Report On ive Solar Design u675c

IVE SOLAR DESIGN. What is IVE Design? • is based upon climate considerations • attempts to control comfort (heating and cooling) without consuming fuels • uses the orientation of the building to control heat gain and heat loss • uses the shape of the building (plan, section) to control air flow • uses materials to control heat • maximizes use of free solar energy for heating and lighting • maximizes use of free ventilation for cooling • uses shade (natural or architectural) to control heat gain ive solar design refers to use of sun’s energy for heating and cooling of living spaces. In this approach, building itself or some element takes advantage of natural energy characteristics in materials and air created by exposure to sun. ive systems, have few moving parts, require minimal maintenance and require no mechanical systems. Operable windows, thermal mass and chimneys are elements of ive design. Operable windows- windows that can be opened. Thermal-mass- materials such as masonry and water that store heat energy for extended time. Prevents rapid temperature fluctuations. Thermal chimneys create or reinforce effect hot air rising to induce air movement for cooling purpose. ive design practiced throughout world and has been shown to produce buildings with low energy costs, reduce maintenance and superior comfort. Key aspects include solar orientation, use of thermal mass and appropriate ventilation and window placement. Most effective designs based on specific understanding of buildings sites wind patterns, terrain, vegetation, solar exposures and other factors. ive Solar Design: Introduction: Solar Energy is a radiant heat source causes natural processes upon which all life depends. Basic natural processes that are used in ive solar energy are thermal energy flows associated with radiation, conduction and natural convection. Sunlight striking on building, building materials reflect, transmit or absorb solar radiation, heat produced by sun causes air movement that can be predictable in designed spaces. ive solar energy means that mechanical means are not employed to utilise solar energy. Basic Design Strategies • • • • • • • • • • • •

Insulation Infiltration Control Shading Glazing Ventilation Lighting Lighting Controls Day Lighting Evaporative Cooling Thermal Mass Surface condition ive Solar Heating

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Don’t assume a strategy is right for every building • A nightclub will not benefit from daylighting • Buildings located along the expressway may not want natural ventilation • Evaporative cooling is not effective in the south • Shading is not important in areas dominated by overcast skies Strategies should be project specific ive solar systems rules of thumb: Building should be elongated on an east-west axis. Buildings south face should receive sunlight between hours of 9.00 a.m. and 3.00p.m. (suntime) during heating season, Interior spaces requiring most light and heating and cooling should be along the south face of building. Less used spaces should be located on the north. An open floor plan optimizes ive system operation. Use shading to prevent summer sun entering the interior.

IVE SOLAR HEATING:

Two primary elements of ive solar heating are required: • south facing glass • thermal mass to absorb, store and distribute heat. Three approaches to ives systems –Direct gain, indirect gain and isolated gain. Goal of all ive solar heating systems is to capture sun’s heat within building’s elements and release heat during periods when sun is not shining.

DIRECT GAIN In this system, actual living space is a solar collector, heat absorber and distribution system. South facing glass its solar energy into house- strikes directly and indirectly thermal mass materials- such as masonry floors and walls. Direct gain systems utilize 60-75% of sun’s energy striking windows. Thermal mass floors and walls are functional parts. Also possible to use water containers inside to store heat. There must be an expanse of south-facing glass and enough thermal mass, strategically located in a space for heat absorption and storage.

The direct gain system makes overt use of solar geometry to ensure that sun reaches the thermal mass in the winter, and that shading devices prevent solar access during the months where cooling is the dominant issue. INDIRECT GAIN In indirect gain system, thermal mass is located between sun and living space. Thermal mass absorb sunlight and transfer it to living.space by conduction. Indirect gain system utilize 30-45% of sun’s energy striking the glass ading thermal mass. There are two types of indirect gain systems: 1. Thermal storage wall systems (Trombe walls) 2. Roof pond systems. Thermal storage wall systems (Trombe Walls) Thermal mass is located behind south glass in system. Operable vents at top and bottom of thermal storage wall permit heat to convect from between the wall and glass into living space.

Trombe Wall with Vents

Whether or not a wall has flaps, and flaps that automatically close off when the air direction reverses, becomes a critical issue in making sure that preheating of the room occurs in the morning hours.

Roof pond systems Six to twelve inches of water contained on a flat roof. This system best for cooling in low humidity climates but modified to work in high humidity climates, Water stored in large plastic or fibre glass containers covered by glazing and space below is warmed by radiant heat from warm water above, require elaborate drainage systems, movable insulation to cover and uncover water at appropriate times and structural sys tem to dead load.

ISOLATED GAIN Isolated gain system has integral parts separate from main living area of a house, Examples: sunroom and a convective loop through an air collector to a storage system in house. Utilizes 15-30% of sunlight striking glazing toward heating ading living areas. Sunrooms employ combination of direct and indirect gain system features. Sunlight entering sunroom retained in thermal mass and air of the room. Sunlight brought into house by conduction through shared mass wall in rear of sunroom or vents that permit air between sunroom and living space. Use of south facing air collector to naturally convect air into storage area. These are ive collectors. Collective air collectors located lower than storage areas so heated air generated in collector rises into storage area and replaced by air from lower cooler section. Heat c an be released from storage area either by opening vents –access storage by mechanical means, or by conduction if storage is built into house. Sunroom – provide additional usable space to house and plants can be grown effectively. Convective air collector are more complex. Drawback in this area, where space heating is less of a concern than in colder regions where system used longer. SUNSPACE

What is a Convective Air Loop?? Convective Air Loop -- a ive solar heating system that consists of a solar collector and a thermal storage mass (usually a rockbed) isolated from the living spaces. Air is used to transfer heat from the collector to the storage and the living spaces.

Hybrid System -- A predominantly ive solar heating system which utilizes an active component, such as a fan, to force heat from one location to another. Rockbed -- a heat storage component consisting of an enclosed volute of rocks (fist-sized) with a plenum at each end. During the charging cycle, warm air from the solar collector is circulated through the rocks, warming them. During the discharge cycle, cool room air is circulated through the rocks where it is heated and returned to the room.

IVE SOLAR COOLING

ive cooling is the counterpart of ive heating. While ive heating is driven only by the sun, ive cooling can use various heat sinks and climate influences to decrease heat. 1. Ventilative Cooling 2. Dehumidification 3. Evaporative Cooling 4. Radiative Cooling 5. Mass effect Cooling

These design strategies reduce heat gains to internal spaces. • • • • • • • •

Natural Ventilation Shading Wind Towers Courtyard Effect Earth Air Tunnels -Evaporative Cooling ive Down Draught Cooling Roof Sprays

Ventilative Cooling VENTILATION AND AIR MOVEMENT Functions of ventilation: Natural ventilation and air movement could be considered under heading of ‘structural controls’ as it does not rely on any form of energy supply or mechanical installation. It has 3 different functions • Supply of fresh air • Convective cooling • Physiological cooling Radial difference in form of provisions of 1,2 and 3. First 2 functions as ‘ventilation’ but last one as ‘air movement’. SUPPLY OF FRESH AIR: Requirement of fresh air supply governed by type of occupancy, number and activity of occupants and by nature of any processes carried out in space. Requirement may be stipulated by building regulations and advisory codes or in number of air changes per hour, but applicable only to mechanical installations. Can be taken as useful guides for natural ventilation faced and solutions less and not workable. Provision of permanent ventilators i.e. of openings which cannot be closed, compulsory with grills or ‘air-bricks’ built in wall or incorporated with windows. Size of openable windows on floor area/ volume of room. Aim of these rules to ensure ventilation but rigid application often inadequate to ensure satisfactory performace principle involved must be understood. You have to not only provide openings but also, locate them correctly, make sure they are large enough, for this to work properly!! CONVECTIVE COOLING Exchange of indoor air with fresh air out-door provide cooling, if latter at lower temperature than indoor air. Moving air acts as heat carrying medium. Useful in moderate or cold climates. PROVISION FOR VENTS; STACK EFFECT. Ventilation, i.e., both supply of fresh air and convective cooling, involves slow movement of air and can be either thermal or dynamic wind. Stack Effect relies on thermal forces, set up by difference between indoor and outdoor air. When air is still it can occur through an open

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window, warmer and lighter indoor air will flow out at top and cooler, denser out-door air will flow in at bottom. Special provision made for it in form of ventilating shafts. Higher the shaft, more is cross-sectional area with greater temperature difference, more motive force, therefore more air will be moved. Motive force is ‘stack pressure’ x cross sectional area (force-Newtons, area- m²), Ps = Stack pressure Therefore Ps = 0.042 x h x •T Where Ps= stack pressure in N/m² h = height of stack in m. •T = difference in temperature in °C. 0.042 = constant in N/m²,°C. Such shafts used for baths, toilets, etc. most satisfactory under winter conditions when temperature difference enough to generate air flow. PHYSIOLOGICAL COOLING: Movement of air past skin surface accelerate heat dissipation in 2 ways: Increasing convective heat loss Accelerating evaporation. For this to take place, higher temperature tolerated with air velocity are required. In low humidities (below 30%) this cooling not great, as restricted evaporation even with very less air movement. In high pressure (> 85%) cooling effect is restricted as higher pressure prevents evaporation, but greater velocities (> 1.5 to 2m/s) have some effect. Most significiant in medium humidities (35-60%) cooling by air movement is most needed where there are no other forms of heat dissipation available, when air as warm as skin, surrounding surface also at similar temperature. PROVISION FOR AIR MOVEMENT: WIND EFFECTS Thermal forces rarely sufficient to create appreciate air movements. Only ‘natural’ force can be relied on is dynamic effect wind. When creation of air movements indoor is the aim, designer should capture as much of wind available as possible. Negative control- when wind is too much, easy is window and openings can be shut. Local conditions can change wind patterns on micro-climatic scale. In same way as wind is generated by pressure difference so an air flow through building is result of a pressure difference between 2 sides. Air although light has a mass (1.2kg/m³) and as it moves, has momentum- product of mass and its velocity (kgm/s). this is vector quantity, which can be changed in direction or in magnitude only by other force. Moving air on striking an obstacle (building), will slow down air flow but will exert pressure on obstructing surface. This pressure is proportionate to air velocity, as expressed by: Pw = 0.612 V² Where Pw = wind pressure in N/m²

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V = wind velocity in m/s 0.612 = constant = Ns²/m• This slowing down process effects a roughly wedge-shaped mass of air on windward side of building, which in turn diverts rest of air flow upward and sideways. A separation layer is formed between stagnant air and building on one hand and laminar air flow on other. Laminae air flow itself may be accelerated at obstacle, as area available for flow is narrowed by obstacle. At separation layer, due to friction, upper surface of stagnant air is moved forward, turbulence or vortex is developed. A stagnant mass of air is formed on leeward side, but is at reduced pressure. It is not stagnant: a vortex is formed, movement is light and variabl e and after referred as ‘wind shadow’. If building has an opening facing high pressure sone and another low pressure zone air movement will be generated through building.

AIR FLOW THROUGH BUILDINGS: As no satisfactory and complete theory is available, air flow patterns can be predicted on basis of empirical values derived from measurements in actual buildings/ in wind tunnel studies. Such empirical rules five useful guide to designwe in critical cases.

Following factors can be isolated which effect indoor air flow: a. b. c. d. e. f.

Orientation External features Cross-ventilation Position of openings Size of openings Controls of openings.

a) ORIENTATION: greatest pressure on windward side of building is generated when elevation at right angles to wind direction, so greatest indoor air velocity received in this case. Wind flow incident at 45° reduce pressure by 50% thus, designer must ascertain prevailing wind direction from wind frequency charts of wind roses and must orient his building to get largest openings facing wind direction. Wind shadow is less if building is perpendicular to wind flow and is greatest when building is more than 45° to wind flow.

It may happen that optimum solar radiation and optimum orientation for wind do not coincide. In equatorial regions a N-S orientation would be preferred for sun but wind is east oriented. These may resolve contradictory requirements.

a

b

b

a
WING WALLS

c) CROSS VENTILATION: In absence of an outlet opening or with a full partition there can be no effective air movement through a building when in case of strong winds. With a windward opening and no outlet, a pressure similar to that of front of building will e built indoors, make conditions even worse, increase discomfort. In some cases, oscillating pressures changes, ‘buffering’, can occur, produced by opening on leeward sid e with no inlet.

d) POSITION OF OPENING: Air movement must be directed at body surface. Means, that air movement ensured through space mostly used by occupants: through ‘living zone’, (upto 2m high). Difference in position of inlet openings create a more difference in flow of air through room. e) SIZE OF OPENINGS: best arrangement in full openings on both sides, with adjustable sashes or closing devices which assist in channelling air flow in required direction, following change of wind. f) CONTROLS OF OPENINGS: Sashes, canopies, louvers and other elements controlling openings, also influence indoor air flow pattern. Mosquito nets, fly screens, etc. reduce velocity of air. The percent of reduction in velocity may depend on material of there screens. AIR MOVEMENT AND RAIN: Exclusion of rain not a different task and making provision for air movement does not create any particular difficulties, between 2 together and simultaneously is no means easy. Opening of windows during periods off wind driven rain it rain and spray; while closing windows create intolerance conditions indoors. Conventional tilted louvre blades are unsatisfactory:

1) 2)

Strong wind will drive rain in, even upwards through louvers. Air movement will be directed upwards from living zone.

Verandah and large roof overhands are perhaps best traditional methods of protection. AIR FLOW AROUND BUILDINGS: Effect of tall blocks mixed development has been examined in experiments conducted by Building Research Station at Garston. Air stream separates on face of a tall block, part of it moving up and over roof part of it down, form a large vortex, leading to very high pressure build-up. An increased velocity found at ground level at sides of tall block could serve as useful purpose in climates, if tall block not fully closed but permeable to wind-effect would be reduced. a) If in rural setting in open country, single storey buildings placed rows in a grid-iron pattern, stagnant air zones leeward from first row overlap with second. Spacing of six times of building height is necessary to ensure adequate air movement for second row. Five times height rule for spacing not satisfactory. b) In similar setting, buildings are staggered in a checker-board pattern, flow field is much more uniform, stagnant air zones almost eliminated. VENTILATION AND OPERABLE WINDOWS. Primary strategy for cooling buildings without mechanical assistance (ive cooling) in hot humid climates to employ natural ventilation. In Austin area, prevailing summer breezes are from south and southeast. This matches with increased glazing on south side needed for ive heating, making it possible to achieve helpful solar gain and ventilation with following strategies. • • •

Place operable window on south exposure Casement windows offer best air will be directed to ceiling. Awing windows offer best rain protection and perform better than double hung windows, If a room can have windows on only one side, use two widely spaced windows instead of one.

Wing Walls: Wing walls-vertical solid s placed along side of window perpendicular to wall on windward side of house. Wind walls accelerate natural wind speed due to pressure difference created by wind wall. Thermal chimney (Stack ventilation): A thermal chimney employs convective currents to draw air out of a building. By creating warm or hot zone within exterior exhaust outlet, air can be drawn into house ventilating structure. Sunrooms designed to perform this function. Excessive heat generated in south facing sunrooms during summer can be vented at top. With connecting lower vents to living space open along with windows on north side, air is drawn through living space to be exhausted through sunroom upper vent. Thermal chimney constructed in a narrow configuration with heated black metal absorber on inside behind a glazed front that can reach high temperature and be insulated from house. Chimney must terminate above roof level. A rotating metal scoop at top opens opposite the wind will allow heated air to exhaust without being overcome by prevailing wind. Thermal chimneys effects can be integrated into house with open stairwells and atria.

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Other Ventilation strategies: Make outlet openings slightly larger than the inlet openings Place the inlets at low to medium heights to provide airflow at occupant levels in room inlet close to wall result in air “washing” along the wall. Centrally located inlets for air movement in centre areas of room. Window insect screen decrease velocity of slow breezes more than stronger breezes. Screening a porch will not reduce air speeds. Night ventilation done at rate of 30 air changes per hour or greater. Mechanical ventilation required to achieve this. High mass houses cooled with night ventilation providing fabric furnishings minimum. Keep high mass house closed during day and opened at night.

Stack Effect (i.e. warm air rises):

COURTYARD EFFECT Due to incident solar radiation in a courtyard, the air gets warmer and rises. Cool air from the ground level flows through the louvered openings of rooms surrounding a courtyard, thus producing air flow. At night, the warm roof surfaces get cooled by convection and radiation. • If this heat exchange reduces roof surface temperature to wet bulb temperature of air, condensation of atmospheric moisture occurs on the roof and the gain due to condensation limits further cooling. • •

If the roof surfaces are sloped towards the internal courtyard, the cooled air sinks into the court and enters the living space through low-level openings, gets warmed up, and leaves the room through higher-level openings. However, care should be taken that the courtyard does not receive intense solar radiation, which would lead to conduction and radiation heat gains into the building. DEHUMIDIFICATION: HUMIDITY CONTROL Dehumidification only possible by mechanical means without this, in warm-humid climates, some relief is provided by air movement. In hot-dry climates humidification of air may be necessary, associated with evaporative cooling. In these climates, buildings normally closed to preserve cooler air retained within structure of high thermal capacity, exclude sand and dust carries by winds. Some form of air supply to building interior is necessary. All these functions: • • • •

Controlled air supply Filtering out sand supply: Evaporative cooling. Humidification.

are served by a device wind scoop. Large intake openings capture air movement above roofs in densely built up areas. Water seeping through porous pottery jars evaporates, some drips down onto charcoal placed on a grating, through which air is filtered. Cooled air assists downward movement, reversed stack effect. In India, curtain made of cascas grass is hung in front of windows on windward side, this is wetted by throwing a bucket of water against it. Grass is highly absorptive and retains moisture for long time. Wind ing through loose textured mat curtain is cooled and humidified. The ‘desert cooler’ developed is a cube shaped frame, of 500 to 600 mm sides. Top and bottom are shallow tanks. Sides are covered with cascas mats. Top of which immersed in upper tank. Water seeps down through mat and collected in lower tank. Inside box is an ordinary table fan, which blows air through cascas mat, cooling and humidifying it. What is Evaporative Cooling?: The exchange of sensible heat in the air for the latent heat of water droplets of wetted surfaces. It may be used to: • cool the building (where wetted surfaces are cooled by evaporation), • building air (cooled directly by evaporation or indirectly by with a surface previously cooled by evaporation), • or the occupants (where evaporation of perspiration cools the skin surface.) Sensible heat is the dry heat in the air. Latent heat is the wet heat released into the air as water changes from liquid to vapour by evaporation or boiling. • Evaporative cooling lowers indoor air temperature by evaporating water. • It is effective in hot and dry climate where the atmospheric humidity is low. • In evaporative cooling, the sensible heat of air is used to evaporate water, thereby cooling the air, which, in turn, cools the living space of the building. • Increase in between water and air increases the rate of evaporation.

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•

The presence of a water body such as a pond, lake, and sea near the building or a fountain in a courtyard can provide a cooling effect.

1. 2. 3. 4. 5.

Ground cover Water sprinkler Insulated roof Shading trees Water trough

IVE DOWN DRAUGHT COOLING • Evaporative cooling has been used for many centuries in parts of the middle east, notably Iran and turkey. • In this system, wind catchers guide outside air over water -filled pots, inducing evaporation and causing a significant drop in temperature before the air enters the interior. • Such wind catchers become primary elements of the architectural form also. • ive downdraught evaporative cooling is particularly effective in hot and dry climates. It has been used to effectively cool the Torrent Research Centre in Ahmedabad.

WIND TOWER

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In a wind tower, the hot air enters the tower through the openings in the tower, gets cooled, and thus becomes heavier and sinks down. The inlet and outlet of rooms induce cool air movement. In the presence of wind, air is cooled more effectively and flows faster down the tower and into the living area. After a whole day of air exchanges, the tower becomes warm in the evenings. During the night, cooler ambient air comes in with the bottom of the tower through the rooms. The tower walls absorb heat during daytime and release it at night, warming the cool night air in the tower. Warm air moves up, creating an upward draft, and draws cool night air through the doors and windows into the building. The system works effectively in hot and dry climates where fluctuations are high. A wind tower works well for individual units not for multi -storeyed apartments. In dense urban areas, the wind tower has to be long enough to be able to catch enough air. Also protection from driving rain is difficult.

EARTH AIR TUNNELS • Daily and annual temperature fluctuations decrease with the increase in depth below the ground surface.

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At a depth of about 4 m below ground, the temperature inside the earth remains nearly constant round the year and is nearly equal to the annual average temperature of the place. A tunnel in the form of a pipe or otherwise embedded at a depth of about 4 m below the ground will acquire the same temperature as the surrounding earth at i ts surface.

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Therefore, the ambient air ventilated through this tunnel will get cooled in summer and warmed in winter and this air can be used for cooling in summer and heating in winter.

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This technique has been used in the composite climate of Gurgaon in RETREAT building. The living quarters (the south block of RETREAT) are maintained at comfortable temperatures (approx. 20-30 degree Celsius) round the year by the earth air tunnel system, supplemented, whenever required, with a system of absorption chillers powered by liquefied natural gas during monsoons and with an air washer during dry summer. However, the cooler air underground needs to be circulated in the living space. Each room in the south block has a 'solar chimney; warm air rises and escapes through the chimney, which creates an air current for the cooler air from the underground tunnels to replace the warm air. Two blowers installed in the tunnels speed up the process. The same mechanism supplies warm air from the tunnel during winter.

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IVE SPACE CONDITIONING USING EARTH AIR TUNNEL SYSTEM

What is Radiative Cooling?: Transfer of heat from warmer surface to cooler surrounding surface (or outer space). It may be used to cool the building (where warm building surfaces radiate heat to the sky) or to cool the people (where the warm skin radiates heat to the cooler building surfaces -- to the cool walls of an underground building, for example. Earth Berming used to cool buildings

Green roof on the Vancouver Public Library

ROOF SPRAYS What is Mass Effect Cooling?: The use of thermal storage to absorb heat during the warmest part of the day and release it during a cooler part. “Night flushing”, where cooler air is drawn through a building to exhaust heat stored during the day in massive floors and walls is an example of daily -cycle-masseffect-cooling. A good strategy to couple with direct gain ive solar systems that will t end to absorb heat from its thermal mass component during the day of hot cycles.

IVE SOLAR STRATEGIES : LIGHTING Lighting or illumination deliberate application of light to achieve practical or aesthetic effect. Lighting includes artificial light sources such as lamps and light fixtures as well as natural illumination by capturing daylight. Daylighting (windows, skylights or light shelves)used as main source of light during daytime in buildings. This can save energy compared with artificial lighting, represents major component of energy consumption in buildings. Proper lighting can enhance task performance,improve appearance of an area and have positive physiological effects on occupants. Lighting Strategy • General lighting Use low levels of illumination for the general area Use efficient fixture Use affective control system • Task lighting Use higher levels of illumination at work stations The combined strategies results in a much lower watts / sq.ft. figure.

Daylighting Daylighting practise of placing windows or other openings and reflective surfaces so that during the day natural light provides effective internal lighting. Artificial lighting energy use can be reduced by installing fewer electric lights because daylight is present or switching electric lights automatically in response to presence of daylight- process known as Daylight Harvesting. Amount of daylight received in an internal space can be analysed by undertaking a daylight factor calculation. Use of computers and proprietary industry software such as Radiance allow architects or engineer to quickly undertake complex calculations to review benefit of a particular design. Daylighting The Challenges: 1. Using sunlight without over heating 2. Getting light to the interior of the space

Window Windows most common way to it daylight into space. Vertical orientation that they selectively it sunlight and diffuse daylight at different times of day and year. Windows on multiple orientations combined to produce right mix of light for building, depending on climate and latitude. These are three ways to improve amount of light available from a window. •

Place window close to a light coloured wall

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• •

Slant sides of window openings so inner opening is larger than outer opening Use a large light coloured window sill to project light into room

Different types and grades of glass and different window treatments can also effect amount of light transmission through the windows. Glazing • Glazing properties • U value – pertains only to conduction – has not affect on direct radiation • SHGC – percentage of solar energy allowed through the glass • Glazing options • Clear single pane high SHGC .90 • Clear insulated glass high SHGC .85 • Heat absorbing (tinted) moderate SHGC .60 • Reflective glass low SHGC .35

Clear

Heat absorbing

Reflective

South facing glass must: • limit the quantity of light to avoid over heating. • Avoid direct beam radiation reaching the building interior. Diffuse the light.

CLERESTORY WINDOWS Another important element is creating daylighting is use of clerestory windows. These are high, vertically-placed windows, used to increased direct solar gain when oriented towards equator. Case of a ive solar house, clerestories may provide a directly light path to polar-side rooms that would otherwise be not illuminated. Clerestories can be used to it diffuse daylight that illuminates a space such as a classroom or office, walls placed so as to reflect indirect light to interior areas where it is needed. Method has advantage of reducing directionality of light to make it softer and more diffuse, reducing shadows.

SKYLIGHTS Skylight is any horizontal window, placed at roof of building, often used for daylighting white translucent acrylic is a ‘Lambertian Diff’ transmitted light transmitted light is perfectly diffused and distributed evenly over affected areas. Skylights it more light per unit area than windows and distribute more evenly over a space. Optimal area of skylights varies according to climate, latitude and characteristics of skylight, but is 4-8% of floor area. Thermal performance of skylight is affected by stratification i.e. tendency of warm air to collect skylight wells, which in cold climates increases rate of heat loss. Poorly constructed or installed skylights may have leaking problems and single paned skylights may weep with condensation. Using modern designs with proper installation will eliminate issues with leaks and provide greater energy efficiency. – –

Lower winter angles = less light Higher summer angles = more heat

LIGHT SHELVES Light shelves are an effective way to enhance lighting from window, this effect being obtained by placing a white or reflective metal light shelf outside the window. Usually window protected from direct summer season sun by a projecting eave. The light shelf projects beyond shadow created by eave and reflects sunlight upward to illuminate the ceiling. This reflected light can contain little heat content and reflective illumination from ceiling will typically reduce deep shadows, reducing need for general illumination. Light shelves made of an extruded aluminium chasis system and aluminium composite surfaces. Extruded components can be painted or anodized and they are all field fabricated and assembled from stock lengths.

Light shelves used in high-rise and low rise office buildings, as well as institutional buildings. LIGHT TUBES Light tubes also called solar tube which is placed into a roof and its light to a focussed area of interior. Resemble recessed ceiling light fixtures. Do not allow as much heat transfer as skylights because they have less surface area.

TUBULAR DAYLIGHTING DEVICES (TDDs) Use modern technology to transmit visible light through opaque walls and roofs. Tube is ive component consisting of reflective interior coating or a light conducting fibre optic bundle. It is frequently capped with a transparent, roof -mounted dome ‘light collector’ and terminated with a diff assembly that its daylights into interior spaces and distributes available light energy evenly. It is more energy efficient than skylight since less energy escapes from interior due to less surface area.

ATRIA / LIGHT WELLS

SAWTOOTH ROOF Another roof-angled glass is a ‘saw tooth roof’ sawtooth roof have vertical roof glass facing away from equator side of building to capture diffused light. Angled portion of glass- structure is opaque and well insulated with cool roof and radiant barrier. Sawtooth roof’s lighting concept partially reduces summer “solar furnace” skylight problem, with significant undesirable heat transfer.

HELIOSTATS Use of heliostats, mirrors which are moved automatically to reflect sunlight in a constant direction as sun moves across sky, is gaining popularity as an energy-efficient method of lighting. Heliostat used to shine sunlight directly through a window or into any arrangement of optical elements, that distribute light where it is needed.

SMART GLASS Glass of materials that can be switched between a transparent, reflective or retro-reflective. Switching is done by applying an electric voltage to material or by performing some mechanical operations. 4 types of glazing are studies for their dynamic performance (glare, solar control and visibility)

ELECTROCHROMIC GLASS Is glazing that changes its opacity depending on amount of sunlight being received. This is tested for its light and heat control. PHOTOVOLTAIC GLASS Has dual function of providing shading and generating power at same time. This is being tested for its efficiency, impact on view, shading, heat absorption and re -radiation. DOUBLE GLAZED UNIT (DGU) With internal operable glass is studied for its impact on view, shading and heat absorption. These consist of blinds between glass which can be turned up during strong sunlight. Doubling of glazing used in all air-conditioned areas. Single glazing used in classrooms and school halls. FIBRE OPTIC CONCRETE WALLS Another way to make secure structural concrete well translucent is to embed optical fibre c ables in it. Daylight can then directly through solid-concrete wall. LiTraCon trademark for translucent concrete building material. Light Transmitting Concrete ( Li Trs Con).

Technical data sheet from manufacturer says the material is made of 96% concrete and 4% by weight of optical fibres. Developed in 2001 by Architect A’ron Lononczi.

SOLARIUM In well designed isolated solar gain building with solarium, sunroom, greenhouse, etc. there is glass on southern side. A large area of glass can be added between sunroom and interior living quarters. Low-cost high-volume product ratio door safely glass inexpensive way to accomplish this goal. Doors used to enter a room, should be opposite sunroom interior glass. Halls minimised with open spaces used instead. Drapes over interior glass used to control lighting. They can be automated with sensor-based electric motor control-aware of occupancy, daylight, interior temperature and time of day. To help distribute sunroom daylight to the sides of rooms that are farthest from the sun side, inexpensive ceiling-to-floor mirrors can be used.

DAYLIGHTING CONCEPTS It is important for daylighting design process to involve integration of many disciplines including mechanical, electrical and lighting. Design team needed to be brought into process early to ensure daylighting concepts and ideas carried throughout the project.

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