Paste yo1.NATURAL VENTILATION
Natural ventilation is the process of supplying and removing air from an indoor space by naturally and without the use of a fan or other mechanical system. It uses outdoor air flow caused by pressure differences between the building and its surrounding to provide ventilation and space cooling. The natural way of creating a healthy, comfortable and energy efficient home. Also, removes heat in summer and control moisture in winter.
Ventilation of buildings has been a major cooling technique throughout the world, as it provides cooling by using air to carry heat away from the building convective cooling and or from the human body itself physiological cooling. It is based on the fundamental heat transfer mode of convection, when the air flowing next to a surface carries away heat, provided it is at a lower temperature than the surface. When it passes over the human body, it increases the evaporation rate from the skin and enhances heat extraction.
(Anon., n.d.)
Provided that outdoor climatic conditions are favorable, the use of natural ventilation can reduce the cooling load, enhance thermal comfort conditions, and maintain indoor air quality. The effectiveness of natural ventilation techniques is determined by the prevailing outdoor conditions and microclimate, and the buildings characteristics orientation, windows- number, size, location.
Natural ventilation it can also be improved by cooling of buildings elastic up to 25-50% in energy investments. There are Several old-style construction styles improve with natural ventilation by providing for high ceilings and air spaces at ceiling level or below the eaves to improve the daytime venting of heat and night-time cross ventilation.
Natural ventilation is important in health benefits but necessity is observed to prevent expectable hazards. For example, natural ventilation in locations where outdoor air pollution is better than indoor air pollution might not be helpful. Likewise, ventilation short of screening actions can permit for the entrance of mice that carry diseases in certain environments. And can also be open windows at street level can pose a safety risk in neighborhoods anywhere lawbreaking is a serious issue.
(Anon., n.d.)
(Anon., 2012)
The following chart shows how much these different strategies can extend the comfortable climate range for people.
Figure 1.1 Different cooling strategies can keep people comfortable at different ranges of outside temperature and humidity
1.1 Structural cooling on summer nights
Thermal storage (e.g. concrete floors, masonry walls) can use this structural cooling to keep indoor temperature cooler during the next day. Windows need to offer security while allowing ventilation
Example in summer
Figure1.2 Structural cooling on summer nights
Source: Natural Ventilation in Buildings, Tony Rafael, NEERG seminar, 31 Aug 2006, Windtech Consultants
Good features: ‘Natural method’ with lowest energy consumption and Comfort level is reasonably
Limitations
1. Poor safety margin for warmer days
2. Must pay attention to outside temperature
3. Needs lots of ‘hands-on’ actions
4. Limited parts of the house are comfortable
2.ANCIENT METHODS OF NATURAL VENTILATION
2.1 Importance of natural ventilation
Natural ventilation is a long-lasting air circulating all over the building, though the humidity is huge outside it constantly keeps inside the building comfortable. A natural ventilator does not need any care and there is no fear of the system breaking down.
It always works, rain or shine, day or night, and even if there is a power outage. A natural current will preserve the air circulating constantly. Natural ventilation is self-adjusting. The hotter the air inside, the more airflow there will be. On cooler days, there will be less airflow. Additionally, you’ll never have to turn on an exhaust fan to expel stale.
(Anon., 2012)
It also helps to get a healthy air and it makes the place comfortable to live and exhalation of the hot air is also called as the chimney effect which is essentially the movement of the air in and out of the structure natural ventilation cannot replace the mechanical equipment’s like air cooler Natural ventilation is best practiced in temperatures with consistent breezes and chilled nights.
Out of many ventilation systems natural ventilation is the most efficient one and it doesn’t need any complex structures to get the air the only thing is to fix the doors and the windows in a correct position where the air movement is more it also makes not to worry about ventilation in the summer season also need not worry about energy consumption and electricity bills.
(Anon., n.d.)
2.2 Function of natural ventilation
The three main function of ventilation are:
1. The source of fresh air
2. Physiological cooling
3. Removing heat from, on adding it to
The fresh air required in the building to add sufficient oxygen temperatures, the building inside maintaining comfortable relative humidity (RH) levels and these fresh air systems inhibit extreme air from entering the home to maintain comfortable indoor air temperatures.
Figure 1.3 different between dry climate and humid climate
For natural ventilation, usually certainly limited solutions:
‘ The facility of everlasting ventilators of the opening which cannot be closed may be compulsory.
‘ These also be air bricks into walls or combined with windows.
‘ The size of openable windows may be specified in relation to the floor area or the volume of the room.
(Anon., n.d.)
(Anon., n.d.)
Figure1.4 Mud bricks with holes for opening for use of natural ventilation
2.3 Types of natural ventilation
Natural ventilation is not a new impression it has been used for thousands of years. Using the natural movement of air to control air flow inside of a house can have a countless effect on building conditions and worker relief.
1. Signal side single open
2. Single side dual opening
3. Advanced ventilation
4. Sizing of natural ventilation
5. Window ventilation
6. Cross ventilation
7. Stack/reverse stack ventilation
2.4 signal side signal open
Single side ventilation arises when large ventilation openings such as entries and holes-in-the-wall are situated on one exterior wall only. It also exchanges the air takes place by wind by outward beginnings interrelating with the local external air streams and by local stacks.
Figure1.5 The cooling process in single side opening circulating airflow from inside to outside
Figure 1.6 The cooling process in single side opening circulating airflow from inside to outside
http://www.windowmaster.com/solutions/natural-ventilation/natural-ventilation-strateg
2.5 since sided double opening ventilation
Stack induced flows rise with the vertical parting of the openings and with the inside to outside temperature change. As well as enhancing the ventilation rate the double opening increases the depth of penetration of the fresh air into space, as opposed to single opening ventilation. There are multiple ventilation openings are providing at different sizes and heights inside the front of the ventilation rate can be improved with the stack effect. As a rule of thumb, the limiting depth for effective ventilation is about 2/5 times the floor to ceiling height of a building.
Figure 1.7 Single sided double opening ventilation
Source: July 12, 2007, NATURAL VENTILATION TRICKS TO COOL OFF YOUR SUMMER
Figure 1.8 Single sided double opening ventilation
Source: complicated&psig=AFQjCNHUimQnVePLiDoZFRlD2K6rkyxHcQ&ust=1505279580215554
2.6 wind driven ventilation
The wind-driven naturally occurring the wind blows the building, the breeze successes the windward wall producing a direct positive pressure. The wind accruing around the building and leaves the leeward wall with a negative pressure, also known as a sucking effect. If there are any openings on the windward and leeward walls of the building, fresh air will rush in the windward wall opening and exit the leeward wall opening to balance and relieve the pressures on the windward and leeward walls.
Figure 1.9 Building elevation with wind driven ventilation
Source: h k green technology network
The building shape can create wind pressures that can effectively drive the air flow through the openings of the building. To capture the wind and bring ventilation to the building, the building shape becomes a central factor.
2.7 cross ventilation
The single procedure of breeze freshening is called 'cross ventilation'. It includes wind passing through a vent window or door and letting air to flow straight passing the house and out over an opening on the other side of the home. Knowing which way, the wind is likely to blow where you plan to build is a good way to plan for effective cross ventilation. Similarly, the position and size of your vents, windows, and doors, as well as the path among the different sides of the house, make a big change through effectively you can cross ventilate your home.
It also Allows for a home or building cooling and ventilation there is minimal maintenance and no operating costs. Mainly for new buildings, cross ventilation can be constructed into the building design at minimal cost.
It always requires fully passive cooling no need of energy. Even cross ventilation can also be combined with active mechanical ventilation or passive stack ventilation to lessen the building costs though safeguarding more regular ventilation and cooling
Figure 1.9 Cross ventilation can be extremely effective
Source: http://www.build.com.au/wind-ventilation-and-cross-ventilation
Figure 1.10 Different amounts of ventilation and air mixing with different windows open
In the cross-ventilation insertion inlets low in the room and outlets high in the room can cool spaces more effectively, because they power the natural convection of air. Cooler air sinks lower when the hot air rises hence, locating the opening down low helps push cooler air through space, while locating the exhaust up high helps pull warmer air out of the space
2.8 stack ventilation
There are two kinds of passive ventilation it uses the air pressure change by the height to pull the air through the building with stack ventilation and Bernoulli's principle. Lesser pressures higher in the building help pull air rising. The change between stack ventilation and Bernoulli's principle is where the pressure difference arises after.
Stack ventilation taking advantage of this effect by building openings in the building envelope high at a substantial height it also allows the warm air to escape. The negative pressure at the top of the building draws in colder, denser outside air through openings low in the building. This effect occurs in all buildings, though it is naturally weak. The use of a stack concentrates the effect. Longer typically increase airflow.
Figure 1.11 Lower air pressures at higher heights can passively pull air through a building.
Stack ventilation uses temperature differences to move air. Hot air rises because it is lower pressure. For this reason, it is sometimes called buoyancy ventilation
Figure 1.12 The stack effect: hot air rises due to buoyancy, and its low-pressure sucks in fresh air from outside
Source: Image from Sun, Wind, and Light, by G.Z. Brown and Mark DEKALB published by Wiley
1.3 NIGHT FLUSHING
The process of removing hot air from a building during the cool evening hours, to cool elements with thermal mass within the building and flush stale air.
Night-Purge Ventilation it also keeps spaces and other passive ventilation openings closed during the day, but open at night to flush warm air out of the building and cool thermal mass for the next day. Successful night-purge ventilation is determined by how much heat energy is removed from a building by bringing in night-time air, without using active HVAC cooling and ventilation.
Night-purge ventilation is helpful when daytime air temperatures are so high that bringing unconditioned air into the building would not cool people down, but where night-time air is cool or cold. This strategy can provide passive ventilation in weather that might normally be considered too hot for it.
Figure 1.13 showing night and day ventilation in building
Figure 1.14 During the day, thermal mass soaks up heat; at night, it is cooled by outside air
Source: http://www.passivent.com/night-cooling
Night cooling also refers to the process of natural ventilation at night to purge additional heat and cool the building fabric. A house with sufficient thermal mass it can be exposed to nighttime ventilation it can be reduced least daytime temperatures at 2%-3% by using this kind of approach. Early in the morning, if the building is closed and kept closed during the day to prevent warm outside air from incoming.
Through the day, the cool mass absorbs heat from occupants and other internal loads.by working of night flushing opening pathway of a wind ventilation and stack ventilation at the night to cool the thermal mass of the building this can also be done mainly by radiation but convection and transfer also play people.
Because the "coolth" of night- ventilation is stored in thermal mass this also requires a house with a huge area of exposed to internal thermal mass.by using of natural ventilation for cooling it requires a relatively passable interior to promote air flow. This means not obscuring floors with carpets and coverings, walls with cupboards and panels, or ceilings with acoustic tiles and drop-panels etc.
1.3.1 Natural night flushing
Natural night flushing by opening windows at night, let wind-driven or buoyancy-driven airflow cool the house space and then closing windows during the day.
1.3.2 Mechanical flushing
Mechanical night flushing is forcing the air passes mechanically through the ventilation ducts or pipes at the night at a high air flow rate and supplying air to space during the day at required minimum airflow.
Figure 1.15 Mechanical ventilation in building
Source: https://www.thegreenage.co.uk/mechanical-ventilation-in-buildings-what-you-need-to-know/
1.3.3 Mixed mode night flushing
Mixed-mode night flushing through a grouping of natural ventilation and mechanical ventilation also known as mixed-mode ventilation it can also be using for fans to assist the natural air flow.
1.4 DESIGNING FOR NATURAL VENTILATION
The design for natural ventilation should be included exploiting both the wind and stack driven ventilation design concepts as mentioned above.
General design considerations include:
‘ The increase of air supply consumption by ensuring no outside obstruction like vegetation or site objects nor inside obstruction like furniture and interior partition inlet opening.
‘ All available spaces should be inlet and outlet opening in which at least a minimum of one opening should be an operable window to control flow.
‘ Rooms space should also have inlet and outlets opening placed in opposing pressure zones. This can also be including opening on the windward and leeward walls or on the windward wall and roof.
‘ The long front of the building and major of the opening should be directed so that the windward wall is perpendicular to the summer wind.
‘ By using of skylights or vents to the interior. They may be very desirable for night time thermal comfort in the houses to vent heated or warm air that rises, also allow heat to be radiated into the cold. This can also be good outlets for wind driven ventilation.
‘ It should also be inlets supply air at allocation low in the room. Outlets must be placed across the room and at a higher level.
‘ There should be at least 3m allowance for the floor to the ceiling.
‘ Windows area should also do not excessive and to be protected by exterior shading to the house.
‘ Lessen the possibility of wall warming by the sun through the use of light-colored building exteriors trees/shrubs to afford shading and evaporative cooling, grass and other groundcover to keep ground temperatures low and ponds and fountains to improve evaporative cooling and internal loading should be kept low.
‘ It should also design for high thermal capacity and exposed for the ceiling for a night cooling. Various of the thoughts are taken above is to also increase the airflow or lower the heat gain so that the natural ventilation can effectively cool the spaces in the building.
‘ Mechanical cooling and ventilation systems will be used to supplement the natural ventilation. By lowering the heat gains, the less airflow will be required to remove the heat, thus there will be less a need of a mechanical cooling system.
1.5 HOW MUCH VENTILATION DOES A HEALTHY HOUSE NEEDS
We need ventilation in these areas:
‘ Humidor smelly places (bathrooms, kitchens)
‘ Where there are people living and breathing (family room, bedrooms, etc.)
‘ How much ventilation do we need?
‘ This question does not seem to have a simple answer
‘ Summer (hotter outside than inside)
‘ Good effects:
Movement of air around people (helps with cooling effect ‘ already covered)
Venting of roof space (removes heating effect of hot air above ceiling)
‘ Bad effects:
When external air is too hot for airflow cooling, fresh air flow for health requires energy for cooling
‘ Winter (colder outside than inside)
‘ Good effects:
None (although you do need ventilation for health)
‘ Bad effects:
When external air is cold, fresh air flow for health requires energy for heating
If roof space is ventilated, then potentially useful heat may escape to the atmosphere
Figure 1.16 Winter heating
Figure 1.17 Summer cool
CHAPTER 2- PASSIVE COOLING
2.0 PASSIVE COOLING
Passive cooling is the least expensive means of cooling a house in both economic and environmental terms.it is equal of passive cooling is required in every hot climate at some time of the year all passive cooling plan relays on daily changes in temperature and relative humidity.
Just like passive heating, cooling your building using passive approaches is important for reducing energy usage in your building. Specifically utilizing passive cooling strategies like natural ventilation, air cooling, and shades can reduce your demand for mechanical cooling while maintaining thermal comfort.
As cooling requirements are dictated by climate, distinctly different approaches to passive cooling are required for:
‘ hot humid climates (Zone 1) where no heating is required
‘ temperate and warm climates (Zones 2’6) where both heating and cooling are required
‘ cool and cold climates (Zones 7’8) where heating needs are more important.
‘
2.1 GENERAL PASSIVE COOLING TECHNIQUE
A) SITE LEVEL BUILDING FEATURES
‘ Location
‘ Orientation
‘ Vegetation
‘ Land massing
‘ Microclimate modification
B) ARCHITECTURAL FEATURES
‘ Building exposure
‘ Surface/volume ratio
‘ Screen Shade
‘ Wing walls
‘ Overhangs
C) WEATHER SKIN FEATURES
‘ Insulation
‘ Glazing Mass
‘ Material type
‘ Texture Finishes
2.2 DESIGN OF CLIMATE
Almost 40% of household energy is used for heating and cooling to attain thermal comfort. This amount might be cut to near nil in new housing finished sound climate responsive design and truly should be our ambitious goal. Considering current consumer favorites and industry observers, sharing the rate to 20% is a highly possible in the tiny term.
It is used 40% of the household energy used for heating and cooling to attain thermal comfort could be cut to almost zero in a new housing through complete climate responsive design.
Reducing or removing heating and cooling need to be an existing house is a important test mainly those designed are built earlier building energy efficiency standards were announced, when utilizations were effective but incompetent.it was Based on 1.5% annual regeneration rates, at minimum 50% of our present housing stock will still be in service in 30 years’ time.
The new house constructed nowadays will be in service in future times. after we expect to see important changes in the climate. Designing for today’s climate is important. Confirming that those designs can be just as efficient after 30 years of climate change would be necessary.
Affordability is frequently mentioned as the main barrier to better efficiency but also increasing energy costs are quickly unstable with affordability focus from early or upfront price to continuing or working cost. With this change, high levels of thermal presentation are becoming gradually valued and the repayment or amortization period for thermal performance upgrades is lessening quickly.
2.3 COOLING PEOPLE
The Reasons moving comfort for people (human thermal comfort) are outlined in Design for climate and contain both physiological and psychological factors.
Healthy heat loss is also important, both physiologically and psychologically. It includes direct radiation to cooler exteriors.
It should be operative, passive cooling requirements to cool both the building and the persons in it.
The Evaporation of moisture is the most actual physiological cooling development. It can involve air movement and reasonable to low humidity (less than 60%).
Transmission contributes to together types of comfort and includes body contact with cooler exteriors. It is most real when people are active. (e.g. sleeping on a waterbed)
2.4 COOLING BUILDING
The competence of the building cover can be maximised in several ways to minimise heat gain:
‘ shading windows, walls and roofs from direct solar radiation
‘ using lighter colored roofs to reflect heat
‘ using insulation and buffer zones to minimise conducted and radiated heat gains
‘ making selective or limited use of thermal mass to avoid storing daytime heat gains.
To maximise heat loss, use the following natural sources of cooling:
‘ air movement
‘ cooling breezes
‘ evaporation
‘ earth coupling
‘ reflection of radiation.
2.4.1 Air movement
The most important component of passive cooling is air movement in the building. It also cools persons by increasing evaporation and wants both breeze capture and fans for a holdup in still environments.
Mainly in moving air also conveys heat to powered cooling systems where it is removed by hotness pumps and recirculated. It also chills buildings by carrying hotness out of the building as warmed air and exchanging it with cooler external air. This also requires well-designed openings (windows, doors, and vents) and unrestricted breeze paths.
In all weathers, air movement is useful for cooling people, but it may be less effective during periods of high humidity. An airspeed of 0.5m/s equates to a 3”C drop in temperature at a relative humidity of 50%. This is a one-off physiological cooling effect resulting from heat being drawn from the body to evaporate perspiration. Air movement exposes the skin to dryer air.
Increased air speeds do not increase cooling at lower relative humidity but air speeds up to 1.0m/s can increase evaporative cooling in higher humidity. Air speeds above 1.0m/s usually cause discomfort.
2.4.2 Cool breeze
When the climate provides cooling breezes, maximising their movement finished a home when cooling is required is an important component of the passive design. Unlike cool night air, these breezes incline to occur in the late afternoon or early evening when chilling necessities frequently highest.
Figure 2.1 Airflow in the building at different parts of house
Cool breezes effort best in narrow or open plan layouts.
Cool breezes effort best in narrow or open plan layouts and rely on air-pressure differences produced by wind or breezes.
They are less effective in:
‘ constructions with deep floor plans or separate small rooms.
‘ extended periods of high external temperature (ambient or conducted heat gains above 35’40 watts per square meter (W/m2)
‘ positions with high noise, security risk or poor external air quality, where windows may need to be closed.
Coastal breezes are usually from an aground way (south-east and east to north-east in most east coast areas, and south-west in most west coast areas, e.g. the ‘Fremantle Doctor’).
In mountainous or hilly areas, cool breezes frequently flow down slants and valleys in the late evening and early morning, as a heat radiating to clear night skies cools the land mass and creates cool air currents.
Thermal currents are common in flatter, inland areas, created by daily heating and cooling. They are often of short duration in early morning and evening but with good design can produce valuable cooling benefits.
2.5 NIGHT AIR
The Night air is a Warm air radiating from the building fabric’s thermal mass is changed with cooler night air drawn by internal’external temperature differences slightly than breezes. Cool night air is a reliable source of cooling in inland areas where cool breezes are limited and daytime temperature ranges usually exceed 6’8”C. and Complete height, dual hung windows are ideal for this purpose. Extra cooling can be gained by counting whole of house fans.
2.6 WIND TOWER
Usually, Wind towers are commonly used in Hot Dry weathers for cooling purposes A wind tower is operating in various ways, according to the time of day, and the presence and absence of wind. A pre-required for using wind tower is that the site should experience winds with an equally good and reliable speed. The fundamental principle overdue its process lies in moving the temperature and thus the density of the air in and around the tower. The alteration in density produces a current dragging air either upwards or downwards finished the tower.
Figure 2.2 Wind tower
2.7 INDUCED VENTILATION TECHNIQUES
Encouraged ventilation is caused when there is a compression change among the outside air and air present inside the building. Hot air rises due to lower pressure and pulls the fresh air from adjacent creating flexibility ventilation. This effect is also known as stack ventilation
2.7.1 Air vent
The air ventilation that relies upon to be increased buoyancy of warm air it rises to escape the building through high-level outlets is known by Stack ventilation or convective air movement by drawing in lower level cool night air or cooler daytime air from sheltered external areas (south) or evaporative cooling millponds and fountains.
Figure 2.3 Convection causes warm air to rise, drawing in cool air.
If the Convective of air movement progresses cross-ventilation and overcomes several of the limits of defective cooling breezes. Even when there is no breeze, convection allows heat to leave a building through clerestory windows, roof ventilators and vented ridges, eaves, gables and ceilings.
Convection produces air movement accomplished of cooling a building but regularly has unsatisfactory airspeed to cool persons.
2.7.2 Solar chimney
The Solar chimneys improve stack ventilation by providing extra height and well-designed air passages that growth the air pressure difference. Warmed by solar radiation, chimneys heat the growing air and increase the difference in temperature between incoming and out-flowing air.
The increase in natural convection from these measures improves the draw of air through the building.
Figure 2.4 Solar chimneys enhance ventilation.
Source: Green Builder Solar Guidelines (Residential)
Figure 2.5 Solar chimney ventilation
Solar chimneys are mainly real in weathers that are humid and hot. They are most effective when they are high and inclusive, but not actual deep. This maximises the surface area that can engage solar radiation and maximises the surface area in contact with the air inside the chimney.
Variations in design can incorporate multiple chambers to further increase surface area and may use materials with high solar absorption such as metal to maximise the temperatures attained within the chimney. Low-emissivity coverings and finishing can also be used to reduce heat losses back to the outside, like the design of tromba walls.
It is important that the chimney is insulated from the building itself so that heat gains do not transmit into occupied spaces. In cooler surrounding the chimney can be used to direct absorbed heat back into the building by closing it at the top.
2.8 EVAPORATION COOLING
Evaporative cooling is a process that uses the result of evaporation as a natural heat sink. The amount of sensible heat absorbed depends on the amount of water that can be evaporated Sensible heat from the air is absorbed to be used as latent heat necessary to evaporate water.
Indirect evaporative cooling, the water content of the cooling air increases because air is in contact with the evaporated water. Evaporative cooling can be direct or indirect passive or hybrid in indirect evaporative cooling, evaporation occurs inside a heat exchanger and the water content of the cooled air remains unmovable. Since high evaporation rates might increase relative humidity and create discomfort, direct evaporative cooling can be applied only in places where relative humidity is very low.
Anywhere evaporation happens obviously it is called passive evaporation. Space can be cooled by passive evaporation where there are surfaces of still or flowing water, such as basins or fountains. Where evaporation must be controlled by means of some mechanical device, the system is called a hybrid evaporative system.
Figure 2.6 Evaporative cooling with hot dry air and cool refreshing air
Eco Cooling CREC systems can be reduce cooling costs by, comply with ASHRAE. Our evaporative cooling and ventilation systems are designed to be used. Evaporative Cooling is the least expensive air conditioning system available for cooling your home.
Figure 2.7 Direct and indirect cooling
Source: http://tkaltec.ru/evaporative-cooling-system
Indirect evaporative cooling sensibly cools the air with. Celsius are market leaders in the supply and installation of evaporative cooling systems to factories, shops, and offices. We have installed the biggest single. MECHON are the industry experts in the installation of evaporative cooling systems.
2.8.1 Passive downdraft
In this system, the tower is with moistened cellulose cloth at the top of the tower. it is evident that the total energy consumption of buildings for cooling purposes varies as a function of the quality of design and climatic conditions. The water sprayed on the pad gets composed and re-circulated by a pump. Therefore, sustainable architecture can have a large impact on environmental sustainability. It is a method where building knowledge is combined with the concept design to reduce the need for high-tech systems and the energy consumption of buildings.
Figure 2.8 Passive downdraft ventilation in building
Source: https://www.buildotechindia.com/cooling-needs-sustainability/.
2.8.2 Roof surface
The heat on roof surface can be reduced by spraying water on water retaining material and rooftop vegetation. Solar radiation incident on the roof results in overheating of rooms below them.
Figure 2.9 Combined radiative and evaporative cooling can be integrated together to increase the rate of cooling
2.9 EARTH COUPLING
Earth coupling of thermal mass protected from external temperature extremes (e.g. floor slabs) can substantially lower temperatures by absorbing heat as it enters the building or as it is produced by household activities.
Figure 2.10 Earth coupling utilizes cooler ground temperatures.
Poorly shaded surrounds can lead to earth temperatures beyond internal comfort levels in many areas. In this event, an earth-coupled slab can become an energy liability. Passively cool areas everywhere earth-coupled slabs keep surface ground temperatures lower during the day and allow night-time cooling.
Ground and soil temperatures vary from places. Earth-coupled construction (including slab-on-ground and earth covered or beamed) utilizes stable ground temperatures at lower depths to absorb household heat improvements.
2.9.1 Direct coupling
Direct coupling or earth take shelter occurs when a building uses earth as a barrier for the walls. Earth sheltering improves the presentation of building coverings by reducing heat losses and reduces heat gains by limiting infiltration. The earth acts as a heat sink and can effectively mitigate temperature extremes.
2.9.2 Indirect coupling
Indirect coupling refers to the building is joined with the earth by means of earth ducts. An earth duct is a forgotten tube that acts as a venue for source air to travel finished before entering the building. Earth ducts classically involve long tubes to cool the supply air to a suitable temperature before entering the building. It should be a fan is required to draw the air from the earth duct into the building. The supply air is cooled by conductive heat transfer between the tubes and nearby soil. Therefore, earth ducts will not perform well as a source of cooling unless the soil temperature is lower than the desired room air temperature. Some of the factors that affect the presentation of an earth duct are duct length, number of curves, the thickness of pipe wall, depth of duct, the width of the duct, and airspeed.
2.10 PASSIVE COOLING DESIGN PRINCIPLES
The building covers are designed to minimise daytime heat gain, maximise night-time heat loss, and encourage cool breeze access when offered to achieve thermal comfort in cooling needs. Considerations include:
‘ Designing the floor plan and construction form to rejoin to local weather and location
‘ Connecting and acceptably putting suitable groupings of both reflective and bulk insulation
‘ using and standing thermal mass sensibly to store chilliness, not unwanted heat
‘ choosing climate suitable windows and glazing
‘ placing windows and openings to improve air movement and cross ventilation
‘ shading windows, solar exposed walls, and roofs anywhere imaginable
‘ By providing of roof spaces and outdoor living areas as bumper zones to bound heat increase.
”Energy score software, such as that credited under the Countrywide House Energy Rating Scheme (NatHERS), can pretend their communication in any design for 69 different Australian climate zones. Integration of these variables in climate-appropriate proportions is a complex task. While the NatHERS software tools are most commonly used to rate energy efficiency (thermal performance) when assessing a house design for council approval, their capacity, in ‘non-rating mode’, as a design tool is currently under-used. Seek advice from an accredited assessor (Association of Building Sustainability Assessors or Building Designers Association of Victoria) who is skilled in using these tools”
2.11 ENVELOPE DESIGN
Envelope design is the combined design of building form and materials as a total structure to realize optimal comfort and energy savings.
A Good design of the envelope and interior layout replies to climate and site environments to optimise the thermal performance. It can lower operational costs, improve comfort and lifestyle and minimise eco-friendly impression.
Heat arrives and greeneries a home over the roof, walls, windows, and floor, together referred to as the building envelope. The internal layout walls, doors, and room measures also affect heat circulation inside a house.
All hot climates currently necessitate some grade of passive cooling with climate change this is likely to rise.
Diverse replies are compulsory for each climate zone and even within each zone dependent on resident conditions and the microclimate of a given place.
‘ Maximise the indoor’outdoor connection and provide outdoor living spaces that are screened, shaded and rain protected.
‘ Maximise convective ventilation with high equal windows and ceiling or roof space vents.
‘ Zone living and sleeping areas properly for climate ‘ vertically and flat.
‘ Locate bedrooms for sleeping comfort.
‘ Design ceilings and position furniture for the optimum competence of fans, cool breezes, and convective ventilation.
‘ Locate automatically cooled rooms in thermally protected areas (i.e. highly insulated, shaded and well-sealed).
2.12 THERMAL MASS
Thermal mass is the storage system for warmth and ‘coolth’ (the absence of warmth) in passive design. Weather responsive design means positioning thermal mass where it is exposed to appropriate levels of passive summer cooling (and solar heating in winter). Seriously located mass heats up and radiates heat well into the night when external temperatures have dropped.
As a rule of thumb, avoid or limit thermal mass in upstairs sleeping areas. In climates with little or no heating requirement, low mass is commonly the favored decision Thermal mass.
Earth-coupled material slabs-on-ground afford a heat sink where deep earth temperatures (at 3m depth or more) are favorable, but should be avoided in climates where deep earth temperatures contribute to heat gain. In these regions, use open vented floors with high levels of insulation to avoid heat gain.
Figure 2.11 In areas, wherever deep earth temperatures are lower, consider enfolding subfloor parts to permit earth coupling to lessen temperatures and so heat increases.
2.13 SHADING
Direct sun can produce the similar heat as a single bar heater over each square meter of a surface, but effective covering can block up to 90% of this heat. A variety of protecting techniques can help, from fixed or changeable shades to trees and undergrowth, depending on the building’s location as well as climate and latitude.
By shading a construction and its outdoor spaces we can reduce summer temperatures, advanced luxury and save energy.
Shading cut-glass is the greatest way to reduce undesirable heat gain, as the insecure glass is often the highest source of heat inflowing a home. However, fixed shading that is unfortunately designed can block winter sun, while general summer shading can reduce incoming daylight, increasing the use of artificial lighting. Shading uninsulated and dark colored walls can also lessen the heat weight on a structure.
Healthy heat from the sun permits finished glass and absorbed by building essentials and fixtures, which then re-radiate it inside the house. Re-radiated heat has a lengthier wavelength and cannot pass back out finished the glass as easily. In most weathers, ‘trapping’ healthy heat is wanted for winter space heating but must be avoided in summer.
Protecting of wall and roof exteriors is therefore important to lessen summer heat gain, predominantly if they are dark colored or heavyweight. Light colored roofs can reproduce up to 70% of summer heat increase.
Figure 2.12 Solar radiation is re-radiated inside
Shading requirements vary according to climate and house orientation, as shown below.
Orientation Suggested shading type
North Fixed or adjustable horizontal shading above window and extending past it each
side
East and west Fixed or adjustable vertical louvers or blades; deep verandas or pergolas with
deciduous vines
NE and NW Adjustable shading or pergolas with deciduous vines to allow solar heating or
verandas to exclude it
SE and SW Planting: deciduous in cool climates, evergreen in hot climates
2.13.1 Fixed shading
Fixed shading devices like eaves, awnings, pergolas, and louvers can control solar entree on northerly raises through the year, deprived of demanding any user effort.
Summer sun after the north is at a high position and is easily excluded by fixed horizontal plans over openings. Winter sun from the north is at a lower angle and enters beneath these devices if properly considered.
2.13.2 Adjustable shading
Adjustable shading permits to the user to select the favorite level of shadow. This is mainly useful in spring and autumn when heating and cooling needs are adjustable Active systems require active users.
Climate change does not affect sun angles, but also the attraction of shade or solar heat gain might change, thus moving the overall design plan. Adjustable shading mechanical or seasonal vegetation facilitates adaptation to changing climatic environments.
‘ Using plants for shading
Match plant features such as vegetation density, covering height and spread to shading necessities. Choose local native species with low water necessities wherever likely.
Figure 2.13 Plants can provide shade and act as windbreaks.
In addition to providing shade, plants can contribution cooling by transpiration. Plants also improve the visual environment and create agreeable filtered light see Landscaping and garden design.
‘ Deciduous plants allow winter sun to complete their bare brushwood and ignore summer sun with their leaves.
‘ Trees with tall coverings are useful for shading rooftops and large portions of the building structure.
‘ Shrubs are suitable for more localized shading of windows.
‘ Wallcreepers and ground cover cloister against summer heat and reduce reflected radiation.
‘ Shading for a healthier environment.
Apposite shading performs to reduce the chance of exposure to harmful ultraviolet rays. Implanting is a low cost, low energy provider of shade that recovers air eminence by cleaning pollutants.
2.14 AIR MOVEMENT AND VENTILATION
Design to maximise helpful cooling breezes by providing multiple flow paths and minimising possible barriers, single depth rooms are ideal for warmer climates.
Since breezes come from many instructions and can be bounced or unfocused, location to breeze course is less important than the actual design of windows and openings to collect and direct breezes within and finished the home.
Using of window windows to catch and deflect breezes from variable positions.
Figure 2.14 Types of windows
Source: Dep’t of Environment and Resource Management
For breeze, gathering window design is more important than location.
It does not blow through the building it is lapped near areas of lesser air pressure. Openings near the center of the high-pressure zone are more actual because the pressure is highest near the center of the windward wall and diminishes toward the edges as the wind finds other ways to move around the building. To draw the breeze finished use of larger openings on the leeward low pressure or downwind side of the house and smaller openings on the breeze or windward high pressure or upwind side.
Figure 2.15 Airflow pattern and speed for different opening areas.
In climates, demanding wintertime heating is need be for passive solar north sun effects these considerations designers should endeavor for a balanced approach.
The design of beginnings to direct airflow inside the home base is a serious but much-overlooked design component of passive cooling. Size, type, external shading and horizontal/vertical position of any openings doors and windows is critical as shown in the diagrams below.
Figure 2.16 Airflow through louvers
Source: Steve Szokolay
The Airflow design for windows of changed opening height. Louvre windows help to vary ventilation pathways and control airspeed.
In climates requiring cooling only, consider placing similar panels above head height in internal walls to allow cross-ventilation to move the hottest air. Consider fitting a louver window overhead door to let breezes pass finished the building though preserving privacy and security. Position windows vertically and horizontally to direct airflow to the area where occupants spend the most time (e.g. dining table, lounge or bed).
CHAPTER 3 ‘ CASE STUDY
3.1 CASE STUDY -1
INTRODUCTION
‘ PEARL ACADEMY OF FASHION, JAIPUR
‘ India
‘ Educational Building
‘ College
The Pearl Academy of Fashion is in a typical hot, dry, desert type climate on the environs of Jaipur in the bleak Kakas industrial area around 20 kilometers from the famous enclosed city. The Pearl Academy ranks third in the top 10 fashion design institutes in India. Its design represents the significance of its academic orientation. Architecture in Jaipur currently is a kitschy rendition of Rajasthani classicism and Mughal architecture remnants.
The architecture of the academy desired to be a union of modern adaptations of traditional Indo-Islamic architectural elements and passive cooling plans prevalent in the hot-dry desert climate of Rajasthan such as open courtyards, water body, a step-well or boil and perforated stone or latticed screen. All these elements have been derived from their historic traditions, but will manifest themselves through the built form and become an essential part of the daily life of the designers.
The only way by which these designs could be achieved was to practically eliminate HVAC by installing passive and low energy strategies among other cost-saving strategies such as the use of local materials, techniques etc.
PLAN OF BUILDING
3.2 LITERATURE CASE STUDY -2
The Walls and Vaults House in India is a green home for a family with two kids and their grandparents. Tucked into a moderate slope in a small town in Kottayam district, the house comprises several curved volumes, with stone walls wrapping around the structure and enclosing lush tropical vegetation as part of the house. Architecture studio LIJO.RENY. designed the residence to withstand heavy monsoons and scorching sun.
The house is hidden from three sides, only one side is visible from the road. Its materiality and colors were chosen carefully to balance the surroundings and blur the line between inside and outside. Lush vegetation fills the interior with a large stone wall and creates a passage that runs the entire length of the house. Two enclosed landscaped areas emphasize the natural environs.
Maximum of the externally visible walls are built from locally obtained granite using traditional building techniques. These structures also act as thermal barriers that help to keep the house cool during hot summer and providing best levels of privacy for the residents.
PLAN OF THE HOUSE
The Walls and Vaults House in India is a green home for a family with two kids and their grandparents. Tucked into a moderate slope in a small town in Kottayam district, the house comprises several curved volumes, with stone walls wrapping around the structure and enclosing lush tropical vegetation as part of the house. Architecture studio LIJO.RENY. designed the residence to withstand heavy monsoons and scorching sun.
The house is hidden from three sides, only one side is visible from the road. Its materiality and colors were chosen carefully to blend into the surroundings and blur the line between inside and outside.
Lush vegetation fills the interior with a large stone wall and creates a passage that runs the entire length of the house. Two enclosed landscaped areas emphasize the natural environs.
INTERIORS
Source: http://inhabitat.com/wp-content/blogs.dir/1/files/2016/01/The-Walls-and-Vaults-House-by-LIJO.RENY_.architects-23-1020×61
CHAPTER 4 ‘ MATERIALS AND DESIGNING
4.1 MATERIALS AND METHODS OF CONSTRUCTION
Around of the materials and methods used to design suitable natural ventilation systems in buildings are solar chimneys, wind towers, and summer ventilation control methods. The chimney is isolated from the occupied space and can be heated as much as possible by the sun or other means. Air is exhausted out from the top of the chimney and creating suction at the bottom which is used to extract musty air.
A solar chimney may be a real answer wherever usual breezes are not dependable sufficient to depend on wind-induced ventilation and where keeping indoor temperature satisfactorily above the outdoor temperature to drive buoyant flow would be unacceptably warm.
Wind towers outdid with fabric sails that guides wind into the building is a common feature in historic Arabic architecture and are known as ‘mosque's’. The received air is often absorbed as a fountain to achieve evaporative cooling and good ventilation. At night, the process is reversed and the wind tower acts as a chimney to vent room air. A modern difference called a "Cool Tower" puts evaporative cooling essentials at the top of the tower to force to supply cool and dense air.
During summer once the external temperature is below the wanted inside temperature, windows should be opened to maximize fresh air intake. Airflow is needed to preserve the inside temperature not more than 3-5 ”F above the outside temperature. During hot and calm days, air exchange rates will be very low and the tendency for inside temperatures is to rise above the outside temperature. The use of fan-forced ventilation or thermal mass for healthy cooling may be important in controlling these extreme temperatures.
4.2 DESIGN CONSIDERATION
The specific approach and proposal of natural ventilation organizations will vary constructed on building nature and with the weather. However, the volume of ventilation depends upon the design of interior spaces, the size, and location of openings in the building.
‘ To Maximize wind-induced ventilation by placement the elevation of a building perpendicular to the summer breezes.
‘ Estimated wind guidelines are potted in seasonal "breeze design" plans obtainable in the Nationwide Oceanographic and Atmospheric Administration (NOAA). However, these designs stay frequently built on information occupied at airfields. Real ethics at a remote building location can change intensely.
‘ Buildings should be placed where summer breeze obstructions are minimal. A windbreak of evergreen trees may also be useful to lessen cold winter winds that tend to come frequently from the north.
‘ Naturally ventilated buildings should be narrow.
It is very tough to distribute fresh air to all portions of a wide building area using natural ventilation. The maximum width that one could expect to ventilate naturally is assessed at 45 ft. Consequently, buildings that depend on natural ventilation often have an articulated floor plan.
Each room should have two separate and exhaust openings. Locate exhaust inlet to maximize stack effect. Orient windows across the room and offset from each other to maximize mixing within the room while minimizing the obstructions to airflow within the room.
Window openings should be operable by the occupants.
‘ Provide ridge vents.
An edge vent is an opening at the peak point in the rooftop that affords a good outlet for both confidence and wind-induced ventilation. The edge opening should be free from barriers to allow air to easily flow available of the construction.
‘ Allow for adequate internal airflow.
In totaling to the main consideration of airflow in and out of the building, airflow among the rooms of the building is important. When probable, interior doors should be designed as openable to encourage whole-building ventilation. If confidentiality is required, ventilation can be provided finished high louvers or windowpanes.
‘ Consider the use of clerestories or vented skylights.
A clerestory or a vented skylight will provide an initial for stale air to seepage in a buoyancy ventilation plan. The light of the skylight might also act as a solar chimney to increase the flow. Beginnings lower in the structure, such as basement windows must be provided to whole the ventilation system.
‘ Provide attic ventilation.
In buildings with lofts, ventilating the attic space importantly decreases heat transmission to conditioned rooms below. Ventilated lofts are about 30”F cooler than airless lofts.
‘ Consider the use of fan-assisted cooling strategies.
Ceiling and whole-building fans can offer up to 9”F effective temperature drop at one-tenth the electrical energy consumption of mechanical air-conditioning structures.
‘ Determine if the building will benefit from an open- or closed-building ventilation approach.
A closed-building method works well in hot, dry climates wherever here is a large variation in temperature from day to night. A massive building is ventilated at night, then, closed in the morning to keep out the hot daytime air. Residents are then cooled by radiant exchange with the massive walls and floor.
An open-building approach works well in warm and humid areas, where the temperature does not change much from day to night. In this case, daylight cross-ventilation is encouraged to maintain indoor to outdoor temperatures.
‘ Use automatic cooling in hot, humid weather.
‘ Try to allow natural ventilation to cool the mass of the building at nightly in hot weathers.
‘ Open stairways provide stack effect ventilation then observe all fire and smoke protection for enclosed stairways.
CONCLUSION
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