Passive Solar HousingPassive solar systems are self-sufficient buildings which rely on naturalprinciples insted of mechanical systems to provide a non-pollutingsource of heating and cooling.IntroductionPassive energy is more sustainable than active energy systems because passivesystems use far fewer natural resources to build and maintain. They do not rely soheavily upon gas for heating or coolants for air conditioning. Passive systems aredesigned so that they can take natural energy from the sun to heat a building anduse specific design principles to cool a building. Passive energy systems are also cheaper thanactive systems because they are less susceptible to malfunction since they rely completelyupon nature, rather than using mechanical equipment to produce energy. In orderto create a home that will maximize the effects of passive solar heating, a designermust take many different variables into account. Two major ideas crucial to creatingeffective passive solar housing are orientation and materials. Passive solar buildingsshould be oriented to receive as much southern sun as possible. In the summer,the hot sun can be blocked by using overhangs or through landscaping like largefoliated trees. In the winter, sun should help heat the house because the sun angleis lower in the sky allowing more sun to hit the glazing more directly. Thoughtshould also be given to the specifications of the windows for maximum solar gainsand heat loss. By using the right building materials such as masonry or concrete andcombining them with effective insulation, solar energy can be contained in thehouse allowing it to be comfortable year round(Desbarats 1980, 232).Building OrientationBuilding orientation is crucial to maximizing energy production in a passive solarhome. Because passive solar homes rely on natural sunlight to power the building'sutilities, the building should be oriented on the site in a way that will allow it tomaximize the amount of sunlight. The best way to achieve this is to orient the houseon the east-west axis and concentrate most of the house's glazing on the southwall. This allows the home to receive the most direct sunlight for the longest periodof time(Hibshman 1983, 261). Heat travels through windows very easily, however heatdoes not exit as easily. Once the heat passes through the window, it breaks up and ittakes much longer for that heat to exit(Button 1993, 129). This allows heat that enters abuilding to stay in the building for a long time. This is a helpful principal for heatinga building in the winter and is the reason why windows should receive as much lightas possible in the winter. However, in the summer, the hot sun can become anuncomfortable problem. To alleviate some of this heat, passive solar homes shouldbe designed with attic fans or some sort of operable clerestory windows which canbe opened to release some of the hot air when it rises. Glazing should be greatlyreduced on the east and west walls and should be virtually eliminated on the northside of the home because most cold winds in winter come from the north andwest(Desbarats 1980, 56). Because the house needs as much protection from thesewinds as possible, and glazing cannot provide this protection, windows should beeliminated.(Desbarats 1980, 28).Glass The amount as well as type of glass windows used in a house are very importantconsiderations in terms of thermal comfort, cost and efficiency. There are manydifferent types of windows available: single, double and triple paned(Button 1993, 164)A single pane is simply one pane of glass. These are generally the worst types of windowsto use. Although they are the cheapest windows available, they are not energy efficientand they allow more heat gain in summer and heat loss in winter than either the doubleor triple paned windows do. Double pane windows are much more energy efficient.The reason is the cold winter air passes through the first pane but then must passthrough a gap of either air or Argon gas before it reaches the second pane. The reasonthis is helpful is because air or Argon gas provide excellent insulation and do not allowthe cold to penetrate nearly as much as it would if there were only one pane. Triplepaned windows work on the same principal as double paned but they are even moreenergy efficient because there is even an additional layer of insulation(Button 1993, 166). It isalso possible to get windows with coatings such as low emissivity coatings (low-E)which help to block the suns harmful rays but still allow visible light to pass through(Button 1993, 173).(Hibshman 1983, 29) R-Values for Different Types of GlassThermal Mass Thermal mass is another important concept to keep in mind when dealing with energyefficient housing. It is important for these types of homes to be built with materialsthat have a large amount of thermal mass(Hibshman, 1983, p.48). Such materials are brick,stone and concrete. These materials are ideal because materials with a large thermal massabsorb much of the energy they receive from the sun. These materials absorb and release energycompletely, but slowly. Because it takes a long time for the energy to be releasedafter it is absorbed, a phenomenon known as lag, warm sunlight that is absorbedduring the day is finally released over time at night. This is another natural phenomenonwhich proves helpful because it provides warmth at night when the house is the coldest andheat is necessary. Because all of the heat is released at night the floor is then cool for thenext day and consequently this helps to cool the rest of the house. It is also important leavethe concrete floors on the south side of the house exposed. If they are carpeted, they lose mostall of their thermal mass properties. However, carpeting would be acceptable on thenorth side of the house because there should be almost no windows there anyway(Hibshman, 1983, p.32).(Hibshman, 1983, p.32) How Thermal Mass WorksAffordability in Sustainability Using Passive Solar HeatingCost is a very important factor for designing sustainable architecture. Aside from creatingenviornmentally friendly architecture, sustainable architecture allows lower building andmaintenance costs. Affordability goes hand in hand with sustainablity and is something whichwe, as designers, should concentrate on when designing the housing in East St. Louis. One wayto create affordable homes is by using everyday, affordable materials to replace expensive andwasteful mechanical ones. One way this can be achieved is by using 55-gallon drums filled withwater to create thermal mass, a very necessary element for passive solar heating. By placing thesedrums in direct sunlight, they will absorb the sun's energy and, because lag also occurs in water,they will have the same effect on the house that materials like concrete or masonry would, butwithout the cost(Hibshman, 1983, p.50). Another, affordable solution is to use these drumsfilled with water to replace water heaters. They can be placed in the roof or any other placewhere they will receive a lot of direct sunlight (see figure on "Sustainable Design" page).The owner can then use that water which has been naturally heated for bathing or cooking,replacing a mechanical hot water heater and greatly reducing cost(Hibshman, 1983, p.53).Another way to create affordable yet sustainable architecture is by using unconventionalbuilding techniques. One way is to use post-and-beam units instead of conventional stickframing. The posts are then anchored into the concrete. This creates a very stable framingsystem and also reduces costs because no 2"x4" studs are used and therefore, less wood isused. However, the most important money saving factor in this construction is the use ofprefabricated wall systems. These systems are cut into 4'x8' sheets and can thenbe placed right in between the posts on the construction site with no wated materials used(Hibshman, 1983, p.71). This is also a faster method of construction so the labor costswill also be reduced. While these are just a few ideas more specific examples using thesetechniques can be found in the sited material.Diagram showing good passive solar design(Hibshman, 1983, p.71)Previous -Next

Passive solar building designFrom Wikipedia, the free encyclopedia

Elements of passive solar design, shown in a direct gain application

Activeand passive solar systems are used in theSolar Umbrella houseto achieve nearly 100%energy neutrality.Inpassive solar building design, windows, walls, and floors are made to collect, store, and distributesolar energyin the form of heat in the winter and reject solar heat in the summer. This is called passive solar design or climatic design because, unlike activesolar heatingsystems, it doesn't involve the use of mechanical and electrical devices.[1]The key to designing a passive solar building is to best take advantage of the localclimate. Elements to be considered include window placement and glazing type,thermal insulation,thermal mass, and shading. Passive solar design techniques can be applied most easily to new buildings, but existing buildings can be adapted or "retrofitted".Contents[hide] 1Passive energy gain 2As a science 3The solar path in passive design 4Passive solar thermodynamic principles 4.1Convective heat transfer 4.2Radiative heat transfer 5Site specific considerations during design 6Design elements for residential buildings in temperate climates 7Efficiency and economics of passive solar heating 8Key passive solar building design concepts 8.1Direct solar gain 8.2Indirect solar gain 8.3Isolated solar gain 8.4Heat storage 8.5Insulation 8.6Special glazing systems and window coverings 8.7Glazing selection 8.7.1Equator-facing glass 8.7.2Roof-angle glass / Skylights 8.7.3Angle of incident radiation 8.8Operable shading and insulation devices 8.9Exterior colors reflecting - absorbing 9Landscaping and gardens 10Other passive solar principles 10.1Passive solar lighting 10.1.1Interior reflecting 10.2Passive solar water heating 11Comparison to the Passive House standard in Europe 12Design tools 13Levels of application 13.1Pragmatic 13.2Annualised 13.3Minimum machinery 13.4Zero Energy Building 14See also 15References 16External linksPassive energy gain[edit]Passive solartechnologies usesunlightwithout active mechanical systems (as contrasted toactive solar). Such technologies convert sunlight into usable heat (water, air, thermal mass), cause air-movement forventilating, or future use, with little use of other energy sources. A common example is asolariumon theequator-side of a building.Passive coolingis the use of the same design principles to reduce summer cooling requirements.Some passive systems use a small amount of conventional energy to control dampers, shutters, night insulation, and other devices that enhance solar energy collection, storage, and use, and reduce undesirableheat transfer.Passive solar technologies include direct and indirectsolar gainfor space heating,solar water heatingsystems based on thethermosiphonorgeyser pump, use ofthermal massandphase-change materialsfor slowing indoor air temperature swings,solar cookers, thesolar chimneyfor enhancing natural ventilation, andearth sheltering.More widely, passive solar technologies include thesolar furnaceandsolar forge, but these typically require some external energy for aligning their concentrating mirrors or receivers, and historically have not proven to be practical or cost effective for widespread use. 'Low-grade' energy needs, such as space and water heating, have proven, over time, to be better applications for passive use of solar energy.As a science[edit]Thescientificbasis forPassive Solar Building Design[2]has been developed from a combination ofclimatology,thermodynamics( particularlyheat transfer:conduction (heat),convection, andelectromagnetic radiation),fluid mechanics/natural convection(passive movement of air and water without the use of electricity, fans or pumps), and humanthermal comfortbased onheat index,psychrometricsandenthalpycontrol for buildings to be inhabited by humans or animals,sunrooms, solariums, andgreenhousesfor raising plants.Specific attention is divided into: the site, location and solar orientation of the building, localsun path, the prevailing level ofinsolation(latitude/ sunshine / clouds /precipitation (meteorology)), design and construction quality / materials, placement / size / type of windows and walls, and incorporation of solar-energy-storingthermal masswithheat capacity.While these considerations may be directed toward any building, achieving an ideal optimized cost / performance solution requires careful,holistic,system integrationengineeringof these scientific principles.Modern refinementsthrough computer modeling (such as the comprehensive U.S. Department of Energy "Energy Plus"[3]energy simulation software), and application of decades of lessons learned (since the 1970s energy crisis) can achieve significant energy savings and reduction of environmental damage, without sacrificing functionality or aesthetics.[4]In fact, passive-solar design features such as a greenhouse / sunroom / solarium can greatly enhance the livability, daylight, views, and value of a home, at a low cost per unit of space.Much has been learned about passive solar building design since the 1970s energy crisis. Many unscientific, intuition-based expensive construction experiments have attempted and failed to achievezero energy- the total elimination of heating-and-cooling energy bills.Passive solar building construction may not be difficult or expensive (using off-the-shelf existing materials and technology), but the scientific passive solar building design is a non-trivial engineering effort that requires significant study of previous counter-intuitive lessons learned, and time to enter, evaluate, and iteratively refine the computer simulation input and output.One of the most useful post-construction evaluation tools has been the use ofthermographyusing digitalthermal imaging camerasfor a formal quantitative scientificenergy audit. Thermal imaging can be used to document areas of poor thermal performance such as the negative thermal impact of roof-angled glass or a skylight on a cold winter night or hot summer day.The scientific lessons learned over the last three decades have been captured in sophisticated comprehensive energy simulation computer software systems (like U.S. DOE Energy Plus,et al.).Scientific passive solar building design with quantitativecost benefitproduct optimizationis not easy for a novice. The level of complexity has resulted in ongoing bad-architecture, and many intuition-based, unscientific construction experiments that disappoint their designers and waste a significant portion of their construction budget on inappropriate ideas.The economic motivation for scientific design and engineering is significant. If it had been applied comprehensively to new building construction beginning in 1980 (based on 1970's lessons learned), America could be saving over $250,000,000 per year on expensive energy and related pollution today.[citation needed]Since 1979, Passive Solar Building Design has been a critical element of achievingzero energyby educational institution experiments, and governments around the world, including the U.S. Department of Energy, and the energy research scientists that they have supported for decades. Thecost effectiveproof of conceptwas established decades ago, butcultural assimilationinto architecture, construction trades, and building-ownerdecision makinghas been very slow and difficult to change.[citation needed]The new terms "Architectural Science" and "Architectural Technology" are being added to some schools of Architecture, with a future goal of teaching the above scientific and energy-engineering principles.[citation needed]The solar path in passive design[edit]

Solar altitude over a year; latitude based onNew York,New YorkMain articles:Sun pathandPosition of the SunThe ability to achieve these goals simultaneously is fundamentally dependent on the seasonal variations in the sun's path throughout the day.This occurs as a result of theinclinationof the Earth's axis of rotation in relation to itsorbit. Thesun pathis unique for any given latitude.In Northern Hemisphere non-tropical latitudes farther than 23.5 degrees from the equator: The sun will reach itshighest pointtoward the South in the Northern Hemisphere and the North in the Southern Hemisphere (in the direction of the equator) As wintersolsticeapproaches, theangleat which the sunrisesandsetsprogressively moves further toward the South and the daylight hours will become shorter The opposite is noted in summer where the sun will rise and set further toward the North and the daylight hours will lengthen[5]The converse is observed in the Southern Hemisphere, but the sun rises to the east and sets toward the west regardless of which hemisphere you are in.In equatorial regions at less than 23.5 degrees, the position of the sun atsolar noonwill oscillate from north to south and back again during the year.[6]In regions closer than 23.5 degrees from either north-or-south pole, during summer the sun will trace a complete circle in the sky without setting whilst it will never appear above the horizon six months later, during the height of winter.[7]The 47-degree difference in the altitude of the sun atsolar noonbetween winter and summer forms the basis of passive solar design. This information is combined with local climatic data (degree day) heating and cooling requirements to determine at what time of the year solar gain will be beneficial forthermal comfort, and when it should be blocked with shading. By strategic placement of items such as glazing and shading devices, the percent of solar gain entering a building can be controlled throughout the year.Onepassive solarsun path design problem is that although the sun is in the same relative position six weeks before, and six weeks after, the solstice, due to "thermal lag" from thethermal massof the Earth, the temperature and solar gain requirements are quite different before and after the summer or winter solstice. Movable shutters, shades, shade screens, or window quilts can accommodate day-to-day and hour-to-hour solar gain and insulation requirements.Careful arrangement of rooms completes the passive solar design. A common recommendation for residential dwellings is to place living areas facing solar noon and sleeping quarters on the opposite side.[8]Aheliodonis a traditional movable light device used by architects and designers to help model sun path effects. In modern times, 3D computer graphics can visually simulate this data, and calculate performance predictions.[4]Passive solar thermodynamic principles[edit]Personalthermal comfortis a function of personal health factors (medical, psychological, sociological and situational), ambient air temperature,mean radiant temperature, air movement (wind chill,turbulence) andrelative humidity(affecting humanevaporativecooling).Heat transferin buildings occurs throughconvection,conduction, andthermal radiationthrough roof, walls, floor and windows.[9]Convective heat transfer[edit]Convective heat transfercan be beneficial or detrimental. Uncontrolled air infiltration from poorweatherization/ weatherstripping / draft-proofing can contribute up to 40% of heat loss during winter;[10]however, strategic placement of operable windows or vents can enhance convection, cross-ventilation, and summer cooling when the outside air is of a comfortable temperature andrelative humidity.[11]Filteredenergy recovery ventilationsystems may be useful to eliminate undesirable humidity, dust, pollen, and microorganisms in unfiltered ventilation air.Natural convection causingrisingwarm air and falling cooler air can result in an uneven stratification of heat. This may cause uncomfortable variations in temperature in the upper and lower conditioned space, serve as a method of venting hot air, or be designed in as a natural-convection air-flow loop forpassive solarheat distribution and temperature equalization. Natural human cooling byperspirationandevaporationmay be facilitated through natural or forced convective air movement by fans, but ceiling fans can disturb the stratified insulating air layers at the top of a room, and accelerate heat transfer from a hot attic, or through nearby windows. In addition, highrelative humidityinhibits evaporative cooling by humans.Radiative heat transfer[edit]The main source ofheat transferisradiant energy, and the primary source is the sun. Solar radiation occurs predominantly through the roof and windows (but also through walls).Thermal radiationmoves from a warmer surface to a cooler one. Roofs receive the majority of the solar radiation delivered to a house. Acool roof, orgreen roofin addition to aradiant barriercan help prevent your attic from becoming hotter than the peak summer outdoor air temperature[12](seealbedo,absorptivity,emissivity, andreflectivity).Windows are a ready and predictable site forthermal radiation.[13]Energy from radiation can move into a window in the day time, and out of the same window at night. Radiation usesphotonsto transmitelectromagnetic wavesthrough a vacuum, or translucent medium. Solar heat gain can be significant even on cold clear days. Solar heat gain through windows can be reduced byinsulated glazing, shading, and orientation. Windows are particularly difficult to insulate compared to roof and walls.Convective heat transferthrough and aroundwindow coveringsalso degrade its insulation properties.[13]When shading windows, external shading is more effective at reducing heat gain than internalwindow coverings.[13]Western and eastern sun can provide warmth and lighting, but are vulnerable to overheating in summer if not shaded. In contrast, the low midday sun readily admits light and warmth during the winter, but can be easily shaded with appropriate length overhangs or angled louvres during summer and leaf bearing summer shade trees which shed their leaves in the fall. The amount of radiant heat received is related to the locationlatitude,altitude,cloud cover, and seasonal / hourlyangle of incidence(seeSun pathandLambert's cosine law).Another passive solar design principle is that thermal energy can bestoredin certain building materials and released again when heat gain eases to stabilizediurnal(day/night) temperature variations. The complex interaction ofthermodynamicprinciples can becounterintuitivefor first-time designers. Precisecomputer modelingcan help avoid costly construction experiments.Site specific considerations during design[edit] Latitude,sun path, andinsolation(sunshine) Seasonal variations in solar gain e.g. cooling orheating degree days, solarinsolation,humidity Diurnalvariations in temperature Micro-climatedetails related to breezes, humidity, vegetation and land contour Obstructions / Over-shadowing - to solar gain or local cross-windsDesign elements for residential buildings in temperate climates[edit] Placement of room-types, internal doors & walls, & equipment in the house. Orienting the building to face the equator (or a few degrees to the East to capture the morning sun)[8] Extending the building dimension along the east/west axis Adequately sizing windows to face the midday sun in the winter, and be shaded in the summer. Minimising windows on other sides, especially western windows[13] Erecting correctly sized, latitude-specific roof overhangs,[14]or shading elements (shrubbery, trees, trellises, fences, shutters, etc.)[15] Using the appropriate amount and type ofinsulationincluding radiant barriers and bulk insulation to minimise seasonal excessive heat gain or loss Usingthermal massto store excess solar energy during the winter day (which is then re-radiated during the night)[16]The precise amount of equator-facing glass and thermal mass should be based on careful consideration of latitude, altitude, climatic conditions, and heating/coolingdegree dayrequirements.Factors that can degrade thermal performance: Deviation from ideal orientation and north/south/east/west aspect ratio Excessive glass area ('over-glazing') resulting in overheating (also resulting in glare and fading of soft furnishings) and heat loss when ambient air temperatures fall Installing glazing where solar gain during the day and thermal losses during the night cannot be controlled easily e.g. West-facing, angled glazing, skylights[17] Thermal losses through non-insulated or unprotected glazing Lack of adequate shading during seasonal periods of high solar gain (especially on the West wall) Incorrect application ofthermal massto modulate daily temperature variations Open staircases leading to unequal distribution of warm air between upper and lower floors as warm air rises High building surface area to volume - Too many corners Inadequateweatherizationleading to high air infiltration Lack of, or incorrectly installed,radiant barriersduring the hot season. (See alsocool roofandgreen roof) Insulation materialsthat are not matched to the main mode of heat transfer (e.g. undesirable convective/conductive/radiantheat transfer)Efficiency and economics of passive solar heating[edit]Technically, PSH is highly efficient. Direct-gain systems can utilize (i.e. convert into "useful" heat) 65-70% of the energy of solar radiation that strikes the aperture or collector.Passive solar fraction (PSF) is the percentage of the required heat load met by PSH and hence represents potential reduction in heating costs. RETScreen International has reported a PSF of 20-50%. Within the field ofsustainability, energy conservation even of the order of 15% is considered substantial.Other sources report the following PSFs: 5-25% for modest systems 40% for "highly optimized" systems Up to 75% for "very intense" systemsIn favorable climates such as the southwest United States, highly optimized systems can exceed 75% PSF.[18]For more information seeSolar Air HeatKey passive solar building design concepts[edit]There are six primary passive solar energy configurations:[19] directsolar gain indirect solar gain isolated solar gain heat storage insulation and glazing passive coolingDirect solar gain[edit]Direct gain attempts to control the amount of directsolar radiationreaching the living space. This direct solar gain is a critical part of passive solar house designation as it imparts to a direct gain.The cost effectiveness of these configurations are currently being investigated in great detail and are demonstrating promising results.[20]Indirect solar gain[edit]Indirect gain attempts to control solar radiation reaching an area adjacent but not part of the living space. Heat enters the building through windows and is captured and stored inthermal mass(e.g. water tank, masonry wall) and slowly transmitted indirectly to the building throughconductionandconvection. Efficiency can suffer from slow response (thermal lag) and heat losses at night. Other issues include the cost ofinsulated glazingand developing effective systems to redistribute heat throughout the living area.Isolated solar gain[edit]Isolated gain involves utilizing solar energy to passively move heat from or to the living space using a fluid, such as water or air by natural convection or forcedconvection. Heat gain can occur through a sunspace,solariumor solar closet. These areas may also be employed usefully as a greenhouse or drying cabinet. An equator-side sun room may have its exterior windows higher than the windows between the sun room and the interior living space, to allow the low winter sun to penetrate to the cold side of adjacent rooms. Glass placement and overhangs prevent solar gain during the summer.Earth cooling tubesor otherpassive coolingtechniques can keep a solarium cool in the summer.Measures should be taken to reduce heat loss at night e.g. window coverings or movable window insulationExamples: Thermosiphon Barra system Double envelope house Thermal buffer zone[21] Solar space heatingsystem Solar chimneyHeat storage[edit]The sun doesn't shine all the time. Heat storage, orthermal mass, keeps the building warm when the sun can't heat it.In diurnal solar houses, the storage is designed for one or a few days. The usual method is a custom-constructed thermal mass. This includes aTrombe wall, a ventilated concrete floor, a cistern, water wall or roof pond. It is also feasible to use the thermal mass of the earth itself, either as-is or by incorporation into the structure by banking or using rammed earth as a structural medium.[22]In subarctic areas, or areas that have long terms without solar gain (e.g. weeks of freezing fog), purpose-built thermal mass is very expensive. Don Stephens pioneered an experimental technique to use the ground as thermal mass large enough for annualized heat storage. His designs run an isolated thermosiphon 3m under a house, and insulate the ground with a 6m waterproof skirt.[23]Insulation[edit]Main article:Building insulationThermal insulationorsuperinsulation(type, placement and amount) reduces unwanted leakage of heat.[9]Some passive buildings are actuallyconstructed of insulation.Special glazing systems and window coverings[edit]Main articles:Insulated glazingandWindow coveringThe effectiveness of directsolar gainsystems is significantly enhanced by insulative (e.g.double glazing), spectrally selective glazing (low-e), or movable window insulation (window quilts, bifold interior insulation shutters, shades, etc.).[24]Generally, Equator-facing windows should not employ glazing coatings that inhibit solar gain.There is extensive use of super-insulated windows in theGermanPassive Housestandard. Selection of different spectrally selective window coating depends on the ratio of heating versus coolingdegree daysfor the design location.Glazing selection[edit]Equator-facing glass[edit]The requirement for vertical equator-facing glass is different from the other three sides of a building.Reflective window coatingsand multiple panes of glass can reduce useful solar gain. However, direct-gain systems are more dependent ondouble or triple glazingto reduce heat loss. Indirect-gain and isolated-gain configurations may still be able to function effectively with only single-pane glazing. Nevertheless, the optimal cost-effective solution is both location and system dependent.Roof-angle glass / Skylights[edit]Skylights admit harsh direct overhead sunlight and glare[25]either horizontally (a flat roof) or pitched at the same angle as the roof slope. In some cases, horizontal skylights are used with reflectors to increase the intensity of solar radiation (and harsh glare), depending on the roofangle of incidence. When the winter sun is low on the horizon, most solar radiation reflects off of roof angled glass ( theangle of incidenceis nearly parallel to roof-angled glass morning and afternoon ). When the summer sun is high, it is nearly perpendicular to roof-angled glass, which maximizes solar gain at the wrong time of year, and acts like a solar furnace. Skylights should be covered and well-insulated to reducenatural convection( warm air rising ) heat loss on cold winter nights, and intense solar heat gain during hot spring/summer/fall days.The equator-facing side of a building is south in the northern hemisphere, and north in the southern hemisphere. Skylights on roofs that face away from the equator provide mostly indirect illumination, except for summer days when the sun rises on the non-equator side of the building (depending onlatitude). Skylights on east-facing roofs provide maximum direct light and solar heat gain in the summer morning. West-facing skylights provide afternoon sunlight and heat gain during the hottest part of the day.Some skylights have expensive glazing that partially reduces summer solar heat gain, while still allowing some visible light transmission. However, if visible light can pass through it, so can some radiant heat gain (they are bothelectromagnetic radiationwaves.You can partially reduce some of the unwanted roof-angled-glazing summer solar heat gain by installing a skylight in the shade ofdeciduous(leaf-shedding) trees, or by adding a movable insulated opaque window covering on the inside or outside of the skylight. This would eliminate the daylight benefit in the summer. If tree limbs hang over a roof, they will increase problems with leaves in rain gutters, possibly cause roof-damaging ice dams, shorten roof life, and provide an easier path for pests to enter your attic. Leaves and twigs on skylights are unappealing, difficult to clean, and can increase the glazing breakage risk in wind storms."Sawtooth roof glazing" with vertical-glass-only can bring some of the passive solar building design benefits into the core of a commercial or industrial building, without the need for any roof-angled glass or skylights.Skylights provide daylight. The only view they provide is essentially straight up in most applications. Well-insulatedlight tubescan bring daylight into northern rooms, without using a skylight. A passive-solar greenhouse provides abundant daylight for the equator-side of the building.Infraredthermographycolor thermal imaging cameras ( used in formalenergy audits) can quickly document the negative thermal impact of roof-angled glass or a skylight on a cold winter night or hot summer day.The U.S. Department of Energy states: "vertical glazing is the overall best option for sunspaces."[26]Roof-angled glass and sidewall glass are not recommended for passive solar sunspaces.The U.S. DOE explains drawbacks to roof-angled glazing: Glass and plastic have little structural strength. When installed vertically, glass (or plastic) bears its own weight because only a small area (the top edge of the glazing) is subject to gravity. As the glass tilts off the vertical axis, however, an increased area (now the sloped cross-section) of the glazing has to bear the force of gravity. Glass is also brittle; it does not flex much before breaking. To counteract this, you usually must increase the thickness of the glazing or increase the number of structural supports to hold the glazing. Both increase overall cost, and the latter will reduce the amount of solar gain into the sunspace.Another common problem with sloped glazing is its increased exposure to the weather. It is difficult to maintain a good seal on roof-angled glass in intense sunlight. Hail, sleet, snow, and wind may cause material failure. For occupant safety, regulatory agencies usually require sloped glass to be made of safety glass, laminated, or a combination thereof, which reduce solar gain potential. Most of the roof-angled glass on the Crowne Plaza Hotel Orlando Airport sunspace was destroyed in a single windstorm. Roof-angled glass increases construction cost, and can increase insurance premiums. Vertical glass is less susceptible to weather damage than roof-angled glass.It is difficult to control solar heat gain in a sunspace with sloped glazing during the summer and even during the middle of a mild and sunny winter day. Skylights are the antithesis ofzero energy buildingPassive Solar Cooling in climates with an air conditioning requirement.Angle of incident radiation[edit]The amount of solar gain transmitted through glass is also affected by the angle of the incidentsolar radiation.Sunlightstriking glass within 20 degrees ofperpendicularis mostly transmitted through the glass, whereas sunlight at more than 35 degrees from perpendicular is mostlyreflected[27]All of these factors can be modeled more precisely with a photographiclight meterand aheliodonoroptical bench, which can quantify the ratio ofreflectivitytotransmissivity, based onangle of incidence.Alternatively,passive solarcomputer software can determine the impact ofsun path, and cooling-and-heatingdegree daysonenergyperformance. Regional climatic conditions are often available from local weather services.Operable shading and insulation devices[edit]A design with too much equator-facing glass can result in excessive winter, spring, or fall day heating, uncomfortably bright living spaces at certain times of the year, and excessive heat transfer on winter nights and summer days.Although the sun is at the same altitude 6-weeks before and after the solstice, the heating and cooling requirements before and after the solstice are significantly different. Heat storage on the Earth's surface causes "thermal lag." Variable cloud cover influences solar gain potential. This means that latitude-specific fixed window overhangs, while important, are not a complete seasonal solar gain control solution.Control mechanisms (such as manual-or-motorized interior insulated drapes, shutters, exterior roll-down shade screens, or retractable awnings) can compensate for differences caused by thermal lag or cloud cover, and help control daily / hourly solar gain requirement variations.Home automationsystems that monitor temperature, sunlight, time of day, and room occupancy can precisely control motorized window-shading-and-insulation devices.Exterior colors reflecting - absorbing[edit]Materials and colors can be chosen to reflect or absorbsolar thermal energy. Using information on aColorforelectromagnetic radiationto determine itsthermal radiationproperties of reflection or absorption can assist the choices.SeeLawrence Berkeley National Laboratory and Oak Ridge National Laboratory:"Cool Colors"Landscaping and gardens[edit]Main article:Energy-efficient landscapingEnergy-efficient landscapingmaterials for careful passive solar choices includehardscapebuilding material and "softscape"plants. The use oflandscape designprinciples for selection oftrees,hedges, andtrellis-pergolafeatures withvines; all can be used to create summer shading. For winter solar gain it is desirable to usedeciduousplants that drop their leaves in the autumn gives year round passive solar benefits. Non-deciduousevergreenshrubsand trees can bewindbreaks, at variable heights and distances, to create protection and shelter from winterwind chill.Xeriscapingwith 'mature size appropriate'native speciesof-anddrought tolerant plants,drip irrigation, mulching, andorganic gardeningpractices reduce or eliminate the need for energy-and-water-intensiveirrigation, gas powered garden equipment, and reduces the landfill waste footprint. Solar poweredlandscape lightingand fountain pumps, and coveredswimming poolsandplunge poolswithsolar water heaterscan reduce the impact of such amenities. Sustainable gardening Sustainable landscaping Sustainable landscape architectureOther passive solar principles[edit]Passive solar lighting[edit]Main article:Passive solar lightingPassive solar lightingtechniques enhance taking advantage ofnaturalilluminationfor interiors, and so reduce reliance on artificial lighting systems.This can be achieved by careful building design, orientation, and placement of window sections to collect light. Other creative solutions involve the use of reflecting surfaces to admit daylight into the interior of a building. Window sections should be adequately sized, and to avoidover-illuminationcan be shielded with aBrise soleil,awnings, well placed trees, glass coatings, and other passive and active devices.[19]Another major issue for manywindowsystems is that they can be potentially vulnerable sites of excessive thermal gain or heat loss. Whilst high mountedclerestorywindow and traditionalskylightscan introduce daylight in poorly oriented sections of a building, unwanted heat transfer may be hard to control.[28][29]Thus, energy that is saved by reducing artificial lighting is often more than offset by the energy required for operatingHVACsystems to maintainthermal comfort.Various methods can be employed to address this including but not limited towindow coverings,insulated glazingand novel materials such asaerogelsemi-transparent insulation,optical fiberembedded in walls or roof, orhybrid solar lighting at Oak Ridge National Laboratory.Interior reflecting[edit]Reflecting elements, from active andpassive daylightingcollectors, such aslight shelves, lighter wall and floor colors,mirroredwall sections, interior walls with upper glass panels, and clear or translucent glassed hingeddoorsandsliding glass doorstake the captured light and passively reflect it further inside. The light can be from passive windows or skylights and solarlight tubesor fromactive daylightingsources. In traditionalJapanese architecturetheShjisliding panel doors, with translucentWashiscreens, are an original precedent.International style,ModernistandMid-century modernarchitecturewere earlier innovators of this passive penetration and reflection in industrial, commercial, and residential applications.Passive solar water heating[edit]Main article:Solar hot waterThere are many ways to usesolar thermal energyto heat water for domestic use. Different active-and-passivesolar hot watertechnologies have different location-specific economiccost benefit analysisimplications.Fundamental passive solar hot water heating involves no pumps or anything electrical. It is very cost effective in climates that do not have lengthy sub-freezing, or very-cloudy, weather conditions. Other active solar water heating technologies, etc. may be more appropriate for some locations.It is possible to have active solar hot water which is also capable of being "off grid" and qualifies as sustainable. This is done by the use of a photovoltaic cell which uses energy from the sun to power the pumps.[citation needed]Comparison to the Passive House standard in Europe[edit]Main article:Passive houseThere is growing momentum in Europe for the approach espoused by thePassive House(Passivhausin German) Institute in Germany. Rather than relying solely on traditional passive solar design techniques, this approach seeks to make use of all passive sources of heat, minimises energy usage, and emphasises the need for high levels of insulation reinforced by meticulous attention to detail in order to address thermal bridging and cold air infiltration. Most of the buildings built to the Passive House standard also incorporate an activeheat recovery ventilationunit with or without a small (typically 1kW) incorporated heating component.The energy design of Passive House buildings is developed using a spreadsheet-based modeling tool called the Passive House Planning Package (PHPP) which is updated periodically. The current version is PHPP2007, where 2007 is the year of issue. A building may be certified as a 'Passive House' when it can be shown that it meets certain criteria, the most important being that the annual specific heat demand for the house should not exceed 15kWh/m2a.Design tools[edit]Traditionally aheliodonwas used to simulate the altitude and azimuth of the sun shining on a model building at any time of any day of the year.[30]In modern times, computer programs can model this phenomenon and integrate local climate data (including site impacts such asovershadowingand physical obstructions) to predict the solar gain potential for a particular building design over the course of a year.GPS-basedsmartphoneapplications can now do this inexpensively on a hand held device. These tools provide the passive solar designer the ability to evaluate local conditions, design elements and orientation prior to construction. Energy performance optimization normally requires an iterative-refinement design-and-evaluate process. There is no such thing as a "one-size-fits-all" universal passive solar building design that would work well in all locations.Levels of application[edit]Pragmatic[edit]Many detached suburban houses can achieve reductions in heating expense without obvious changes to their appearance, comfort or usability.[31]This is done using good siting and window positioning, small amounts of thermal mass, with good-but-conventional insulation, weatherization, and an occasional supplementary heat source, such as a central radiator connected to a (solar) water heater. Sunrays may fall on a wall during the daytime and raise the temperature of itsthermal mass. This will thenradiateheat into the building in the evening. This can be a problem in the summer, especially on western walls in areas with high degree day cooling requirements. External shading, or a radiant barrier plus air gap, may be used to reduce undesirable summer solar gain.Annualised[edit]An extension of the "passive solar" approach to seasonal solar capture and storage of heat and cooling. These designs attempt to capture warm-season solar heat, and convey it to aseasonal thermal storefor use months later during the cold season ("annualised passive solar.") Increased storage is achieved by employing large amounts of thermal mass orearth coupling. Anecdotal reports suggest they can be effective but no formal study has been conducted to demonstrate their superiority. The approach also can move cooling into the warm season.Examples: Passive Annual Heat Storage(PAHS) - by John Hait Annualized Geothermal Solar(AGS) heating - by Don Stephen Earthed-roofMinimum machinery[edit]A "purely passive" solar-heated house would have no mechanical furnace unit, relying instead on energy captured from sunshine, only supplemented by "incidental" heat energy given off by lights, computers, and other task-specific appliances (such as those for cooking, entertainment, etc.), showering, people and pets. The use of natural convection air currents (rather than mechanical devices such as fans) to circulate air is related, though not strictly solar design.Passive solar building design sometimes uses limited electrical and mechanical controls to operate dampers, insulating shutters, shades, awnings, or reflectors. Some systems enlist small fans or solar-heated chimneys to improve convective air-flow. A reasonable way to analyse these systems is by measuring theircoefficient of performance. A heat pump might use 1 J for every 4 J it delivers giving a COP of 4. A system that only uses a 30 W fan to more-evenly distribute 10kW of solar heat through an entire house would have a COP of 300.Zero Energy Building[edit]Passive solar building design is often a foundational element of a cost-effectivezero energy building.[32][33]Although a ZEB uses multiple passive solar building design concepts, a ZEB is usually not purely passive, having active mechanical renewable energy generation systems such as:wind turbine,photovoltaics,micro hydro,geothermal, and other emerging alternative energy sources.See also[edit]Renewable energy portal

Energy portal

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Architecture 2030 Daylighting Energy plus house List of low-energy building techniques List of pioneering solar buildings Low energy building Low-energy house Earthship PlusEnergy Solar architecture The 2010 ImperativeEnergy Rating systems House Energy Rating(Aust.) Home energy rating(USA) EnerGuide(Canada) National Home Energy Rating(UK)References[edit]1. Jump up^Doerr, Thomas(2012).Passive Solar Simplified(1st ed.). Retrieved October 24, 2012.2. Jump up^"U.S. Department of Energy - Energy Efficiency and Renewable Energy - Passive Solar Building Design". Retrieved 2011-03-27.3. Jump up^"U.S. Department of Energy - Energy Efficiency and Renewable Energy - Energy Plus Energy Simulation Software". Retrieved 2011-03-27.4. ^Jump up to:ab"Rating tools". Archived fromthe originalon September 30, 2007. Retrieved 2011-11-03.5. Jump up^http://www.srrb.noaa.gov/highlights/sunrise/fig5_40n.gif6. Jump up^http://www.srrb.noaa.gov/highlights/sunrise/fig5_0n.gif7. Jump up^http://www.srrb.noaa.gov/highlights/sunrise/fig5_90n.gif8. ^Jump up to:abYour Home - Orientation9. ^Jump up to:abYour Home - Insulation10. Jump up^"BERC - Airtightness". Ornl.gov. 2004-05-26. Retrieved 2010-03-16.11. Jump up^Your Home - Passive Cooling12. Jump up^"EERE Radiant Barriers". Eere.energy.gov. 2009-05-28. Retrieved 2010-03-16.13. ^Jump up to:abcd"Glazing". Archived fromthe originalon December 15, 2007. Retrieved 2011-11-03.14. Jump up^Springer, John L. (December 1954)."The 'Big Piece' Way to Build".Popular Science165(6): 157.15. Jump up^Your Home - Shading16. Jump up^Your Home - Thermal Mass17. Jump up^"Introductory Passive Solar Energy Technology Overview". U.S. DOE - ORNL Passive Solar Workshop. Retrieved 2007-12-23.18. Jump up^"Passive Solar Design". New Mexico Solar Association.19. ^Jump up to:abChiras, D. The Solar House: Passive Heating and Cooling. Chelsea Green Publishing Company; 2002.20. Jump up^"Zero Energy Buildings". Fsec.ucf.edu. Retrieved 2010-03-16.21. Jump up^"Two Small Delta Ts Are Better Than One Large Delta T". Zero Energy Design. Retrieved 2007-12-23.22. Jump up^Earthships23. Jump up^Annualized Geo-Solar Heating, Don Stephens- Accessed 2009-02-0524. Jump up^Shurcliff, William A..Thermal Shutters & Shades - Over 100 Schemes for Reducing Heat Loss through Windows 1980.ISBN0-931790-14-X.25. Jump up^"Florida Solar Energy Center - Skylights". Retrieved 2011-03-29.26. Jump up^"U.S. Department of Energy - Energy Efficiency and Renewable Energy - Sunspace Orientation and Glazing Angles". Retrieved 2011-03-28.27. Jump up^"Solar Heat Gain Through Glass". Irc.nrc-cnrc.gc.ca. 2010-03-08. Retrieved 2010-03-16.28. Jump up^"[ARCHIVED CONTENT] Insulating and heating your home efficiently: Directgov - Environment and greener living". Direct.gov.uk. Retrieved 2010-03-16.29. Jump up^"Reduce Your Heating Bills This Winter - Overlooked Sources of Heat Loss in the Home". Allwoodwork.com. 2003-02-14. Retrieved 2010-03-16.30. Jump up^[1][dead link]31. Jump up^"Industrial Technologies Program: Industrial Distributed Energy". Eere.energy.gov. Retrieved 2010-03-16.32. Jump up^"Cold-Climate Case Study for Affordable Zero Energy Homes: Preprint"(PDF). Retrieved 2010-03-16.33. Jump up^"Zero Energy Homes: A Brief Primer"(PDF). Retrieved 2010-03-16.External links[edit] www.solarbuildings.ca- Canadian Solar Buildings Research Network www.eere.energy.gov- US Department of Energy (DOE) Guidelines www.climatechange.gov.au- Australian Dept of Climate Change and Energy Efficiency www.ornl.gov- Oak Ridge National Laboratory (ORNL) Building Technology www.FSEC.UCF.edu- Florida Solar Energy Center www.ZeroEnergyDesign.com- 28 Years of Passive Solar Building Design [2]- Prefabricated Passive Solar Home Kits Passive Solar Design Guidelines http://www.solaroof.org/wiki www.PassiveSolarEnergy.info- Passive Solar Energy Technology Overview www.yourhome.gov.au/technical/index.html- Your Home Technical Manual developed by the Commonwealth of Australia to provide information about how to design, build and live in environmentally sustainable homes. amergin.tippinst.ie/downloadsEnergyArchhtml.html- Energy in Architecture, The European Passive Solar Handbook, Goulding J.R, Owen Lewis J, Steemers Theo C, Sponsored by the European Commission, published by Batsford 1986, reprinted 1993[show]Error: Page does not existDesign

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Home Site Analysis Site Use Passive Design Controlling temperature with passive design: an introduction Location, orientation and layout Insulation Thermal mass Shading Ventilation Daylighting Glazing and glazing units Controlling indoor air quality Controlling noise Climate change Water Material Use Energy Wet Areas Health and Safety Other Resources

Passive DesignDesigning the building and the spaces within it to benefit from natural light, ventilation and even temperatures. Passive DesignPassive design is the key to sustainable building.It responds to local climate and site conditions to maximise building users comfort and health while minimising energy use.It achieves this by using free, renewable sources of energy such as sun and wind to provide household heating, cooling, ventilation and lighting, thereby reducing or removing the need for mechanical heating or cooling. Using passive design can reduce temperature fluctuations, improve indoor air quality and make a home drier and more enjoyable to live in.It can also reduce energy use and environmental impacts such as greenhouse gas emissions.Interest in passive design has grown, particularly in the last decade or so, as part of a movement towards more comfortable and resource-efficient buildings.Key features of passive designThe key elements of passive design are: building location and orientation on the site; building layout; window design; insulation (including window insulation); thermal mass; shading; and ventilation. Each of these elements works with others to achieve comfortable temperatures and good indoor air quality.The first step is to achieve the right amount of solar access enough to provide warmth during cooler months but prevent overheating in summer. This is done through a combination of location and orientation, room layout, window design and shading.Insulation and thermal mass help to maintain even temperatures, while ventilation provides passive cooling as well as improving indoor air quality.All of these elements work alongside each other and therefore should be considered holistically. For example, large windows that admit high levels of natural light might also result in excessive heat gain, especially if they cast light on an area of thermal mass. Similarly, opening windows that provide ventilation will also let in noise.Alongside passive design features, designers should also consider other factors such as views, covenants and local authority restrictions, and building owners preferences.Passive design in new and existing buildingsIt costs little or nothing to incorporate passive design into a new building. The benefits are greatest when passive design principles are incorporated into the entire design and build process, from site selection onwards.Once a building is completed, some passive design features can be incorporated during later upgrades for example, insulation can be improved, and it may be possible to alter room layout to improve orientation and solar access.But it may be difficult to achieve the full benefits. For example, it will not be practical to turn a completed house around on the site to take better advantage of sun or cooling breezes. Controlling temperature with passive design: an introduction Location, orientation and layout Insulation Thermal mass Shading Ventilation Daylighting Glazing and glazing units Controlling indoor air quality Controlling noise Climate changeTop of Form

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Bottom of Form Interior Design Housekeeping Entertaining Home Improvement Gardening & Plants Landscaping More eHowFeatured:DIY HomeSimplify the SeasonGadget Guide1. eHow2. Home & Garden3. Building & Remodeling4. Building Materials & Supplies5. Acoustical Properties of Building MaterialsAcoustical Properties of Building MaterialsBy Jagg Xaxx, eHow Contributor Share Print this articleWood is a building material that absorbs sound.It's common to consider the durability, cost and aesthetic appeal of building materials when building a new home, but builders and homeowners often neglect acoustics. A beautiful home can become a headache if sound carries through it too easily, or if every sound has an echo. You can control the acoustics of your new home to some extent by considering what materials to use during the design process. Have a question? Get an answer from a Handyman now!Other People Are Reading Acoustic Properties of Materials List of Acoustic Materials1. Principles Vibrations in the air and in materials carry sound through a room. When these vibrations hit a flat, hard surface, they rebound into the room, causing an echo. When sound waves hit a surface that is susceptible to vibration, the material in the wall transfers the sound into the next room rather than stopping or reflecting it. Thus, a solid concrete room will be prone to echoes while a room framed with wood and sheathed with drywall will not be soundproof. Providing an absorbent, roughly textured surface such as a wall full of books decreases both sound transfer and echoes.Materials Concrete is very effective at reducing sound transfer from one room to another, but will create echoes within a room if left in its natural state. Wood reduces both sound transfer and echoing, unless it is installed in large, flat walls with nothing breaking it up. You can make a hardwood floor more acoustically pleasing by placing a thick wool carpet in the middle to absorb ambient sound. Wool and other carpets, soft and upholstered furniture and textile wall hangings all contribute to an aurally pleasing environment. Echoes Most people have had the experience of walking through a brand new house with nothing in it and listening to the strange echoes. In a lived-in house, the shapes, materials and surfaces break up sound waves and create an environment in which vibrations can't bounce back and forth, which is why you don't hear echoes in your home. If you have large rooms that feature concrete walls, concrete floors and concrete ceiling surfaces and very few possessions, then you may notice echoes.Soundproofing Some types of wall insulation are made specifically for soundproofing. These acoustic batts are installed inside of framed walls in the same way as heat insulation, but are designed to dampen sound vibrations. You can further soundproof walls by sheathing them with plywood and screwing drywall over the plywood. This greatly reduces the vibrational characteristics of the drywall and eliminates sound passing from one room to another. For a truly soundproofed room, build a double row of studs with insulation in between them. Most sound that passes between rooms is carried through the wall studs.Sponsored Links Cochrane ClearVu FencingAnti-cut , Anti-climb Highsecurity fence.Contact Us Today !www.clearvu.com/ INTEK InsulationThermal and Acoustic InsulationFor marine, aircraft and industrytrelleborg.com/appliedtechnology Jobs in Qatar - 2013All new jobs; all categories.Register & apply free!www.bayt.com/jobs-in-qatar Acoustics DesignBuilding AcousticsEnvironmental Noise Controlwww.pps.aeRelated Searches Building Materials Supply Acoustic Sound Panels Acoustical Ceiling Properties of Materials Acoustical WallsTop of FormeHow NowAsk a HandymanAsk our online Handymen get your answers in real time!

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HOME NEWS NOTES OLD QUESTIONS QUESTION SOLUTIONS ARTICLESAcoustical properties of building materialsAPRIL 03, 2013SAJANNO COMMENTSAcoustical properties of building materialsSound it is anything that can be heard. In other words, it is the sensation caused by a vibrating medium acting on the air. Source of sound is most often vibrating solid body. The medium conveying sound to ear can be gas, liquid or solid. It is transmitted as the longitudinal wave motion. i.e. successive compression- rarefaction of molecules. In solid body, the transmission is by lateral motion. Wave length determines pitch of sound. Higher the frequency, higher would be pitch. Frequency is the waves per unit time. Sound is the product of frequency and wave length. Loudness depends on distance from vibrating body.Ranges of hearing frequency are 20 Hz to 20 kHz.1. Infra sound frequency less than 20 Hz2. Audible sound frequency ranges between 20 Hz t- 20kHz3. Ultra sound frequency greater than 20 kHz Reactions produce by sound1. Reflections from walls, floors, ceiling etc.2. Absorption by floors, by ceiling, by furniture etc.3. Transmission to adjacent room Sound classification1. Air borne sound sound through air to air.2. Impact of structure borne sound sound through direct contact, such as footsteps, hammering or vibration etc. it is very sharp and troublesome.AcousticsAcoustic is the science of soundIt assures the optimum conditions for producing and listening to speech and musicThe panning of acoustical design has to provide for dissipation of noise and insulation against soundNoise and its effect1. Annoyance- irritation2. Disturbance of sleep3. Interface of disturbing conversation4. Damage of earMeasurement of annoyance is subjective attitude and depends upon with mental and physical well being of listeners with their experience Magnitude of noise levelTypes of soundsNoise level (dB)Effects

Light road trafficMedium road trafficsHeavy road trafficsRail trafficsAir traffics60-7070-8080-9090-100>130 Physiological effect (annoyance) Physiological effect (annoyance) Prolonged exposure causes permanent hearing loss Prolonged exposure causes damage to auditory organ Causes pain Instantaneous loss of hearing

Defects due to reflected sound1. Echoes2. ReverberationEcho is the reflected sound and heard just after the produced as a repetitionReverberation is the continuous reflection of produced sound waves (reflection, inter-reflection etc) until they are gradually faded outCertain amount of reverberation is necessary to enhance the sound, but excessive is damaging to clarity. Reverberation timeIt is the time taken for sound energy to decay by below annoyance level (60dB) after the sound source has stopped. It depends on, volume of room, absorption in walls roofs and floors etc. it has to be minimized using sound absorbing materials. Sound insulation1. Sound absorption (prevention of reflection)2. Sound insulation (prevention of transmission) Sound absorbents1. Porous materials2. Resonant panel3. Cavity resonators4. Composite typesIn porous materials, the sound waves on striking its surface enter to the pores, vibrate inside and die-out there. Normally these materials are soft and have large pores with interconnected channels.Resonant panels are semi-hard in the form of porous fiber boards that acts as sound absorbent. These boards are fixed on timber frame with air gap between and also with wall backing. In the resonant panels, the sound pressure waves cause vibration and this vibration is absorbed by air gap (space) called damping. Porous materials may also be put in the gap between boards. It is suitable for low frequency waves.Cavity resonators are the chambers with the narrow openings. The absorption of sound takes place in the case by the resonance of air.Composite types are the perforated panels fixed with air space containing porous absorbents. The panels may be of metal, plywood, hard board, plaster board etc. the perforation should be at least 10 percent of area high frequency sounds are absorbed in this perforated panel.

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HOME NEWS NOTES OLD QUESTIONS QUESTION SOLUTIONS ARTICLESNoise control and constructional precautions to reduce noiseAPRIL 05, 2013SAJANNO COMMENTSThe Noise control and constructional precautions to reduce noise are as follows :- General consideration1. Isolate sound source2. Proper orientation of building , i.e. no opening towards noise3. Properly planned rooms in building4. Furnishing materials in room helps sound absorption5. Partitions Ridge and Movable6. Control of impact sound i.e. sue of resilient materials as carpets in floor7. Discontinuing the path of vibration by using sound absorbing materials8. Use of headphones and air plugs in case of high sound. Construction materials1. Wall partitionsAbsorbents in the Wall partitions act as the barriers to air borne sound transmissionTypes Rigid and homogeneous partitionsInsulation in this case depends on the weight of the partition per unit area and increases with thickness.Following table illustrates the insulation properties for different walls.S. No.Types of wallApprox. wt. of wall kg/mAverage sound reduction dB

1.One brick wall plastered in both side49050

2.One and half brick wall plastered in both side71053

3.Cavity (50mm) with half brick in both leaves49050-53

4.Half brick or concrete with plaster both side17045

5.200 mm concrete wall18545

6.Gypsum board partition on timber frame7045

7.75mm hollow clay block with plaster both side36

Hard reflecting surface outside partition increases insulation Partition of porous materialInsulation increase to 10% or higherMaterial may be rigid or flexible Hollow and composite partitionCavity is betterFilling of cavity with resilient material is preferred2.Floors/CeilingsThere is the horizontal barrier to noiseThey act as barrier to airborne an impact sound, but offer poor insulation for structure borne or impact sounds or insulation in floor, resilient surface materials, and floating floors. Resilient surface materials on floorsCotton, wooden, carpets, asphaltmastics,PVCcarpets, corks, etc.Softer the material used greater would be the insulation value Floating floor constructionProvides insulation from any other parts of structureIt is made to rest on float over existing floor by means of resilient materials such as, glass, wool, quilt, hair felt, cork rubber, etc.Impact sound do not transmits.On concrete floor, partition is constructed off the structural floor and it is independentTypes of floating floors Concrete floor with floating concrete screed: it is the PCC of 1:1-5:3 on resilient materials above concrete floor. Concrete floor with floating wooden raft: it is wooden nailed to battens forming raft on resilient quilt (20mm) Heavy concrete floor with soft floor (resilient) finish or covering Wooden floorsIt has the problem of impact sound3.Windows and doorsIt should be- Air tight- Double glazed- Thickness of glass to be increased- Increase weight of shutter4.Insulating sanitary fitting- WC be insulated, pan to rest upon thin pad of felt, cork, rubber, etc.- Cisterns not on wall of bed rooms, brackets be fixed with insulating materials (clips)5.Machine mounting and insulation of machineryMachine resting on resilient materials as steel spring, rubber, corks, etc.Brush holders is a spring is typically used with the brush, to maintain constant contact with the commutator. As the brush and commutator wear down, the spring steadily pushes the brush downwards towards the commutator. Eventually the brush wears small and thin enough that steady contact is no longer possible or it is no longer securely held in the brush holder, and so the brush must be replaced.

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