Thursday, December 26, 2013

RAMPS as Transfer Systems in Buildings


Ramps are inclined pedestrian passages without vertical risers and have a pitch lower than stairs. Ramps are easier to ascend or descend than stairs, but occupy more floor space. Ramps when steeper than 10 %, require a non slip flooring and a grip-able handrail. Ideal pitch for a ramp is below 8.33 % (1:12), however most codes accept pitches up to 16.66 %. For short run such as 5mts. Some labour laws allow 25 % pitch for very short runs (2mts) such as for ware house and factory entrances, but only for ascent. 10 % pitch is a very common provision in building design. Ramps for wheel chair users should not be steeper than 5 % (1:20). Length must not be more than 6 mts in passage length, and landings or rests should be at least 1650 long. Casual ramps or slopes in parks and landscaped areas nominally follow the angle of repose of the soil, but if these are to be used as passage ways, the pitch must not be greater than 8 %.

Width requirements: for single lane traffic 750mm, furniture passage 900mm, for cinema hall interior mid seat aisles minimum 1200mm, increasing 70mm in width for every 1mt of passage run.

Straight line layout of multiple ramps
must be avoided. If inevitable it should for 2 passage laps only. Secondary units of the ramp at right angle or U turn are advisable. For normal users ramp lengths of maximum 25 mts or 2 mts climb per lap are ideal.

Ramps are used in place of stairs or steps. Ramps provide a very smooth transfer between elevations. Wheeled items like trolleys, perambulators, chairs, vehicles are easy to move on ramps than stairs. Ramps require the least energy amongst all movement systems between different elevations. Ramps due to their design, take up a lot of space and require a large structure. Continuous ramps tend to accelerate the movement speed in descent and become hazardous. Circular ramps generate concentric force during rapid descents. Multi-directional ramps require additional elements to cutoff the accelerated speed of descent at the change junctions.

Factors that define the utility of a ramp
are: Texture of the floor, gripping power of the handrail, height of the handrail, distance between two handrails (small width -under 800mm, ramps allow holding of both side rails), configuration of the ramp structure, pitch, movement to ascend/ descend, age profile of the users, orthopaedic functionality of the user, etc. It is very difficult and hazardous to move on a ramp with any head load (railway coolies), as the weight on head raises the centre of gravity of the body. This is the reason why people stoop forward while climbing up steep slopes, and backward while moving down a ramp slope. All ramps in a consecutive usage must be of one consistent pitch. Parabolic, concave or convex curvature pitches are not favoured in buildings.

Ramps have been used for moving materials to construct structures like Pyramids, Ziggurats and Inca temples. Ramps have been used to move heavy guns to fortification tops, to negotiate hills and mountains and to draw water from wells. Ramps have been used as entrance way in many buildings, such as the Ziggurat, Egyptian temple of Queen Hatshepsut, etc. Ramps have been used by Le Corbusier as an indicative of democracy and ceremony (Cultural Centre, Textile mill owners building, Shodhan Villa at  Ahmedabad, India and at the Secretariat building, Chandigarh, India.)

Ramp and stair combination: Ramps are also used along with steps to provide a dual system. However to match the gradient of the ramp, such steps have very wide tread and very low height riser, making them very difficult to use. In hospital areas such steps between or on one or both sides of the ramp help the person to push the chair or trolley up or down the slope with better control. The same configuration is used in industrial warehouses to move large barrels or wheeled items. Ramp and stair combination is also used in inclined elevators. The slope accommodates the rails or the guides of the inclined elevator and the steps are used by the service personnel. Here the gradient is usually very acute so the tread is very narrow while the riser very tall.

Parabolic ramps
are used in places like Amusement parks, water games parks etc. A parabola has two sets of inclinations. The short radius curvature of the parabola, if at the lower end, helps in retarding the speed of descent, while the larger curvature of the parabola, if at the lower part, the initial  acceleration gets a sudden boost at the end. This later version is very hazardous and is used if only sufficient fore space or speed absorption mechanism (sand pit, water pool) is provided for beyond the parabola. Ice skating tournaments where a skater needs very high speed start to accomplish the required twists, turns, lump before landing, have such slopes. Roller coaster rides make extensive use of ramps structures to create very intensive centripetal and centrifugal forces with high accelerated speeds that almost defy the gravity. Cycling stadiums use double curvature ramps. Channelled ramps of water parks use and inward as well as outward curves (clockwise and anti clockwise movements), variety of pitches and parabolic curves (mainly in the end section) to generate sideways thrusts, acceleration and de-acceleration.

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Tuesday, December 24, 2013

CORRIDORS and PASSAGES as Transfer Systems in Buildings

Corridors and passages denote permanent transfer zones in buildings. These are usually well defined and functionally supported by other systems. However, when design definitions are improper, have inaccurate capacities or lose the validity due to the changed circumstances, not only the corridor but all other related systems become ineffective.

Corridors originate at points of transfer like doors, other branch corridors, stairs, elevators etc. Corridors also occur where conditions for superior and efficient transfers are available, such as: shaded or protected areas, finer floorings, smoother gradient, pleasant surroundings, promise of fulfilment, expectancy, escape from hazards.
Straight corridors provide a very efficient mode of transfer, but tend to be monotonous. Straight corridors allow continuous acceleration, which may pose problems to other transferee. Corridors with zigzag or variable movement directions heighten the expectancy. Circular or curved corridors tend to align the movement concentrically. Bidirectional movement corridors increase the social interaction amongst the users. Multi directional and multi velocity movements destroy the character of a corridor.

Corridors are heavy movement areas, so create a lot of noise and transmit pollutants. Corridors often enhance the fire hazards, spread of infections, and security risks; however, if properly designed corridors may curtail such risks. A straight corridor can be policed from one point, but so an intruder can command the entire corridor.

Corridors often have several services attached to them, such as: toilets, drinking water fountains, fire fighting systems, emergency exits, air handling units for air-conditioning systems, electrical mains, bulletin boards, exhibitions, first aids, security check-up systems, food and beverage dispensing systems, signs and graphics. Tirupati temple (India) corridors are also used by devotees as a place to sleep, rest, eat, bathe and pray by the devotees during the long wait for the Darshan.

In complex buildings variety of work spaces each with specific environment and controls are required; corridors help to create an intermediate or equitable zone of transfer for all such connected units. Corridors provide a strong cohesive identity among apparently very unrelated cells.

Corridors or passages defined and bounded by a barricade system only, require a minimum width of 630mm (such as bus stop queue passage) enforcing discipline, or nominally 800mm for one person wide queue. Enclosed corridors or passage, as suggested in most residential building bye-laws, should be minimum 900mm wide for short length runs of 5mts. For greater lengths a width 1200mm is advisable. For wheelchair traffic minimum 1000mm width in straight sections, and more in angles or curvatures, is required. Where movement is likely to be intense, bidirectional and with hand carried luggage a width of minimum 1500mm should be provided. Where corridors are likely to be 1500mm or less in width, the doors should be placed in a recess, and must open away from the corridor space. Preferably doors should not open out into the corridors unless a recess equal to the full swing of a door shutter is provided. Opposite doors on a corridor should be preferably staggered. At all the end, start or junctions, there should be no door opening for a length equal to the width of the corridor. Cross corridor junctions must happen in a wider lobby or foyer. Corridors should have a secondary escape point for every length section beyond 15mts. Very long corridors tend to be boring so should intermittently terminate into a hall or foyer before being continued.

There should not be any projections or fixed or loose furniture in the functional width of the corridor. Where visually impeded people are going to transit, the projection off the wall must not be more than 100mm, and furniture including the space for knee or leg of the user must be accommodated in alcove or niche.

Illumination in corridor needs careful planning. Windows at the end of a corridor, or doors on corridors opening out to an exterior, create a glare. Artificial compensative illumination is very necessary to counter the glare. Openings on the sides of a corridor provide a visual distraction, but unless fairly intermittent or properly designed, create a very patchy lighting. Wall mount illumination fixtures and ceiling spots fail to provide the desired effect when corridor height is low and traffic density high. Illuminated ceilings provide very poor modelling and social recognition. In such situations lighter colour scheme and indirect glow not only on ceiling but  upper section of the side walls helps. Illuminated steps and side hand rails provide a functional definition. Illumination level in corridors should never be consistent as it creates boredom, It should be high enough near openings to counter the glare and in some situations (drama auditorium) even feeble in contrast to the interior. Illumination fixtures that are visible like shaded lamps, diffusers, chandeliers etc. create a visible physical dimension.

Paintings on corridor side walls
must be smaller and with greater details that can be enjoyed at a closer distance (often less then 450mm) such as Indian miniature paintings. Large paintings with very extensive colour or form patches are hardly visible in a corridor like narrow space. Passages, (unbounded corridors) require side edge definitions. Such definitions could be in terms change in flooring colour, texture or pattern if the traffic density is low. Alternatively definitions could be through change in the floor level or side barricading at 800mm to 1200mm level. The barricades could be ceremonial or representative only. The barricades could also be intermittent like planters, boxes, ash-posts, poles, etc.

Passage and corridors carry services such as ducts, wires, etc. To manage these often a cover like a ceiling is required. The ceiling is designed to absorb the locally generated sound, and also mask the sounds that leak  out from the rooms, through the crevices along the installed services.

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Monday, December 23, 2013

TRANSFER SYSTEMS in buildings

Transfer systems denote routes or spaces where concentrated movement of people and goods occur. Stairs, ramps, elevators, escalators, corridors, passages, bridges, etc. are elements or systems that can be collectively identified as transfer systems.  The transfer system denotes an exclusive one or the most efficient node available leading to a concentration of traffic. The intensification of traffic is inherent due to the locational advantage or is generated by specific design.

Transfer systems are perpendicular (vertical), inclined against or towards the gravity and parallel (horizontal) to the earth. Stairs, Elevators and Escalators are movement systems, where goods and persons transfer perpendicular to the gravity. Whereas Corridors, Roads, Auto-walkways are movement systems that are almost parallel to the gravity. These of course by design allow greater concentration of traffic compared to many other parallel to gravity areas like chowks, compounds, halls etc.

All movements are essentially directional. An  unidirectional system is more efficient than any bidirectional or multi-directional (mixed) movement systems. Hypothetically all transfer systems are bidirectional. It is not necessary for the reverse transfer system to occur in the same time and space. However, when there are too many multi-directional movements within a given time and space frame, a clear identity of a transfer system is not perceptible. Within such chaos ultimately all movements cease.

 Transfer systems occur as:
  • point to point (direct system)   
  •  one point to many points (divergent system)    
  • many points to one point (convergent system) 
  • many points to many points (chaotic situation)

Transfer systems are either, open-ended or looped. Open-ended systems have a finite start-point and a termination point. Start-point is one where the first transferee element gets on the transfer system. The end point is one where the last of the transferee element gets off. It is also a point where another system such as the reverse, or parallel movement system begins. Looped systems are continuous systems and have no start-points or terminal points.

The intensity of transfer depends on whether the system operates continuously or intermittently. Continuous systems such as the  escalators, automated walkways, are governed by the speed of movement, while the intermittent systems such as the elevators, buses, railways are affected by the frequency of movement’s module. Both systems however have a traffic capacity limitation.


The efficiency of a transfer system is determined by the fact whether the system is parallel, inclined or perpendicular to the gravity. The additional effort required to work against or towards the gravity, respectively retard or add to the efficiency.

In a transfer system, people move depending on two counts,  anthropometric design of the system, and orthopaedic functionality of the transferee. On the hand vehicles or goods modules are carried by use of external energy through mechanical devices. Variable capacities of the transferee also affect the speed of transfer, and as a result the intensity of traffic.

 Transfer systems are disturbed when elements moving at different pace cause an unwanted change in the speed or direction of the general moving mass. Transfer systems become invalid when all goods and people reach their destinations, or when there is nothing left to transfer.

Transfer systems necessarily have start-end nodes, but most transfer systems have multiple exit and entry nodes or points of transfer on the route. Some points of transfer are very clearly defined, like a door in a corridor, railway station, but many others are not clearly delineated such as path or footpath without a barricade. Transfer systems that are exclusively directional, with high speed or of mixed traffic, require highly defined points of transfer.  At every point of transfer goods and people have to alter the direction and change the speed of movement to embark or disembark the transfer system. Such variations in movements at every entry or exit node reduce the overall efficiency of a transfer system, unless points of transfer provide necessary definitions. Points of transfer provide visual and other information about the available options. A subsidiary system often allows a slow-moving transferee to gain required speed and direction before moving over to the fast-moving main system.


Straight transfer systems have greater efficiency, than any sharp twisting turning system. Transfer systems directed towards gravity or any superior environment such as towards promising - enticing situations tend to have greater efficiency. Point to point systems are superior to continuous systems with many points of transfer on the route. Transfer system with designed points of transfer operate better.

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Tuesday, December 17, 2013

Projected Opening Systems in Buildings



PROJECTED OPENINGS SYSTEMS in BUILDINGS:  Opening Systems have transgressed the nominal edge of the architectural form. Such outward, and occasionally the inward push occur on the wall faces, roofs, corners and floors. Examples of forms of wall face transgressions are: Oriel, Bay-window, Bow-window, Zarokha and Mashrabiya. Some of the important reasons are: Emphatic architectural expression, Enlargement of the interior space, Greater opening size (for wider view illumination, solar gain, and aeration), and Facility to have sideways view.
 
ORIEL:

Maison des Quakers Belgium

Bay Window Maison Pfister Colmar

Oriel windows are a form of polygonal bay windows. Oriel windows have a larger perimeter and so allow wider view of the outside. Oriel windows increase the floor space without increasing the footprint (extent) of the building. Oriel windows are usually placed on the upper floors of the building, but siting on ground floors is not uncommon. The windows are projected bays, supported off the base-wall by columns, piers, corbels or brackets.
  • The word oriel is derived from Anglo-Norman oriell and post-classical Latin oriolum, both meaning gallery or porch, perhaps from classical Latin aulaeum, curtain.
Oriels have of many forms: Sill is at the floor level, seat level or mid body level, the head-side of the projected gap terminates at lower position, such as at human head level or reach to the ceiling level of the room. Some oriels are partly or wholly glazed and are known as oriel windows, latticed forms are found in Indian Zarokha and in mid East or Arab architecture as Mashrabiya. In both the cases the lattice reduces the glare and provides privacy. Zarokha is more commonly made of stone work, and Mashrabiya have carved wood latticework and often stained glass.

Oriels developed in the 15th C, when under the Tudor kings peace prevailed in England, Wales and Ireland. The prosperity of the great landowners, aristocracy and  Church supported new constructions. Though Italy was seeing revival of classical architecture, Tudor style was mainly local. Merchants and artisans, generally living over the shop in a narrow and tightly-packed town houses, added space by building storeys. The upper storeys were projected out over the street. This encroachments often resulted in extremely dark streets. Timber-framing despite the fire risk, was popular. Oriel windows were also placed over gateways or entrances to manor houses and public buildings. Oriel windows once again became popular during the revival of Tudor style in the 19th and early 20th C, and during Gothic revival (1740).

BAY WINDOWS:

Bay Window
Carved balcony, Mehrangarh Fort, Rajasthan, India

A bay window is an exterior projection of room space, forming a bay of square or polygonal shape. The round (segmental) shaped windows are called bow-windows. Bay windows became popular with Victorian architecture (1870's). A typical bay window consists of three windows, the middle unit is parallel to the house and adjoining two units are set at 30 to 45 degree angles. Bay windows are created: to increase the illumination, provide a wider view of the outside and enlarge the interior space. The bay windows are used on sunny sides in colder climates, over sections facing road side, garden and other natural scape.There are three basic types of bay windows. In full bay windows the opening stretches from floor to ceiling level to create a nook in a room. In half or part bay window, the window starts at seat or nominal sill level and reaches head height level or full ceiling level. In the third version the bay is more of a flower box projecting out. The nook created by the full bay window is well illuminated and has better view of outside so it is used as study area, breakfast space, solarium, hobby area, etc. For these purposes the inner ledge of the bay window is used as built-in seat.

  • The building act of 1707 in London and other towns of England did not allow projections on a roadside, to prevent spread of fire along the wall. This was changed in 1894 so that windows were not required to be flush with the exterior wall. During the Victorian and Edwardian period houses began to have bay windows.

BOW WINDOWS:

 Groothaert Boulevard De Smet de Nayer Bow Window

A bow window, is a curved or polygonal bay window. Unlike the bay window, there is no middle window unit, parallel to the room. Instead several small width window units (fixed and shuttered) are joined to form a bow shape. Bow windows first appeared in the 18th C in England and in the Federal period in the USA. Bow windows are also called compass window and radial bay windows.

ZAROKHA or VIEW-BAITHAK (seat) WINDOW:

Adalaj Stepwell, Ahmedabad, India

A Zarokha or Baithak (seat) is a raised platform than the room floor. The raised Zarokha has one facing opening same or slightly larger then the gap in the wall. Adjacent to this, at right angles are two smaller openings. Zarokha has short height tapering parapet, and two small height columns.  The projecting platform and the can accommodate two or more people. The wall gap or the top of the tapered parapet was covered with a lattice of Bamboo, wood, metal or stone.  The Zarokha is an ornamental element that was well placed in the architectural composition.

The Zarokha originated from the Gokh or Gavaksh (Sanskrit), a form of articulated wall niche for storage. It became more of an opening or  window form. It was placed on exterior side of building facing garden, estate, or busy street. During 8th and 11th C AD., during the peak of Hindu architecture, it reached its classical prime. The Zarokha in many ways compensated the need for an intermediate element like verandah in tropical architecture. It created a private domain, accessible from interior compared to a verandah. The Zarokhas covered with a lattice reduced the solar glare and heat gain. Latticed balconies were readily adopted by the conservative Mughals and Rajputs to provide privacy for their women folk.

The Zarokha and such window forms were further refined as Chhatri (pavilion) and other roof level facilities. Large openings were appended with half Chhatri form, made up of two delicate columns and a partly pyramidal roof of straight, concave or convex surfaces. Jali (Lattice) as a filler screen was made of sand stones, marbles or wood, carved with  geometric or floral patterns. Jalis were strongly divided by mullions and transoms. Jalis were punctured with small clear openings such as in Hawa Mahal, Jaipur, India. Jalis were primarily used to curtail the glare but were also used to cascade the flowing water from fountain channels to moisturize the air.

MASHRABIYA:

Mashrabiya is a projected window on second or higher floor, in buildings mainly the urban setting. Mashrabiya are used in houses and palaces although sometimes in public buildings such as hospitals, inns, schools and government buildings. It is commonly placed on the street side, but occasionally on the internal courtyard 'sahn' side. Mashrabiya windows are presumed to have evolved during 12th C in Baghdad. Iraq and Egypt are two countries where many examples survive. They are more common in Eastern (mashriq) parts of the Arab world then the western (maghrib) parts. Basra is often called the city with Mashrabiya. It was introduced in France from its colonial sources, and called moucharabieh.

Mashrabiyas are enclosed with carved wood latticework, composed of the lathe turned wooden sections (bobbins), in complex patterns. Smaller lattice openings in the lower section obscure vision from outside and reduce the air draft, whereas larger openings in the upper parts allow better air draft and illumination. Lattice design differs from region to region.

Mid part of the Mashrabiya is provided with sliding or a side-hung shutter for a clear opening. Mashrabiyas are also lined with stained glass to form an enclosed balcony, and an independent space attached to a room. Shanashil is net or wood screen-covered verandah or porch over looking a street or garden. Mashrabiya in farm houses and for out of the town buildings are more open, with reduced amounts of lattice work and without the lining of glass. Egyptian Mashrabiya projects out at a slightly raised level providing for a Dakkah (a Dakkah is a masonry platform attached to the front part of a house, covered with a rug, it is used for informal talk and tea in Arab rural areas, an arrangement similar to Ota or Otla in a traditional Indian house) or in front of the window, similar to the Indian Zarokha.

Mashrabiya adds space to rooms on the upper floor without increasing the foot print area of the building, but these have also been used for correcting the shape of upper floor front room. Mashrabiya allows air from three sides to enter, even if the draught outside was parallel to the house facade, on the other hand it serves the street and in turn the neighbourhood. Mashrabiya also provides shade for the ground floor windows.

  • The word Mashrabiya has varied origins. Mashrabiya denotes drinking or absorbing. The name perhaps has derived from a wood lattice enclosed shelf located near a window to cool the pots of drinking water. The shelf evolved until it became part of the room with a full enclosure. Mashrabiya also has originated from verb Ashrafa =to overlook, ignore  or to observe.

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Wednesday, December 11, 2013

Managing Temperature for Interior Design


Climate conditions our living. We find ways  to survive and conduct tasks in a manner that is easier than ever before. We adopt the climate through instincts, learning, and also have the built in resilience for occasional variations. We get acclimatized to the normal climate of the area. It is through the design of the built-form, exploration of materials and setting of a lifestyle that we achieve a greater degree of adaptability for climate. Through a continuous process of selection and elimination we develop a comprehensive system that is natural for the geographic region. Climate adoption also involves some physiological changes in the short and very long terms.

During early periods attempts to understand the climate were limited to determine the level of its predictability.  For these seasonal changes, rain fall, and temperature variations, were locally recorded and interpreted. The collated data of various regions gave an understanding of the macro climate. This helped in agriculture, migration, and seasonal comfort. Today we have a greater perception of the climate is much broader, with components such: as air currents, pressures, humidity level, solar heat, sea currents etc. We also have better knowledge about how other beings and plants respond to the climate. Study of human endurance in very acute conditions like space shuttles, arctic conditions, deep water diving, undersea explorations, supersonic jet travel, high altitude mountaineering, provide us with a lot of feedback on how to deal with climatic variations.

Climate profile parameters mainly include:

    TEMPERATURE

    HUMIDITY


    AIR MOVEMENT


An effective climate profile of a place and time emerges through comprehensive mix of all these parameters. However, temperature related comfort derives through fine tuning of siting, size, shape, form (openings and other architectural features)  of the building,  time-space scheduling of tasks, lifestyle setting, food and clothing.


TEMPERATURE:
Temperature is the major determinant of comfort level. Air temperature determines the rate at which our body will exchange heat with the atmosphere. Rate of heat exchange also affects the metabolic activity of the body and as a result its work capacity, fatigue and recovery schedule. In a temperature range that is acutely different from the acclimatized one, our body has to work harder to adopt to the situation.

Direct solar radiation is the key factor for heat gain. It heats up various objects, depending on their thermal capacity, conductivity, colour, texture etc. Heated objects radiate this heat, as long wave radiation, back into atmosphere, often after the main source has ceased its input. Such delayed heat releases, create very complex patterns of heat gain or loss. A temperature profile of any space is rarely consistent and this causes different gradients and convective air movements. Such air movements affect the quality of air, rate of ventilation, density of air, rate of evaporation and the level of humidity in a space.

A building is affected by the type and level of energy transfer that takes place with its environment. Energy flows in and out of a building. For a building, the shell (shape. size, materials etc.),  siting, the amenities etc., are more or less constant factors, but the variables are: climatic parameters, inhabitants and tasks. When constants and variables are appropriately matched, we get an environment that is always in a flux, only partly predicable, and often with surprises.

A      Conduction of heat may occur from various types of surfaces, inward or outward,  depending on the temperature gradient. Conduction of heat is affected by the `transmittance factor' of the building materials. It is also affected by the area, colour, opacity and texture of the surface.

B      Solar gain through transparent surfaces is governed by the area, angles of the incidence, quality of the materials.

C      Convective heat exchange takes place with the movement of air (ventilation). This may be due to unintentional infiltration (leakages) or deliberate ventilation. The rate of convection depends on the rate of ventilation (air change), velocity of the convective medium (air), temperature difference and specific heat of the convective medium (air).

D      Internal heat gain in space occurs from the output of human bodies, lamps, gadgets and appliances.

E    Heat removal due to evaporation that occurs in the vicinity, outside and inside the building.

F    Deliberate addition or subtraction of heat by passive and mechanical devices.

The net thermal balance in a building shell is a result of all these factors. From a climate point of view, a building behaves like a biological entity, that is in a continuous process of achieving equilibrium. But the process, towards the equilibrium, is not always favourable to the inhabitants or their activities. We need to hasten, delay, curtail or terminate some of the climate processes. For the purpose primarily we use passive devices. Such devices include shading devices, insulation systems, heat absorption or dissemination systems. However, in a particular time and space frame when it is often not feasible or adequate to control the climatic processes, and we use non-passive (electro-mechanical or chemical) devices.

Designers primarily rely on materials and form of the building to achieve a favourable exchange of energy. Designers also utilize features of the surroundings to modulate the energy exchange. These tools are the site features like slopes, hills, mounds, gorges, valleys; or  landscaping features like pools, plants, shrubs, hedges, groves, etc.

Designers facilitate various activities at specific space sections by locating amenities and facilities. Designers promote and indirectly regulate the time schedules for various activities, making amenities and facilities to be either fixed or relocatable.
  • For macro level perception and comfort planning several temperature zoning methods are used. Some depend on geo-spatial definitions through latitudes, and others depend on regional demarcations. A more practical method is the combined system.
  • Humid tropical zone surrounds the equator 10 N to 10 S. Here mean daily temperatures are 25-27  C, and the diurnal variation exceeds the modest annual variation. Rainfall varies but is generally above 2000 mm per annum. There are no marked `seasons'.
  • Semi arid tropical zone follows the humid tropical zone. Here the seasons are distinctive. Temperature and rainfall reach their maximum in summer months. A dry and slightly milder (colder) season prevails as soon as Sun moves to the other hemisphere.
  • Arid tropical zone is next to the semi tropical zone, around 30 N and 30 S. This is a zone of subsiding air, with limited cloud cover and with sporadic rainfall. There is a high diurnal temperature range, due to high solar gain during day time and high loss during night time with clear skies. Evapotranspiration exceeds the normal precipitation, resulting in a net water deficit.
  • Semi arid sub tropical zone has marked seasonal contrasts. Some variations occur in coastal regions such as in Mediterranean region. Here the subsiding dry air of the tropics predominates in summer, while in winter low pressure brings rain and lowers the temperatures.
  • Temperate humid zone, at 50 N and 50 S are marked by the westerly-easterly winds. Here low pressure cells and polar fronts dominate. The winters are moderately cold, and summers are comparatively cool and rainfall year round. In regions away from the sea, there is snow in winter, and thunderstorm activity in summer. In deep set areas the temperature may reach 40 to 50 C , and are called semi arid temperate zones. In some areas the precipitation is so low that arid steppe climate develops.
  • Boreal zone is closer to the pole regions, where winters are extremely cold and summer or non winter period is strikingly different short, but cool. Day lengths or daylight time zones are very varied. Land is mostly frozen (permafrost) year-round.

HUMIDITY:
Level of Humidity level affects our sense of well being or comfort through the affective range of temperature (actual feel). Perspiration and sweating, the prime mechanisms to dissipate the body heat, depend to an extent on the rate of evaporation. Air with high percentage of humidity is also comparatively deficient in oxygen and may cause problems to people with TB or asthma. Low level of humidity removes the moisture from the nostril, reducing its filtering capacity to keep out the air borne pollutants.

Level of humidity is the amount of vapour held by air at a particular temperature. When there is a rise in temperature, the air expands to accommodate more vapour and inversely with a drop in the temperature, the air density increases can hold a lesser amount of vapour. A reduced level of humidity encourages higher rate of evaporation, which is accompanied by a drop in temperature. Nominally with reduction in temperature the capacity of air to hold the vapour decreases, and beyond certain temperature range the excess vapour  condenses as water droplets.

  • Four distinct humidity-climate zones are recognised.  These are: 1  Hot-Dry (arid), 2 Cold-Dry (polar or glacial), 3 Hot-Wet (dense tropical forests -selva), 4 Moderate-warm to cool-humid (temperate).
In hot and humid climate high level of humidity does not allow adequate heat dissipation through evaporation of the perspiration. As a result body temperature increases and it has to resort to other methods of heat dissipation. In hot arid climates the low level of humidity causes rapid evaporation. Body cannot cope up with such rapid rates of moisture removal as it has limited amounts of water available within it. In cold arid climates the body has no excessive amounts of heat requiring dissipation through high perspiration. However, the low level of humidity removes even the moisture that helps the skin to remain soft and supple. In cold humid climates even minute perspiration does not evaporate readily, and in excessively cold climates it may cause a frost bite.


AIR MOVEMENT: Direction, Velocity and Movement patterns of air, are the three factors that govern the 1. Temperature profile (of human body, surrounding objects and atmosphere), 2. Quality of air (through dilution or change in contents of air) and 3. Rate of evaporation (humidity management).

Air movements occur in consonance with global patterns of air. The air velocity is caused by differential temperatures and pressures. At micro level air movements occur due to the macro changes in the surroundings, movements of people, objects (doors, vehicles etc.), opportunistic shapes and sizes (cones, wages), and air movement devices.

  • High velocity air movements are known as Winds and affect large regions. Winds cause rapid change in level of humidity. It often causes discomfort  due to high pressure sensation over the skin.  Winds raise particulate matter in the air.
  • Low to medium velocity air movements are known as Breeze and generally affect only local areas. Breeze causes immediate and very perceptible sensation of change. This can be avoided by appropriate screening and deflection of the breeze. The breeze does not raise the particulate matter, but also not allow the already air-borne-particulate matter to settle down.
  • Very low level, almost imperceptible air movements are called Draught. Draught occur in enclosed spaces due to the temperature and air pressure thresholds near cracks and other leakage points. Draughts do not cause any sensation of pressure on the skin, however, cause convective heat exchange, evaporation and dilution of pollutants in the air. Draughts cause localized cooling or heating of sensitive organs of our body. Such sensation on feet is a common experience in trains, buses, sofas, undersides of office tables, etc. Children and aged people with deficient blood circulation and body temperature regulatory mechanisms are readily affected by such currents.
Air can become mobile due to fans or such air circulating devices. Below 0.15 m/s air velocities, even if all other parameters of comfort are satisfactory, most people complain of stuffiness. Above 1.5 m/s air velocities, the air movement becomes annoying, such as papers being blown out or dust stirred up. However, under very hot and humid conditions people may tolerate such a situation for the sake of some thermal relief. A 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 opening is used to create turbulence or a viscous flow, and in hot humid climates body level stripe-opening generates a laminar flow to displace the humidity.  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.


In next Blog-post I will discuss “Temperature related comfort parameters” such as siting, size, shape and form (openings and other architectural features)  of the building, time-space scheduling of tasks, lifestyle setting, food and clothing.
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Sunday, December 1, 2013

Temperature mechanism of our Body and Interior Design




Understanding the human body temperature mechanism is very important for Interior Designers. It tells how the condition of human body and the space form determine the level of comfort and work productivity. In the longer term it also decides the well being of a person. Here in this article Body temperature mechanisms are described. In the follow-up articles (2) I intend to discuss spatial qualities and the ventilation systems that affect the body temperature mechanisms.


Climate affects our body system very profoundly. The climatic effects are primarily sensed by the skin. Five types of sensations are involved with the skin. The Touch-Pressure (mechanic-o receptors), Cold-Warmth feeling (thermo receptors), Pain and Itch. Cold is a consequence of contraction of blood vessels and warmth is felt due to dilation of blood vessels; both are felt by the same receptors.
Our body functions as a thermo equilibrium system. The thermal bearing capacity has upper and lower limits. The pain occurs at the upper limit of 52̊ C /126̊ F  and has a lower limit of 3̊ C / 37̊ F. The Optimum or the comfort level temperature depends on the level of acclimatization. In certain acute work conditions like mines, metal smelting plants, cotton spinning-weaving plants, cold storages, the level of efficiency or productivity depend on the endurance level and adaptability of the 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

Our body gains heat from the atmosphere and also dissipates excess heat to it, to maintain a thermo equilibrium. The human body maintains itself at an average temperature of 98.4̊ F / 37̊ C. There are many minor variations in body temperature, which are considered normal. Body temperature is lowest in the morning and highest in the evening, within a range of 1.5̊ F / 1̊ C. Infants have a very imperfect mechanism for regulation of body temperature. A fit of crying may elevate and a cold wash may lower the body temperature. Aged persons have a low metabolism and so maintain a lower body temperature. It takes much longer for an aged person to gain or dissipate body heat. Female body temperature is slightly lower than Male. The type food one takes affect the body temperature. High protein foods increase the body temperature. The act of ingestion and food digestion raise the body temperature. Exercise increases the body temperature, because only 25 % of muscular energy is converted into mechanical work, rest comes out as body heat. Atmospheric conditions like, temperature, humidity and movement of air, affect the efficiency of heat exchange from the body, and so the body temperature.

There are three types of heat generating processes in the human body. Conversion of food matter into useful energy is a continuous heat generating process. Muscular activities like even sedentary work or sleeping, are heat generating processes. Lastly, certain infections and dysfunctions within the body, elevate or lower the body temperature by extra ordinary rate of heat generation or weakened heat dissipation mechanism. Of all the energy produced in the body only 20 % is utilized, rest 80 % is surplus heat.

Normal skin temperature is between 31̊ and 34̊C. As the air temperature approaches the skin temperature heat loss from the body gradually decreases, vasomotor regulation will increase the body temperature to 34̊C to maintain the heat loss, but if air temperature is higher, the convective heat loss may not work.

As long as temperature of the opposite surface or object (sun, fire, radiator) is below skin temperature, the body can lose heat by radiation. But once it reaches an equilibrium occurs, body will rather gain heat by radiation. 

When the convective process is inoperative and radiation heat gain is positive, the body can maintain the thermal balance by evaporation. Evaporation can occur if air has velocity and appropriate humidity (low). Even in case of very high humidity conditions a high velocity air can remove the humidity.

A person exposed to constant high rate of sweating and permanent vaso-dilation can have lot of physical strain with loss of work efficiency.
The body must not only release all the excess heat that is generated from within the body, but all the excess heat as gained from the environment. Heat is lost from the body by radiation (60 %), evaporation (25 %), by convection and conduction (15 %).

Heat is lost through radiation, if there is a difference in temperature of opposing surfaces.  Evaporation heat loss is controlled by the level of humidity in the air (dryer the air, faster the evaporation), temperature of the air, body and rate of air movement. Body dissipates heat through evaporation by perspiration, sweat and exhalation of air. Convection occurs when the air in the vicinity of skin becomes hot, expands, decreases in density, and elevates to allow cooler air in its place. Rate of heat convection from body depends on the difference in temperatures (skin & surrounding air) and rate of air movement. Conduction depends on the difference between the body temperature and the contact object.

The body continues to accelerate or decelerate the heat loss till it reaches an equilibrium. Heat loss is accelerated by several body functions like perspiration, high transfer of heat to the skin by increased blood circulation (vaso-dilatation). When these prove to be insufficient, sweating occurs. In hot climates the heat loss rate is lower due to unfavourable atmospheric conditions. But by lowering of the body heat generation (lower metabolic and muscular activity), the net amount of heat to be dissipated can be reduced. But this requires some time to take effect. On immediate basis when the heat loss is not balanced with heat gain `heat stroke' occurs. In cold climates the heat loss is higher, so heat balance is achieved by conservation of heat and by appropriate heat gain. Heat production is raised by certain reflex secretions (adrenaline, thyroxine), higher intake of food (increased metabolic activity) by reflex shivering (muscular exercise) and by sufficient insulative protection. The body may control the heat loss by vaso-constriction (lower blood supply), and depressed sweating.

Many physical, chemical and bacterial agents disturb the heat regulation mechanism and cause fever. These may be due to increased heat production or reduced heat loss, or both.

In reptiles and amphibians heat regulation mechanism is absent. Their body temperature rises or falls with the atmospheric temperature. Hence they are called cold blooded animals. In abnormal temperature conditions they regulate the body temperature by suitable habitat. In winter they go deep into burrows or in hibernation (minimize the metabolic heat generation). Mammals and birds are known as hot blooded creatures, because the heat regulation mechanism is well developed, and they are able to maintain a level of body temperature.

Comfort of an occupant in an environment also depends on subjective variables or individual factors:
  1. Acclimatization: exposed to new conditions a person shortly (approx. 30 days) acclimatizes own-self.
  2. Age and sex: Older persons take much longer to adjust to temperature change, and as a result slightly higher temperature. Women also have slower metabolic rate than men so prefer a little higher temperature.
  3. States of health:


    Activity                                  heat output in watts

    Sleeping                                  70
    Sitting, typing                          130/160
    Standing, working at a bench  160/190
    Walking                                   220/290
    Digging                                   440/580
    Sustained hard work               580/700

BMR: Basal metabolism rate: It is the amount of heat given out by a person who is awake, but physically and mentally at rest in a comfortable condition of atmospheric temperature, pressure and humidity, 12/18 hours after a normal meal.

Normal BMR in an adult male is 40 Cal per sq. mt. of a body surface per hour. (females 37 Cal /sq. mt.). Average surface area of an adult male is 1.8 sq mts. In children BMR is high and as one ages it decreases. This is due to the fact that children have high surface area compared to their low weight. Generally higher the surface area greater is heat loss, but a large body also generates greater amount of heat.

In colder climates BMR is high to compensate the high rate of heat loss. In tropical climates BMR is purposely lowered by the body to retard the heat generation.

Muscular and energetic people have a high level BMR compared to people living a sedentary life.  Nature of diet affects the BMR. High protein foods have high BMR. After 2 hours of food ingestion BMR rises and maintains the high level for 4 hours.

Ductless glands (adrenal medulla, adrenal cortex, thyroxine, anterior pituitary and insulin) discharges increase the BMR. Any dysfunction of these glands affects the level of BMR.

Moderate pressure change (sea level to hilly regions) does not change the BMR. But a fall of pressure by ½ the normal barometer pressure (which occurs in very high mountaineering or in high altitude non pressure air craft flights) reduces the BMR. However increase in oxygen pressure (anesthesia) does not raise the BMR. 

For every 1 F rise in body temperature, as in case of fever, raises the BMR by 7 %. This is due to the fact that high body temperature increases the chemical processes of the body and so the BMR.

    Light exercise                           + 30 to 40 %
    Walking                                    + 50 to 60 %
    Severe Exercise                       + 100 %
    Mental work (maths problem)  + 3 to 4 %
    Strong emotions                        + 5 to 10 %
    Sleep                                         - 10 to 13 %

Conditions which increase the BMR
    Hyper thyroidism                   + 100 %
    Fever
    Diabetes insipidus
    Leukaemia                             + 20 to 80 %

Conditions which lower the BMR
    Starvation, malnutrition
    Hypo thyroidism
    Addison's disease
    Lipoid nephrosis.


. In the Follow-up articles (2) I intend to discuss spatial qualities and the ventilation systems that affect the body temperature mechanisms.


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