Sunday, 29 April 2012

Climate Related Building Design


Following climate factors are important for climate-related building:
  • solar radiation (direct and diffuse)
  • temperature and fluctuation in temperature (seasons, day/night)
  • air humidity
  • air movements (main wind direction, storm force)
  • precipitation (quantity and seasonal fluctuation)
The basis for climate-related building is the combination of strategies of traditional architecture and modern development. For strategies and concepts of traditional architecture of the different climate zones.
Traditional building concepts cannot be completely adopted to the architecture of the metroplitan areas of our complex industrial society. But traditional architecture demonstrates the various possibilities influencing the indoor climate by structural measures without additional appliances and with a mimimum of energy.
 The following table provides a reference guides to the main climatic zones as well as the key design responses for each climate:

polar/subpolar climate
temperate climate
dry climate
subtropical climate
tropical climate
thermal mass
massive
depending on region
low *
thermal insulation
necessary
necessary
only in case of artificial cooling
depending on region
only roofs and air-conditioned buildings
heat storage
heat protection
in summer
balance of alternation of day and night
normally not necessary
unwanted
heating
necessary
notwendig
regional in winter
regional in winter
not necessary
active cooling
not necessary
in the majority of cases avoidable
often necessary
often necessary
seasonal necessary
ventilation
controlled
controlled
controlled or increased
increased ventilation*
increased ventilation all the the year*
(cross ventilation)
air tightness
necessary
necessary
only in case of artificial cooling
necessary
only in case of artificial cooling
shading (without visors)
seldom necessary
temporary in summer
necessary
necessary
necessary
*only in case of no artificial cooling


1.    Polar and Subpolar Climate
 The buildings of this climatic zone serve as protection against cold in the first instance. Effective heating systems are very important. These heating systems require energy, but passive design features given below help to reduce the energy required. Multi-layered wall and roof structures or massive constructions are considered to be climate- related building envelopes. Building elements exposed to weather shall consist of weatherproof materials.
basic constructional requirements:
  • protection against cold (heat insulation)
  • protection against storms
  • protection against humidity, especially around roof areas
  • if possible use solar energy in summer
Building Location, Building Surroundings
The temperatures of building's surrounding influence the annual amount of energy necessary to heat the building.
  • wind-protected locations reduce heat loss
  • usage of vegetation and topography as natural windbreak   
Building Shape
  • optimised A/V-ratio for reduction of heat transfer by building envelope
  • roof overhangs and steep roof pitches (especially on north facades) shed rain and snow away from the house and prevent premature deterioration of exterior finish materials (northern hemisphere)
 Building Orientation
Depending on the main wind direction, the main facade should be oriented to the south (northern hemisphere) or to south on the southern hemisphere in order to achieve maximum solar gains.
  • sun-exposed facades with short roof overhang on the south-facing facade (northern hemisphere)
  • south-facing building openings (northern hemisphere) with insulated shutters or roller shutters
  • protection against north and north-west
Zoning of Buildings
Zoning implies the location of rooms with higher heating needs such as living areas on the south side, while the north side accommodates function and utility rooms. Garages and secondary rooms oriented to the north act as thermal buffer zones. Attics, basement rooms and entrance porches are thermal buffer zones between inside and outside as well.
  • include thermal buffer zones
  • porched entrances areas
  • living areas are located in the south, whereas function and utility rooms are located in the north
Walls and Roof
  • multi-layered wall and roof structures or massive constructions with low U-value
  • include snow loads
  • vapour barrier should be placed on the inside
  • choose jointless and airtight constructions
  • protect building elements against humidity, especially in roof areas
  • use double or if necessary triple glazing
Windows
  • insulated glazing with low proportion of frame and appropriate U-values (quality of glazing, proportion of frame, edge seal)
  • glazing with appropriate g-value (SHGC) for solar gains
  • appropriate apertures (large south-facing windows, small north-facing windows)
  • insulated shutters or roller shutters
2.    Temperate Climate
Moderate climates are determined by distinctive seasonal fluctuations with strong temperature variations between summer and winter. The climatic conditions vary from region to region. Decisive factors are continentality, maritime impacts, latitude and elevation above sea level. The most buildings of this climatic zone have to meet the following basic requirements:
  • protection against cold in winter (heat insulation)
  • protection against overheating in summer
  • protection against precipitation
  • if possible use solar energy in summer
Building Location, Building Surroundings
The temperatures of building's surrounding influence the annual amount of energy necessary to heat the building.
  • wind-protected south slopes reduce heat losses
  • fresh air corridors provide ventilation and improve urban thermal environment, broad streets and open building development contribute to better ventilation
  • usage of vegetation as natural windbreak or wind-guiding element
  • vegetation around the building improves the microclimate (humidity, temperature, dust, air pollutants)
Building Shape
Temperature compensation between building and its surroundings is influenced by building shape and building orientation.
  • choose a compact shape
 Building Orientation
  • orientation of the building subject to solar access
  • south-facing main facade and south-facing apertures for maximum solar gains (northern hemisphere)
  • protection against north and north-west (northern hemisphere)
  • include the possibility of cross ventilation in summer
 Zoning of Buildings
The rooms are classified according to their function and time of usage. Zoning implies the location of rooms with higher heating needs on the sunny side, while the shady side accommodates function rooms.
  • function rooms are located in the north, whereas the living area is located in the south
  • rooms of low temperatures act a thermal buffer between inside and outside
  • include entrance porches (as thermal buffer zones)
Walls and Roof
  • multi-layered wall and roof structures or massive constructions with low U-value
  • vapour barrier should be placed on the inside
  • choose jointless and airtight constructions
  • choose shape of roof, roof overhangs and roof drainage according local conditions (amounts of precipitation and snow loads)
  • use insulated glazing
Windows
  • insulated glazing with low proportion of frame and appropriate U-values (quality of glazing, proportion of frame, edge seal)
  • glazing with appropriate g-value (SHGC) for solar gains
  • appropriate apertures (large south-facing windows, small north-facing windows)
  • orientation of windows and position of the window in connection with interior spaces for good daylighting: clerestories, skylights and high windows improve the brightness of a room; windows in the centre of the wall distribute the light better in the depth of the room than corner windows
  • insulated shutters or roller shutters only if necessary
Shading
During the hot season, shading devices are very important: Shading devices have to be chosen according to window orientation:
  • protection against noon sun angle : horizontal shading (for south facades, northern hemisphere)
  • protection against low hanging sun : vertical louvers or fins (for east and especially west facades)
  • For maximum solar gains, it is a wise idea to choose adjustable shading devices wherever possible
 3.   Subtropical Climate
Subtropical climate zones are determined by distinctive seasonal fluctuations with temperature variations and different amounts of precipitation in summer and winter.
basic constructional requirements:
  • protection against overheating in summer
  • using of natural air flow for cooling in summer
  • protection against precipitations
  • shading of exterior spaces (plantings)
  • protection against winterly cold (depending on the region)
Building Location, Building Surroundings
The temperatures of building's surrounding influence the annual amount of energy necessary to heat or cool the building.
  • wind-exposed locations for effective ventilation in summer
  • fresh air corridors provide ventilation and improve urban thermal environment, broad streets and open building development contribute to better ventilation
  • usage of vegetation as natural windbreak or wind-guiding element
  • vegetation around the building improves the microclimate (humidity, temperature, dust, air pollutants)
  • planting provides shade; shade structures to lower ground temperatures
  • include evaporative cooling of water bidies and water features
  • provide appropriate screened, shaded, rain protected outdoor living spaces
 Building Shape
Temperature compensation between building and its surroundings is influenced by building shape and building orientation.
  • choose a compact shape
 Building Orientation
orientation of the building subject to solar access:
  • minimise openings in sun-exposed facades (east and west facades)
  • maximise convective ventilation with high level windows and cross ventilation (cross ventilation depends on building depth)
  • shade sun-exposed facades in summer, but passive solar heating is required during winter months
  • orient building openings to the main wind direction in summer
  • coastal areas: use cooling breezes from the sea
 Zoning of Buildings
The main element is floor plan zoning to maximise comfort for daytime activities and sleeping comfort:
  • function rooms are located in the north, whereas the living area is located in the south
  • locate bedrooms for sleeping comfort to the east
  • design unobstructed cross ventilation paths
  • locate mechanically cooled rooms in thermally protected areas (coolest zone in the house)
 Exterior Building Elements
Similar to the architecture of dry climates, it is good to use multi-layered wall and roof structures. The exterior layer protects against solar radiation, which reduces heat absorption of building elements. The interior layer minimises and retards thermal transfer to the building's interior. This effect is called phase shift (siehe Glossar) and amplitude attenuation (siehe Glossar). The thermal insulation protects against heat in summer and prevents heat loss in winter.
Walls and Roof
  • multi-layered wall and roof structures
  • vapour barrier should be placed on the inside or outside (In areas where you heat more than air condition, do place the vapour barrier on the inside whereas in areas where you air condition more than heat place the vapour barrier on the outside)
  • bright reflective facades to reduce heat gain
  • choose jointless and airtight constructions
  • choose shape of roof, roof overhangs and roof drainage according local conditions (amounts of precipitation and solar radiation)
  • shade building elements exposed to sun in summer
  • thermal insulation to prevent transmission heat loss in winter
Windows
  • shade all openings in summer and east and west openings year round
  • glazing with appropriate g-value (SHGC)
  • glazing with appropriate U-value
  • adequate window areas
  • orientation of windows and position of the window in connection with interior spaces for good daylighting: clerestories, skylights and high windows improve the brightness of a room; windows in the centre of the wall distribute the light better in the depth of the room than corner windows
Shading
Shading devices are very important all the year round. Include planting design to shade the building. Shading devices have to be chosen according to window orientation:
  • protection against noon sun angle : horizontal shading (for south facades, northern hemisphere)
  • protection against low hanging sun : vertical louvres or fins (for east and especially west facades)
  • there are combinations of vertical and horizontal shading
For maximum solar gains, it is a wise idea to choose adjustable shading devices wherever possible. Shade all windows in summer and east and west windows year round.

Ventilation
Natural breezes are an essential element of passive cooling. For this reason, it is important to include the flow of cooling breezes through a building. Generally, cross ventilation is most effective for air exchange in summer. Cross ventilation depends on the building depth. Hence, design floor plans which do not block cooling breezes.
If possible, use coastal breezes for cooling. Openings oriented to the sea improve the indoor climate.
Include convective air movement. Convective air movement relies on hot air rising at the highest point, drawing in cool air from shaded external areas. Higher room heights increase the effect.
·         cross ventilation
·         include ceiling fans to create air movement during still periods if necessary

 4.   Dry Climates
 Dry climates are determined by high temperatures all the year round. Temperature maximum is in summer, minimum is in winter.
basic constructional requirements:
  • protection against heat absorption and overheating
  • protection against direct solar radiation (humans and buildings), shades
  • usage of solar energy
  • heat storage by massive walls in day and night cycle
  • optimised A/V-balance small facade areas exposed to sun
  • usage of water and vegetation areas in order to improve the microclimate
  • shading of exterior spaces (plantings)
 Building Location, Building Surroundings
The temperatures of building's surrounding influence the annual amount of energy necessary to cool the building.
  • narrow streets and alleys protect against hot winds
  • build the streets narrow so the buildings shade each other during the day
  • use vegetation, walls and banks as natural windbreak
  • vegetation around the building improves the microclimate (humidity, temperature, dust, air pollutants)
  • include water bodies for evaporative cooling
Building Shape
Temperature compensation between building and its surroundings is influenced by building shape and building orientation.
  • compact building shape, closed structure with small exterior areas
  • include atria and outdoor courtyards for (evaporative) cooling
 Building Orientation
Orient the building with the short wall facing west or southwest for the least solar gain in the summer.
  • minimise exterior areas exposed to the sun
  • minimise windows on east and west facades
  • shade building elements exposed to sun (roof, east and west facades)
  • shade building openings
Zoning of Buildings
Floor plan zoning is very important. Locate bedrooms for sleeping comfort on the east side of the building: east-oriented rooms are only exposed to direct sun in the morning, so there is enough time to release the absorbed heat until dusk.
  • locate bedrooms for sleeping comfort to the east
  • provide multiple flow paths and minimise potential barriers
Exterior Building Elements
Multi-layered wall and roof structures help to reduce the wall thickness of massive traditional architecture of hot climates. The exterior layer protects against solar radiation, which reduces heat absorption of building elements. The interior layer minimises and retards thermal transfer to the building's interior. This effect is called phase shift (siehe Glossar) and amplitude attenuation (siehe Glossar) and it is made possible by thermal inertia of traditional massive wall structures or by insulation materials.
Walls and Roof
  • multi-layered wall and roof structures or massive structures of high thermal mass
  • double skin roof with a light outer layer with reflective surface
  • vapour barrier should be placed on the outside in case of mechanical cooling
  • bright reflective facades to reduce heat gain
  • choose jointless and airtight constructions in case of mechanical cooling
  • shade building elements exposed to sun (planting, roof overhang...)
 Windows
  • shade all building openings
  • appropriate window areas (only small or no windows on east and west facades)
 Shading
In hot and dry climates shading devices are of special importance.
Shading devices have to be chosen according to window orientation:
  • protection against noon sun angle : horizontal shading (for south facades, northern hemisphere)
  • protection against low hanging sun : vertical louvres or fins (for east and especially west facades)
  • there are combinations of vertical and horizontal shading
Building elements and openings exposed directly to the sun should be shaded.

Ventilation
Due to high temperatures, natural breezes often cannot be used for cooling the building. Using breezes for cooling requires outdoor temperatures below 35°C. But it is possible to include convective air movements (stack effect) for cooling. Traditional devices using this effect are so called "wind catchers" (Persian: Badgir). Badgirs can be found in Persia and Egypt.




5.   Tropic Climate
 basic constructional requirements:
  • protection against heat absorption and overheating
  • protection against direct solar radiation (humans and buildings), shades
  • protection against mugginess (humidity)
  • protection against humidity penetration and driving rain
  • usage of solar energy
Building Location, Building Surroundings
The temperatures of building's surrounding influence the annual amount of energy necessary to cool the building.
  • wind-exposed locations
  • wind-guiding elements (walls, hedges, trees)
  • shading of the building
  • shading of exterior spaces (plantings)
  • vegetation around the building improves the microclimate (humidity, temperature, dust, air pollutants)
 Building Shape
Temperature compensation between building and its surroundings is influenced by building shape and building orientation.
  • stilt houses elevated above the ground allow ventilation beneath the floor
  • use single room depths where possible to enhance cross ventilation and heat removal
  • pitched roofs protect agains heavy downpours
  • roof overhangs shade the facade and protect against intense rain
  • design properly ventilated roofs
  • add open-sided storeys or stilt floors in multi-storey buildings to allow better ventilation
 Building Orientation
  • orient the building to the main wind direction, exposure to cooling breezes should be maximised
  • minimise sun-exposed facades (east and west facades)
  • shade outdoor areas such as courtyards, balconies and verandas
  • orient building openings to the main wind direction
  • openings on the opposite side of the house draw the breeze through and out (cross        ventilation)
  • shade all building openings
 Zoning of Buildings
The main element is floor plan zoning to maximise comfort for daytime activities and sleeping comfort:
  • locate bedrooms in cool areas of the building
  • design a layout that allows cool breezes to pass right through the house
Exterior Building Elements
The use of high mass construction is generally not recommended in hot humid climates due to their limited diurnal range. Passive cooling is generally more effective in low mass buildings, because lightweight construction responds more quickly to cooling breezes.
Insulated roofs might be advantageous. Insulated walls are only necessary in case of artificial cooling. Otherwise, heat accumulation might be the result.
Walls and Roof
  • use low thermal mass constructions
  • multi-layered, well ventilated roof structures for quick heat removal
  • ventilated wall structures
  • enhanced ventilation of roof space
  • insulate roof structures in case of mechanical cooling or in case of sun-exposed roofs
  • avoid fixed glazing
  • design light coloured external surfaces
  • controlled rain water run-off
  • protect the structure against humidity penetration
  • include appropriate shading devices
Tropical cyclones are an accepted part of life in some tropical areas. These thunderstorms or cyclones cause pressure on surfaces of buildings, which leads to loads on the structure. Hence, there are structural materials standards to select elements that can resist the required wind actions. A large number of structural elements must be functioning correctly to avoid wind damage caused by pressure and suction. Tropical thunderstorms often come along with heavy downpours. So there might be a need for circumferential drainage in order to protect the building against undercutting.
 Windows
  • shade all building openings
  • appropriate window openings (according to orientation: small apertures in east and        west facades)
  • no fixed glazing, use windows equipped with flexible louvres
 ShadingIn tropic climates shading devices are of special importance.
Shading devices have to be chosen according to window orientation::
  • protection against noon sun angle : horizontal shading (for south facades, northern hemisphere)
  • protection against low hanging sun : vertical louvres or fins (for east and especially west facades)
  • there are combinations of vertical and horizontal shading
  • sun shade devices must not reduce the air flow considerably
  • include natural vegetation for shading (plants contribute to cooling by evaporation)
Shade sun-exposed external surfaces and all building openings. Choose endemic plants for shading. Plants create pleasant filtered light and assist cooling by evaporation.
Ventilation
High temperatures and high humidity require maximum ventilation to reduce heat and humidity loads. Natural air flow may contribute to cooling:
  • openings on the opposite side of the house allow cross ventilation
  • ventilated roof spaces for heat removal
  • stilt structures and open-sided storeys allow better ventilation
  • use convective air movements (stack effect)
  • include ceiling fans to create air movement during still periods if necessary (e.g. at night)

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