Cleaner Pakistan Climate and Building Design
Building Structural/Construction Systems • The combinations of materials used to build the main elements of our homes: roof, walls and floor are referred to as construction systems. They are many and varied and each has advantages and disadvantages depending on climate, distance from source of supply, budget and desired style and appearance. The different building systems are: • The traditional kacha houses with walls of sun dried mud ( adobe) and wooden roof. Wooden frames provided as bonds at different levels along the length of walls. • Bhonga houses with conical roof of inner dia 3 to 6 m with adobe walls and bamboo framed roof covered with thatch. The walls also having wooden frames.
Single story brick/ Block masonry houses with reinforced concrete roofs. Ext. Wall: 13.5 in , Int. Walls: 9 in Block masonry: 8 in – Wooden roof truss with CGI sheets or RCC 4 in thick slab. • Stone masonry walls and Wooden and CGI sheets roofs. Stone masonry walls and RCC roofs • Reinforced Concrete Structures. Frame structures with columns, beams and slab connections.
Conditions in selection of structural systems • 1. Soil conditions • 2. The program and concept • 3. Applicable codes • 4. Potential code changes • 5. Flexibility • 6. Impact on finished-ceiling and building height • 7. Material delivery and construction timing • 8. Local construction capabilities and preferences • 9. Ease of construction and schedule • 10. Cost of the selected system • 11. Cost impact on other systems • 12. Appearance and aesthetic potential
Environmental Considerations in Selecting the Building Structure System • Make more efficient use of existing materials. • Minimize the amount of waste. • Use materials with least environmental impact. • Consider both operational and whole lifecycle performance of materials and designs. • Use fully recycled materials or materials with recycled content. • Re-use whole buildings or parts thereof to reduce consumption of new materials. • Choose materials with a lifespan equivalent to the projected life of the building. • Design to extend building lifespan (current average 50 years - aim for 100+).
Design and build for de-construction, re-use, adaptation, modification and recycling. • Encourage development of new, efficient, low impact materials and applications by creating demand. • Consider how and where the materials are sourced and the impacts this causes. • Minimize the energy used to transport materials by using locally produced material. Use of lightweight material where appropriate also reduces transportation energy. • Minimize the energy used to heat and cool the building by using materials that effectively modify climate extremes. • Understand how chemicals used in the manufacture of some materials might affect your health. • Minimize or eliminate emissions during use and manufacture.
1. Mud brick (Adobe) • The ideal building material would be 'borrowed' from the environment and replaced after use. There would be little or no processing of the raw material and all the energy inputs would be directly, or indirectly, from the sun. This ideal material would also be cheap. Mud bricks come close to this ideal, or they can do. • The appearanceof mud bricks reflects the material they are made from. They are thus earthy, with color determined by color of clays and sands in the mix. Finished walls can express the brick patterns very strongly at one extreme or be made into a smoothly continuous surface.
Performance parameters of Mud • Structural capability • With thick enough walls, mud brick can create load bearing structures up to several stories high. • Thermal mass • Adobe walls can provide moderate to high thermal mass, but for most climatic conditions, as a rule of thumb, walls should be a minimum of 300 mm ( 12in) thick to provide effective thermal mass. • Insulation • Contrary to popular belief mud bricks are not good insulators. Since they are extremely dense they lack the ability to trap air within their structure. Insulation can be added to adobe walls with linings. • Fire and vermin resistance • Since earth does not burn, and earth walls do not readily provide habitat for vermin, mud brick walls generally have excellent fire and vermin resistance.
Durability and moisture resistance • Adobe walls are capable of providing structural support for centuries but they need protection from extreme weather (eg. with deep eaves) or continuous maintenance (the ancient structures of the Yemen have been repaired continuously for the centuries they have been standing). As a general rule, adobe needs protection from driving rain (although some adobe soils are very resistant to weathering) and should not be exposed to continuous high moisture. • Breath-ability and toxicity • Mud bricks make 'breathable' walls but some mud brick recipes include bitumen, which potentially results in some out gassing of hydrocarbons. Ideally earth should be used in its natural state or as near it as can be achieved.
Sustainability (Environmental impacts) • Mud bricks have the potential to provide the lowest impact of all construction materials. Adobe should not contain any organic matter • Build-ability, availability and cost • Mud bricks provide a forgiving construction medium well suited to owner-builder construction.
2. Concrete slab floors • Concrete slab floors come in many forms and can be used to provide great thermal comfort and lifestyle advantages. • Benefits: • Thermal Mass describes the potential of a material to store and re-release thermal energy. Highest here • Durability is one of the other main advantages of concrete slabs. • Termite resistance is achieved with concrete slabs by designing and constructing them in accordance with the code.
Design parameters of Concrete slabs • Passive solar design principles and high mass construction work well together, and concrete slabs are generally the easiest way to add thermal mass to a house . • Natural ventilation must be provided for in the design • Insulation of the slab edge is important in cooler climates, to prevent warmth escaping through the edges of the slab • Balconies extended from the main slab of a house may act as cooling or heating fins, carrying precious warmth away to the cold exterior during winter, or transferring heat from summer sun inside . • Acoustics need to be considered.
3. Clay brick • Clay brickwork is made from selected clays that are molded or cut into shape and fired in ovens. • The firing process transforms the clay into a building component with high compressive strength and excellent weathering qualities, attributes that have been exploited for millennia to build structures ranging from single-storey huts to enormous viaducts. • Clay brickwork is most widely used in external cladding and load bearing wall medium and continues to enjoy rapid growth in its use.
Performance Summary • Appearance • Clay brickwork is available in a great variety of natural colors and textures derived from fired clay used in combination with cement mortar joints of various colors and finishes. • Structural capability • The high compressive strength of fired clay bricks has been exploited for millennia to build structures ranging from single-storey huts to massive public buildings and enormous bridges and viaducts. • Thermal mass • Clay brickwork has high thermal mass.
Insulation • Clay brickwork, combined with internal and external air films and a cavity, has moderate thermal resistance. • Sound insulation • Due to their mass, clay bricks provide excellent sound insulation, particularly for low frequency noise. • Vermin resistance • Clay brickwork consists of dense inorganic materials that do not harbor vermin.
Sustainability (environmental impacts) • Clay brick manufacture uses energy but the investment of embodied energy is repaid by the longevity of the material. • Clay brick homes have a long life and low maintenance costs making them a potentially sustainable form of construction. • Option 1: Brick veneer/timber frame/concrete slab • Option 2Brick veneer/steel frame/concrete slab • Option 3Double brick/concrete slab • Option 4Timber clad/steel frame/concrete slab • Option 5Timber clad/timber frame/concrete slab
4. Lightweight timber • Wooden structures have been used in all kinds of building types for many years. • In a world living with the effects of global warming, timber provides a renewable building material that stores carbon in its production.
Performance Summary • Appearance Aesthetically, timber possesses a natural attractiveness that people readily relate to. • Structural capability Timber has good compressive strength but is strongest in tension • Thermal mass In general timber has low thermal mass • Insulation Timber is a natural insulator due to air pockets within its cellular structure
Sound insulation The sound insulation of walls is usually obtained by providing a barrier of sufficient mass to absorb the sound energy. • Fire Resistance: very low • Durability and moisture resistance Timber is an organic material and deteriorates due to weathering. • Toxicity and breath ability: Timber is generally non-toxic.
Sustainability (environmental impacts) • Timber is a renewable building resource that absorbs carbon it its production. • A lightweight timber construction can be built for deconstruction, and timbers from the construction reused or recycled at the end of its use in the building. • It has tremendous capacity to provide a sustainable construction option. • Timber is completely biodegradable and can even be composted if no reuse application can be found. • Build ability, availability and cost • Lightweight timber construction is relatively simple to build.
Choice of Appropriate Building Materials • The "appropriateness" of a building material or construction technology can never be generalized. • The following questions show some of the main factors, which determine appropriateness: • Is the material produced locally, or is it partially or entirely imported? • Is it cheap, abundantly available, and/or easily renewable? • Has it been produced in a factory far away (transportation costs!);
Does it require special machines and equipment, or can it be produced at lower cost on the building site? (Good quality and durability are often more important than low procurement costs). • Does its production and use require a high-energy input, and cause wastage and pollution? Is there an acceptable alternative material, which eliminates these problems? • Is the material and construction technique climatically acceptable?
Does the material and construction technique provide sufficient safety against common natural hazards (e.g. fire. biological agents, heavy rain, hurricanes, earthquakes)? • Can the material and technology be used and understood by the local workers, or are special skills and experience required? • Are repairs and replacements possible with local means? • Is the material socially acceptable? Is it considered low standard, or does it offend religious belief? Does it match with the materials and constructions of nearby buildings?
Historical Perspective • John Ruskin (1819-1900) • The Arts And Crafts Movements (William Morris – 1834-1896) • Art Nouveau: 1890-1905 • Victor Horta (1861-1947) • Frank Lloyd Wright (1867-1959) • Design For The Machine Age (1900-1930) • De Stijl (1917 – 1931) • The Bauhaus (1919 – 1933) Recorded Historical Perspective BACK GROUND
Eco Materials Definition :- Materials those have, the lowest possible negative impact to the natural environment, minimal net negative impact to the natural environment, and maintain some reasonable level of human satisfaction in their technological and socioeconomic performance could be defined as "eco-materials".
Eco Materials • Assessment System • Japanese Study • Study By Technical Research Center Of Finland • Study By National Institute Of Building Sciences (USA) • Study By American Institute Of Architect’s Environmental Resource Guides
GUIDELINE PRINCIPAL FOR MATERIALS • Avoid Ozone-depleting Chemicals In Mechanical Equipment And Insulation. • Use Durable Products And Materials • Choose Low-maintenance Building Materials • Choose Building Materials With Low Embodied Energy. • Buy Locally Produced Building Materials • Use Building Products Made From Recycled Materials • Use Salvaged Building Materials When Possible. • Seek Responsible Wood Supplies. • Avoid Materials That Will Off gas Pollutants. • Minimize Use Of Pressure-treated Lumber. • Minimize Packaging Waste.
Construction Material Used In Outer Walls (Percentage) By Rural/Urban 1998
CONSTRUCTION MATERIAL USED IN ROOFS (PERCENTAGE) BY RURAL/URBAN 1998