STONES -materials of sustainability

Post 676 –by Gautam Shah

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SindhuDurg Fort

Stones are procured through collection off the surfaces and by extraction (mining) from depths of the earth. The stones of both types are abundantly available. Major problems with sustainable stone exploration are the economics of transportation. Other issues are cost of size conversion, surface preparation and quality equalization. In future greater attention will have to be for management of stone-wastes at locations of mining and processing.

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Stones are used for their surface quality and structural properties. And in spite of technologically greater capacity to search over wider and deeper terrains, stones always remain scarce or unviable at many places. At use-points natural stones must arrive in optimum mass-units and in forms that are viable for transport, storage and usage.

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Mount_William_Aboriginal_stone_axe_quarry

Stone resources are of basic two types: Surface Stones and Extracted Stones.

Surface Stones show many, but qualitative and size variations. Over a geographic region, though the quality is fairly consistent. Quality equalization can only be enforced through region-based sourcing, selection and separation. Surface-collected materials are naturally formed (boulders, pebbles, gravel, sands, etc.) or wastes of stone processing. Such materials are fractured along the plane of shearing force or across the weakest plane, and so show varied structural properties, colour and grain structure (texture) on different faces. These stones are equally weathered on all faces.

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Extracted Stones materials are loaded (buried) with varying depths of overburden, of the same or different nature of materials. The over burdening mass, protects as well as contaminates the stones. The water passing through the organic soil burden is nominally acidic, and so affects the alkaline stone mass. Fresh lime stones are soft and porous, but when exposed to Carbon dioxide begin to change, harden due to the aeration.

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Typically, igneous (granite, trap) and metamorphic rocks (marble, schist, slate) have nearly crystalline compounds, and are not stratified so do not present any layers or strata. Sedimentary rocks (lime stone, sand stone, soap stone, travertine) are formed of uniform constitution, though stratified, often in inclined and curved formations due to movements in the earth mass. Sedimentary rocks show grains intervened by a cementing medium.

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All stones collected from the surface or mined, must go through some primary processing.

■ Subtractive processes remove excess mass for surface cleaning, sizing, cleaving and pattern sculpting. The processes are, chipping, splitting, cutting, dressing, sculpting, engraving, grinding, polishing etc.

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■ Formative processes do not add any mass but change the spatial or physical characteristics of stone such as its sensorial, structural and environmental behaviour. The treatments include impregnation, edge reinforcing, various types of chemical treatments through acid, alkali, solvent and other oxidative compounds, heat and flame treatments, sintering, spluttering, dying, bleaching etc.

Stacked Stone Forms Pretty Stones Wall Stones

■ Additive processes add to the stone mass. Till very recently technologies involved were of Surface layering by way of coating or cladding. But now ceramic formation, metal alloying and deposition, surface synthesis, surface molecular treatments are being used.

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The sustainability of stone is dependent on basic three aspects: 1 Minimum mass for largest possible surface extent, 2 Reuse of all waste products, 3 New uses for very small sized materials (sand, gravel, pebbles).

1 Stones are valued for their surface qualities, and we need to extend the Surface area. The extended surface reduces the mass / weight of the stone. This can be done by thin sectioning, and by techniques of amalgamation of bits and pieces.

2 Stones have certain structural properties which we can be altered and reinforced. This process starts with new ways of excavation, extraction and conversion of the material. And can be extended to new forms of usage.

3 A new field is emerging on materials’ technology front. This is about creating new materials combinative formations. The formations include various types of composites, geometrical or spatial compositions and combining or ‘synthesizing’ materials of diverse nature. These reconstructive processes include using particulate matter (various grades of fineness such as dust, sands, gravels, pebbles, chips and lumps) as fillers with a matrix of resin or cement. Forming layered composites with sheets or slabs of stone and other materials (polymer sheets, fabrics). Forming amalgamated materials by lamination, co-extrusion, sheet forming, metalizing, ceramic forming, etc. and chemically converting stones into byproducts like minerals and chemicals.

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Sustainable Strategies for Stone

Stone is the least of bio-degrading materials, so not a ‘recoverable or ecological’ material. It can be recycled through reuse processes. Sized blocks of stones for masonry and flooring, have been reused since Egyptian and Roman times. But stone-waste dumps at mine heads and workshops are causing environmental problems.

Boulders Stone Stones Beach

Stones are broken or crushed from larger stocks for many purposes like roads, embankments etc. which is an avoidable practice. Stones like gravel and boulders (from river beds and old glaciers’ paths) are some of the toughest stones, left over after natures’ processes. But these rounded stones are not used in masonry work, or broken down to smaller sizes. River and seacoast sands are becoming scarce in supply, and could easily be replaced with ground stone, at least in mass concrete plants.

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INDUSTRIAL AGE BUILDING TECHNOLOGY

Post 675 –by Gautam Shah

Industrial Building

Industrial age, from the late 18th C changed the materials of construction and processes. These affected the form, scale and functions of the buildings. Cast-iron, wrought-iron and mild steel were being produced economically and qualitatively. Portland Cement was developed in 1824. First applications of new materials were through older processes, so the change was not noticeable, but did saw the termination of Revival styles. Steel was no longer a stronger cousin of cast or wrought iron. It began to be exploited for its tensile potential. Concrete as Steel-Cement composite offered radically different possibilities.

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Powerloom_weaving_in_1835

New Iron Age

New structural configurations emerged for entities like railroads, depots, shopping centres, bridges, warehouses, factories and commercial complexes. During 1850 to 1870 building facades of steel and glass virtually eliminated the masonry walls. This was accompanied with changes in of the fuels for home warming, cooking and lighting. The glass fronted buildings created new architectural exteriors and brightly lit interiors. Buildings now had deeper spaces, and larger footprints.

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The glazing for openings was larger, and mullions and transoms became thinner or disappeared. The conspicuous columns and beams on the facades began to recede to the interiors. Factories produced opening systems for commercial spaces, now had standard of sizes, shapes, materials and hardware. These also helped the demand for cheap and quick public housing.

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Many older types of openings, typically conservatories, jalousie, bay and bow windows were redefined with better technologies. Till now dwellings, had main facades as a style treatment, and other sides were simpler and less expensive. High rise buildings in dense urban areas were, however, seen from all sides and required equal treatments. The equal treatment on all sides did not respect the climatic orientation or follow the functions inside. The openings’ systems were required to do many different things, depending on the location. Such localization and customization were done by installing new internal treatments to openings.

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Flooring was another changed entity. It was not possible to procure natural materials for very extensive spaces. So many new cement-based systems, precast and cast-in-situ, were innovated.

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The transition to new age was not smooth. The resistance included, rejection of time tested styling and skepticism for new things. These were arising due to several facts, machine-craftsmanship was poor, no quality-assurance was available, and mass-produced items lacked the personalization or exclusivity. At another, level the resistance was coming from designers’ and builders’, who found their roles changing with ready to use components.

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PERSONAL AND BUILDING SAFETY –a List + Links to Blogs

Post 658 -by Gautam Shah

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Detectable_Warnings

ANTI-LIGATURE –Issues for Design -8 https://interiordesignassist.wordpress.com/2016/06/28/anti-ligature-issues-for-design-8/

ANTI-LIGATURE https://interiordesignassist.wordpress.com/2014/04/04/anti-ligature/

SAFETY ASPECTS of DESIGN https://interiordesignassist.wordpress.com/2016/04/15/safety-aspects-of-design/

Penhaligon_Burlington_Arcade_2431

SECURITY in BUILDINGS https://interiordesignassist.wordpress.com/2015/01/05/security-in-buildings/

DOOR SECURITY https://interiordesignassist.wordpress.com/2014/07/13/door-security/

SPACE PLANNING and NON VISUAL CUES https://interiordesignassist.wordpress.com/2015/04/17/space-planning-and-non-visual-cues/

MANAGING the RISKS https://interiordesignassist.wordpress.com/2014/11/03/managing-the-risks/ 

Risk on Brinks

DE-WINDOWING http://talking-interior-design.blogspot.in/2016/11/de-windowing.html

FENCES https://interiordesignassist.wordpress.com/2014/08/28/fences/

GUARD RAILS https://interiordesignassist.wordpress.com/2015/04/08/guardrails/

COMPONENTS of RAILINGS https://interiordesignassist.wordpress.com/2015/05/04/components-of-railings/

RAILINGS AND PARAPETS https://interiordesignassist.wordpress.com/2015/01/12/railings-and-parapets/

GRILLS https://interiordesignassist.wordpress.com/2014/09/30/grills/

TYPES of BARRIERS https://interiordesignassist.wordpress.com/2016/01/07/types-of-barriers/

MANAGING the RISKS https://interiordesignassist.wordpress.com/2014/11/03/managing-the-risks/

ECONOMICS of RISKS https://interiordesignassist.wordpress.com/2014/11/10/economics-of-risks/

Door of a traditional Indian House

Sheth ni Pol Ahmedabad --a gated community

City Gate Prem Darwaja Ahmedabad

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WORK PROCESSES -simplified overview

Post 657 -by Gautam Shah

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Workshops till middle age were craftspeople oriented. A crafts person would occupy a place surrounded by tools and equipments and carry out the ‘Lot’ of work. After that another person took over that lot. For heavy duty jobs mechanical power drives were superior, but one had to shift around to use them. Mechanical devices like gears, leather belt transmission and offered greater productivity. Some degree of task assignment offered standardized products on a massive scale. The power shaft forced organization of workshops on linearity. The line production methods promoted productivity through time management and sequencing of task procedures. In many instances tasks began to be assimilated and handled simultaneously by many crafts-persons in a single time slot.

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power shaft pulley beltsDuring the early part of the 20th C. machines became adjuncts to assembly-line production systems and multi tasking. For this machine became a device to handle a variety of tools, often simultaneously. The machines were operating at a faster speed requiring equally fast control system.

595px-Machine_shop_in_the_Government_Printing_OfficeMechanical power transmission systems were concurrent systems for the entire workshop, but this impediment was removed with the electric power. Electrical power offered local control through an electric motor through horse power rating, speed variation through voltage control and gears, and operational control like start-stop, etc. Independent electric powered machines with faster and multi tasking capabilities, however, were now difficult for human supervision. Control devices were actuators, for process regulation.

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Control devices or systems are of two types: A Feed-forward system has inputs or predicts unusual happening, but would not oversee or govern the actualization of the action. A Feedback system improvises strategy for future actions in many instances oversees actions being taken.

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Feed-forward systems: Jacquard weaving loom uses a feed-forward control as a programmed punched card to weave a pattern, but cannot stop the loom if there is a short feed of thread. Similarly a cutting machine cuts a large sized shape by moving the cutter tracing a small scale pattern through the arm of a pantograph.

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Feedback systems: A wind mill keeps facing the wind with the help of a tail wane. A pressure cooker seals itself with heightened internal pressure of steam. Pressure valves are weight calibrated opening themselves at certain pressure levels only.

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Control devices and systems have led to automation of processes. Automation began in the late 1940s with the development of the mechanical devices for moving and positioning objects on a production line, though observation and manual intervention were necessary. During 1960s digital computers began to offer control systems in three different manners: For supervisory or optimizing control, Direct digital control, and Hierarchy control. In the first instance, for the supervisory control a computer sets parametric levels for optimizing the operations. In the second instance, for the direct-digital control, several devices feed data to a single processor, which then decides a strategy of operation. The advantage here is very fast and objective evaluation of the data. The third system the hierarchy control applies to all the plant-control situations concurrently, often with the actuation of the control mechanisms.

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BLOGS LINKS about PERCEPTION

Post 652 -by Gautam Shah

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These are my select few 91+ blogs (out of nearly 850 placed on my 4 blog sites) written over last 4 years, now compiled under a common theme ‘Space Perception’ with following sub sections.

      0  New series of Lectures (Four) on Perception

  1. SPACE PERCEPTION
  2. ILLUMINATION
  3. MOVEMENT, BALANCE
  4. OPENINGS SYSTEMS
  5. GLASS
  6. GRILLS, TRELLIS, CURTAINS
  7. SOUND and NON VISUAL
  8. OBJECTS, SURFACES, COLOURS, PATTERNS
  9. REALITY, MAKE-BELIEVE

 

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0  New series of Lectures (Four) on Perception

0.1 SOME SOUND BITES -Space Perception -I

https://designacademics.wordpress.com/2018/02/12/some-sound-bites-space-perception-i/

0.2 STRATIFICATION of VISION

https://designacademics.wordpress.com/2018/03/02/stratification-of-vision0.2 /

0.3 PERCEPTION of SPATIAL FIELDS -ILLUMINATION

https://designacademics.wordpress.com/2018/03/11/perception-of-spatial-fields-illumination/

0.4 MULTI NODAL PERCEPTIONS of OBJECTS in SPACE

https://designacademics.wordpress.com/2018/05/14/multi-nodal-perceptions-of-objects-in-space/

 

 

1 SPACE PERCEPTION

1.1 PROCESS of PERCEPTION

1.2 PROCESS of PERCEPTION part-I

1.3 SPACE PERCEPTION -through seeing, hearing and touching

1.4 SPACE PERCEPTION – Issues for Design -4

1.5 SPACE PERCEPTION

1.6 SPATIAL DEFINITIONS

1.7 SENSING OBJECTS BEYOND THEIR SIZE MEASURES

1.8 SPATIAL DEFINITIONS

1.9 SPATIAL DISTANCING and BEHAVIOUR

1.10 DISTANCING in SPACE

1.11 SPACES SIZES and SHAPES

1.12 SMALL SPACES and LARGE SPACES

1.13 REACH in SPACE

Scaffold Building Manhattan New York City Taxi

2 ILLUMINATION

2.1 CONTRAST EFFECT – PERCEPTION

2.2 PERCEPTION of SPATIAL FIELDS -ILLUMINATION

2.3 DAYLIGHTING

2.4 DAY-LIGHTING – in Interior Spaces

2.5 DESIGN CONSIDERATIONS for DAYLIGHTING

2.6 SPACE PERCEPTION and ILLUMINATION

2.7 DAYTIME INTERIOR ILLUMINATION -REALITY and PERCEPTION

2.8 INTERIOR ILLUMINATION through DOORS

2.9 WINDOW LOCATION and NATURAL LIGHTING

2.10 LE CORBUSIER and ILLUMINATION

2.11 COMPARING WINDOWS of FLW, LC and Mies

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3 MOVEMENT, BALANCE

3.1 MOVEMENT and BALANCE – Issues for Design -5

3.2 PERCEPTION of BALANCE and MOVEMENT

3.3 BALANCE in DESIGN – Part 1

3.4 BALANCE in DESIGN – Part 2

3.5 VISUAL PERCEPTION of MOVEMENTS

3.6 PERCEPTION through SCALES and CONVERSIONS -Issues or Design -3 

Landscape

4 OPENINGS SYSTEMS

4.1 LEVELS of OPENINGS

4.2 DESIGNING OPENINGS

4.3 CLASSICAL WINDOW FORMS

4.4 ARCHITECTURAL WINDOWS and VISION in-out

4.5 ARCHITECTURAL WINDOWS and the MEANING

4.6 ARCHITECTURAL WINDOWS and MECHANICS of VISION

4.7 MEANING of a WINDOW SILL

4.8 THIRD DIMENSION of OPENINGS

4.9 LANTERNS in ARCHITECTURE

4.10 CLERESTORY OPENINGS

4.11 SKY LIGHTS

4.12 ROOF LIGHTS

4.13 SHOP WINDOWS

4.14 SHOP WINDOWS – SHOP FRONTS – DISPLAY WINDOWS

4.15 FRAMING of OPENINGS

4.16 MASKING of OPENINGS Part -III -Framing

4.17 MASKING of OPENINGS Part -II

4.18 MASKING of OPENINGS Part -I

Eating_Alone

5 GLASS

5.1 GLASS in ARCHITECTURE -1

5.2 GLASS and PERCEPTION

5.3 GLASS in WINDOWS – Part • I

5.4 GLASS in WINDOWS – Part • II

5.5 COLOURED GLASS

Fixing Metallic Transparency Glass Front Metal6 GRILLS, TRELLIS, CURTAINS

6.1 CONTEXT -Issues for Design -12

6.2 ROOFS 3 -Skyline and Silhouette

6.3 HOLISM and DESIGN

6.4 TRELLIS

6.5 GRILLS

6.6 CURTAINS

6.7 TRANSLUCENCY for CURTAINS

6.8 SHEER FABRICS and CURTAINS

6.9 SHEER FABRICS and CURTAINS-2

6.10 NON SILK SHEER FABRICS and CURTAINS

6.11 WEIGHT and TRANSLUCENCY of fabrics for curtains

6.12 SHEER FABRICS

Religious Kneeling Worship Pray Prayer Church

7 SOUND and NON VISUAL

7.1 SOUND

7.2 SOUND, SPACE and PERCEPTION

7.3 PERCEPTION of SOUND and SPACES

7.4 SPACE and SOUND REVERBERATION

7.5 SOUND and NOISE MANAGEMENT

7.6 HEARING and interior spaces

7.7 ACOUSTICS in SMALL SPACES

7.8 SOUND and SMALL SPACES

7.9 SPACE PLANNING and NON VISUAL CUES

7.10 NON VISUAL LANGUAGE -Issues for Design -6

7.11 LANGUAGE EXPRESSION and SOUND PERCEPTION

wuzhen-1643267_6408 OBJECTS, SURFACES, COLOURS, PATTERNS

8.1 OBJECTS in SPATIAL FIELDS -Issues for Design -14

8.2 COLOURS -Perception and Expression

8.3 COLOURS and BUILDINGS

8.4 FLOORINGS

8.5 FLOORING COLOUR

8.6 FLOORINGS IN INTERIOR SPACES

8.7 PERCEPTION of SURFACE FINISHES

8.8 GLOSS

8.9 TEXTURES and MATERIALS

8.10 JOINTS in SURFACE FINISHES

8.11 MOSAICS

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9 REALITY, MAKE-BELIEVE

9.1 SOLIDS and VOIDS -issues for Design -13

9.2 AUGMENTED REALITY

9.3 SPACES and REALITY

9.4 MAKE-BELIEVE in INTERIOR DESIGN

 

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MEANING of CRAFTS -5 -TOOLS

Post 651 -by Gautam Shah

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Tools are implements used by a person in manual operations for production or processing, like manipulation materials, craft-work, building construction, cultivation, food processing, offense-defence, handling, carriage, measurement and expression (writing, drawing, enacting). Tools have been used for making better tools. Tools are for doings things in an easier manner, as well as for doings things that otherwise would not have been possible by hands. There are few conditions where instead of the tools, the supports and other facilitatory structures and arrangements help in creative efforts and productivity.

Stone Age Caveman Ancestor Hunting Neanderthal

Tools are universal implements, used over different tasks and materials. Over a time, though, an exclusive manner of handling develops. The manner of handling evolves a holding mechanism. The holding mechanism, an entity integral with the tool, allowed efficient use of the tool. The combination of a tool and its handling mechanism was a task (and material) specific facility. The tools and handling section, each served different purposes, and so were shaped accordingly. Both faced different stresses and required different composition. But a combination of diverse forms and materials need to be compatible, coordinated and well joined.

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Handled tools extend and modify the reach of the body. The extended reach helps remote access, adds to leverage and allows torque or twisting. For cutting, breaking, beating, copping and such other jobs need leverage for impact or percussive forces.

Stone Age Tomahawk Blue Archaic Close Hoe Sky

A lever amplifies an input force to provide a greater output force. The lever arm is defined as the perpendicular distance from the axis of rotation to the line of action of the force.

Recognizing objects that can work more efficiently was the first craft. Refining by reshaping natural objects for a specific purpose has been one of the oldest craft industries. Some of the basic craft tools were for food preparation, and personal safety and security. Early tools were fragile and often got consumed in the use-processes. And so, the search for new tools was everlasting, alternatively new tools had to be fashioned from old ones. Redefining the tools necessitated search for better materials, sharpening the edge, and tying a handle.

640px-Adzes_from_New_GuineaTools were now of three basic classes: hand-held tools, percussive tools and projectiles. Other sub-classes were like cutting, scrapping, hole making, vessels, holding, measuring, coating-spreading, digging, mixing, etc.

Haljesta

Primary tool materials were stones, woods, bones, clays and perhaps metals. Some of these could be re-formed by downsizing. Clay and metals were plastic materials that could be re-formed by moulding and additive process.

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Holding tools became important for two main purposes, to hold fine-sized objects and tools and to hold fire or hot things. Fine items like beads, and precious-stones need to be held properly to work upon them. Tool bits like fine and fragile edges need support, whereas fine points for drilling and engravings require adequate gripping. Tools were required to initiate, and work with fire. These included fire-fuel management utilities (chulhas), air blowers, handle for hot tools and holders for vessels. Agriculture related tools like thresher boards, winnowing baskets, sieves, land tillers, etc. Spinning, knitting, and weaving utilities developed for threads and cordage, which were used for binding handles, roof and wall elements, fishing nets, etc.

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Tools, as said earlier, are handy things. But there are many utilities, facilitatory structures and arrangements that have helped creative efforts and productivity. In these, at certain level of detail tools like appendages or similar advantages are invested. One of the first ones was the fireplace that contained the fire, helped efficient use of the fuel and offered resting stands for things to be heated. Similarly structures were created as dwelling spaces, clothes or apparel, shoes, head caps, adornments, toys, totems, murals, shutter systems over openings, hangers for food to protect it from insects and rodents, sleeping mats, hammocks and cradles, lamps that evolved less heat but more light, food grinding stones, narrow neck pitchers for liquid storage, slide for transporting goods, etc.

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At some level the tools, utilities, facilitatory structures and arrangements were merged as devices, machines, apparatuses, equipments or plants. These were integrated with the built-forms, for support, location-based advantage or task setting. The tool, craft and technology were one seamless pursuit. The pursuit also integrated several materials into not only single purpose entities but very specialized task facilities. The task related specializations also created technology-based castes, guilds and communities. The craft communities are tied to terrains and climates. This allows them to develop acutely ethnic styles.

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PASSIVE VENTILATION in Buildings

Post 648 -Gautam Shah

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Passive ventilation sustains good quality of air in interior spaces. It works on circulation or movement of air without the use of power utilities. It relies on principals of source management and dilution, rather than any filtration. Passive ventilation is substantially based on the quality of built-form and to a smaller extent on immediate surroundings. It is a very important method of adjusting heat and moisture in Hot-arid and Hot-humid climates. The quality of air is determined by temperature, moisture content, presence and proportion of ‘other’ gases and airborne particulate matter. The quality of air has important bearing on our body. A body may endure or adopt to certain abnormal conditions for a period of time but there may occur side effects. The side effects may be realized in a different form and at a different time.

640px-Krishnapuram_durbar

Passive ventilation relies, as much on external or macro conditions, as the interior spatial lay. It is based on three factors:

  1. Air movements due to the differing pressures and temperatures and the buoyancy forces that result across a building and its surroundings,
  2. Location of tasks and activities that support or hinder such patterns of air movements, circumstantial and designed apertures in the building shell.
  3. Factors that define the ventilation in a building are, space-profile (section), base levels of inward-outward nodes of ventilation, nature of surroundings and neighbourhood, sill level, depth and its profile-shape, task-intensive operative plane and its volume, and constraints enforced by elements such as size and shape of external overhangs.

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Passive ventilation occurs with Two major operants.

Differential air pressures are formed by wind movements in the immediacy of the building, the pattern and size of the buildings scheme and individual components of the building. Air movement also occur as a buoyancy effect caused by the temperatures of surfaces and surroundings near the wind-ward and wind-off sides. Air pressure difference occurs, across buildings’ interiors and exteriors, across the openings and temperature of surfaces and surroundings, near the windward and wind-off sides. Entry and exit point for air, though continually shift around due to the changes in pressures.

Desert City Oasis Town Ait Ben Haddou Oasis

Temperature differential depends on the direction and inclination of sun, climate, seasons of the year, local massing of the shadows, surface materials, vegetation, water bodies, and presence of heat evolving entities. Dark surfaces and thin body objects warm up very fast and begin to radiate the heat, creating local heat related buoyancy in air.

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Ventilation requirements vary depending on whether one wants to gain or lose heat, add or subtract moisture, dilute or remove ‘other’ gases and airborne particulate matter contaminants. Ventilation needs change depending on, distance of space occupation from the inlet-outlet for air, functional use of space, types of tasks, work-schedules, crowding in the space and presence of heat evolving means (hearths, machines, etc.). One important aspect is the feeling of air movement near-over the body. It depends on several factors such as air velocity, fluctuations in air velocity, temperature of air, and personal factors like overall thermal sensation and activity level. Even for the same person, sensitivity to air movement may change from day to day.

635px-Wall_Decoration_at_Kesava_Temple_in_Somanathapura_retouchedDraughts (Draft) are very low velocity air movements. These are not always perceptible, as they do not cause any sensation of pain or pressure on skin. Draughts are more felt due to air pressure thresholds near cracks and such leakage points in small and enclosed spaces. Draughts, however, help in convective heat exchange, evaporation and dilution of pollutants in air. Draughts cause localized cooling or heating of sensitive organs of our body.

Breeze or low to medium velocity air movements generally affect only local areas. Breeze does not let airborne particulate matter to settle down. Skin sensation can be avoided by appropriate screening and deflection of the breeze. Since breeze causes effective pressure on skin, with very immediate and very perceptible change sensation.

Winds are high air velocity movements of air affecting larger regions. Winds raise particulate matter in the air, cause rapid change in level of humidity and often cause discomfort due to high pressure sensation on the skin.

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In hot and cold both types of climates people often close all the openings to reduce the air movements and thereby control the convective heat gain or loss. Turbulent air velocity is less comfortable than a Laminar air velocity. Turbulent air movement achieves a better mix of air whereas laminar helps in greater displacement of air mass. This is the reason why in hot arid climates small size openings are used to create turbulence or a viscous flow, and in hot humid climates the body level openings of horizontal nature create a laminar flow to displace the humidity.

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Passive ventilation occurs through macro and micro openings. Macro or formal openings (doors, windows, gaps etc.) are designed with a characteristic size, shape, passage section, adjunct elements on internal and external faces, and occur close to the location of need (for ventilation). Micro openings are circumstantial, and are much smaller in size like cracks, crevices, gaps or apertures. Micro openings offer a passive and consistent ways of managing comfort in enclosed and semi-open spaces. These manifest as intentional gaps, unplanned crevices and cracks of structural stresses. Both, macro and micro openings can be broadly be classified by their locations.

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  • Roof level openings are such as in the thatched and country tile roofs, loosely laid roof slates, stone sheets, or intentionally placed micro passive vents such as lattices, chutes, hoppers, etc.
  • Upper section openings in walls are such as the unpacked ends of corrugated sheets or roofing tiles, ends of purlins and truss and eyelets or oculi like holes and lites in gables.
  • Other openings manifest as doors, windows, cut-outs, chowks, in joinery, leaky fitments, ajar shutters, door bottom space, peep-holes, latticed constructions such as of woven mats or fabrics, louvered openings, crack or fissures in building elements, expansion joints, unsealed joints, etc.

Movement of air through openings encourages evaporation and increases cooling in the interior space. In dry arid climates dwellers locate their activities in the strongly directional air movement formed by small and deep-set openings. Deep-set openings also increase absorption of heat in the mass of the structure. Simple passive cooling devices such as water wetted grass mats or fountains help cooling. Outside air has lesser moisture (except during raining conditions) then indoor air, so any level of ventilation, dilutes the interior humidity level and adds to the comfort.

620px-AlfedPalmersmokestacksAir borne particulates arrive from outside sources like heavy vehicular traffic, polluting industry (mines, thermal power plants, mineral grinding plants, in the vicinity, or sand storms, and internal sources like cooking or craft fuels, and processing materials (grinding, spinning-weaving). Outside particulate can be controlled by changing the ventilation gaps to different location or elevation. Filtration screens occupy more then 60% of opening area, and much lesser due to frequent choking. Dynamic screening like water bodies or sprays can be useful, but costly and perhaps beyond the concept of a passive device. Non turbulent wind flow helps in keeping the particulate matter to lower sections.

Moisture control in interior space occurs by dilution, greater air movement and siting management of moisture generating amenities. Isolation of cooking, washing, bathing areas in dwelling is a common practice in hot-humid climates.

Quality of indoor air mainly depends on the external circumstances. The ‘feel-good aspect’ in a tropical climate (hot-arid or hot-humid) zone is not only regulated by the obvious temperature, rates of movement (pressure) and the moisture content, but also by the level of fouling of air. Some experts have claimed that air quality of a room is chiefly determined by its CO2 concentration. In tropical buildings concentration of CO2 and other gases is not a critical factor, as numerous openings and micro gaps remain substantially open. Location of cooking area is a segregated entity or an outdoor activity, and like cold climates no interior fire places.

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