the wire is that we call electricity. When connected to an electrical appliance, the energetic electrons give some of their energy to the appliance thus making it work. For example, electrons passing through the filament of a light bulb causes the filament to hear up and give out light.
Other appliances work on different principles but basically they all get their energy from the movement of the electrons through them.
A lightning bolt is actually the movement of charge particles from a cloud to another or to the earth. The conductor is the air itself. As we all know, this form of electricity is very powerful indeed. A person struck by lightning is liable to get roasted. Even our household electrical supply is a very powerful. One can get electrocuted by it.
Electricity drives so many appliances in our modern world. The radio, television, iron, refrigerator, computer pocket calculator, fan, light bulb, motor and hundreds of other devices all require electricity in order to work. If we did not know how to use electricity our world not be as it is now. Can you imagine life without the radio, television, fan, or the light bulb? Well, we would not have these things without electricity.
Electricity, for all its wonder and usefulness, is not easy to store. Except for batteries, hardly anything else can store electricity in sufficient amounts. So in order to get this precious energy we need to convert it from other forms of energy.
The most common way of generating is by using a generator. But to run a generator we need other sources of energy. We make us of coal, water, oil, energy from the sun, atomic energy and other sources to drive our generators. So day and night we use up other sources or energy to supply us with electricity. We have become so dependent on it. Without it our world will be entirely different. Perhaps some time in the future we may be able to discover something else that can replace our dependence on electricity. Till that time however, we have to go on using it.
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