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The building and construction sector is a key sector for sustainable development. The construction, use and demolition of buildings generate substantial social and economic benefits to society. Construction technologies have improved the buildings we work or live in and provide benefits for the environment and the building owners. Rather than constructing buildings for particular climates, technology has lead us in the way of producing energy efficient buildings and providing passive designs for sustainable houses. This enables us to manipulate the climate we live in and use these methods to benefit or buildings or homes regards to the environment. Given that an average house lasts for more than 60 years, providing passive design principles for builders or renovators, the integration of passive design is a wise investment choice as part of future-proofing your home and making it perform more sustainably as it can effectively respond to a site's prevailing climatic conditions. The report discusses the passive design principles and associated information that can improve household comfort, liveability and savings in each of the different climate zones. It presents a summary of passive design concepts and benefits that can be used to assist in designing a new house, or altering or purchasing an existing house.
2.0 FUNDAMENTAL PASSIVE DESIGN PRINCIPLES
Passive design is a key feature of a sustainable house. There are six design principles that are employed in the design to achieve sustainability these are discussed in order of priority; 'orientation, ventilation, shading, insulation, thermal mass and materials' (J.W. 1975).
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House orientation is the most fundamental passive design principle as it significantly affects the house's comfort and energy performance. Consider how the plan interacts with the site, as good orientation increases the benefits of solar access, cooling breezes, summer shading and wind protection. (J.W. 1975)
If possible, its recommended houses are to be orientated so their western side blocks out the heat from the low summer sun, and their south-western side acts as a buffer against westerly winds.' As a general rule, window area on the north-facing wall should be 10-25 percent of the floor area of the room so that the room can gain suitable access to winter sun'. (J.W. 1975)
The southern side of the houses should normally be shaded, as this can provide some liveable outdoor space in summer. However it should also be recognised that this space can occasionally get cool on winter days, so design this space for flexible use. In Tropical climatic zones, the midday summer sun strikes the southern face of the house, while midday winter sun is toward the north.
Throughout Australia's summer, the ultimate home comfort aim is to live in a house so well ventilated and shaded that it would be like sitting under a large tree on a hot day where the breeze can pass unhindered. Such a concept can be incorporated into a house through applying the design features presented below:
As windows and door openings receive breezes, 'the more flexible the opening the better its potential for ventilation' (J.W. 1975). Louvers and awning windows can direct the breeze down into the living space of a room. They need not all be glass, as timber louvers provide shade as well as breeze (preferred to chose from plantation timbers).
Once the breeze is inside the house it should be able to flow through to the other side as uninterrupted as possible. Careful planning of rooms is required such as (wherever possible) two windows in each bedroom to provide better cross ventilation. Attempt to locate doors adjacent to each other as this can also assist with cross ventilation. 'As air moves upward when heated, adjustable fanlights or vents are recommended over internal door openings to remove the hot air accumulating at ceiling level in summer' (Milne Geoff.2005). They also need to be able to be closed to reduce heat loss in winter. Vents located in flat ceilings in the hallway and kitchen can provide an additional advantage, as long as the roof is adequately ventilated. This allows the heat gathered at ceiling level to be expelled up into the roof space. Ceiling vents in Sub-tropical climates also need to be sealed in winter to keep the warmth in. (Claudia. 2004)
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Roof space and colour
Effective roof ventilation can remove this heat build up through openings in the roof's eaves and the placement of ridge vents. 'The ridge can be vented in a number of ways. The first is a short gable at the ridge providing required weathering protection and permanent ventilation. The clerestory design also offers an alternative for ridge venting'. (Milne Geoff.2005). The openable venting area can be greatly increased, though the opening should not be located towards the summer sun as that could allow unwanted solar gain. A solution to this problem when using metal deck roofing is to simply provide a second skin of sheeting at the ridge, close enough to the main roof to prevent rain entering yet sufficient to allow heated air inside to escape.
A light-coloured roof is also a good advantage. As a bitumen road readily absorbs heat because of its colour, a dark roof does the same. A light-coloured roof can reflect unwanted heat before it even gets into the roof space. Whilst it is incorrect to suggest that all roofs should be white, those with a light-coloured roof will reduce the heating capacity of their home's roof space, and thereby potentially enhancing comfort levels and minimising energy demands.
Cathedral ceilings are angled, with ceiling sheets fixed to the underside of rafters or scissor trusses. They are ideal in hot climates if they are designed properly. Unwanted heat from the habitable areas rises away from the house as it warms the air and accumulates at the highest point of the ceiling.' If the warmed air is not allowed to escape it will eventually fill the room, so it is essential to release the heat gathered at the ridge, either into a ventilated roof space or directly outside through wall openings placed just below the highest part of the ceiling'. (Milne Geoff.2005). Cathedral ceilings often have little or no roof space that would normally assist to reduce heat flows between the roof and the ceiling, so it is also important to provide good roof and ceiling insulation.
Proper landscaping, pools or water features and other external shading devices such as verandas, overhangs, awnings and pergolas can also reduce the air temperature before it reaches the house.
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Shading includes roof eaves (overhangs), window eaves (awnings), as well as significant vegetation that may reduce direct sunlight penetration into walls. 'As most external wall systems have a low thermal resistance, shading and/or insulation is required.'(Milne Geoff.2005). Shading lowers the house's heating capacity and can minimise the need for air-conditioning.
As the seasons change, so too does the angle of the sun. In Sub-Tropical climates, the winter sun passes lower in the northern sky. 'The house has higher exposure to direct sunlight in the cooler time of the year, as the sun's rays can pass under the overhangs and/or awnings, and naturally warm the house'. (Salmon,C. 1999). By adopting this design feature, the house can achieve a better comfort level and reduce the need for mechanical heating. Effective overhangs on the north and south of the house and shielding from the rising and setting sun on the east and west will provide adequate shading to the house for most of the year.
Window awnings are recommended where there are little or no roof eaves. However, it is not sufficient to simply attach an awning the exact width of the window as sunlight often hits the window obliquely and can heat a large proportion of the glass. 'Awnings should be wide enough to shade the window during summer when the angle of the sun is steep and hot, such as the afternoon'. (Claudia. 2004)
Houses need to be insulated from the heat in summer and, for those areas especially those in, from the cold in winter. 'Insulation can assist to reduce the effects of these extreme temperatures as it provides greater comfort levels'. (Ympäristö, 2006). As the main sources of heat flow are through glass, roofs and walls, insulation can be installed inside roofs and walls to better regulate this heat flow.
2.5 THERMAL MASS
A lot of heat energy is required to change the temperature of high density materials like concrete, bricks and tiles. They are therefore said to have high thermal mass. Lightweight materials such as timber have low thermal mass.
Appropriate use of thermal mass throughout your home can make a big difference to comfort and heating and cooling bills.
'Correct use of thermal mass moderates internal temperatures by averaging day/night (diurnal) extremes. This increases comfort and reduces energy costs'. (Ympäristö, 2006).
'Poor use of thermal mass can exacerbate the worst extremes of the climate and can be a huge energy and comfort liability'.(Claudia. 2004). It can radiate heat all night during a summer heatwave, or absorb all the heat you produce on a winter night. To be effective, 'thermal mass must be integrated with sound passive design techniques'. (Claudia. 2004). This means having appropriate areas of glazing facing appropriate directions with appropriate levels of shading, insulation and thermal mass.
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A range of energy-efficient materials can be used to assist thermal comfort and natural lighting, including:
Window size, location, glass (glazing) and frame type can significantly affect household heat loss and gain. Good window selection can optimise the combination of natural lighting, ventilation, noise control, security and visual amenity connecting interior and exterior spaces
Skylights can improve indoor lighting by allowing natural sunlight to enter the house through the roof, thereby reducing the need for artificial lighting and electricity. A skylight can be used in darker rooms and darker parts of large rooms. 'Skylights should be well sized and located so as not to allow too much bright light to penetrate through the roof' (Salmon,C. 1999), and also not to overexpose householders to direct indoor summer sun.
Solar pergolas are shade structures that have angled blades (Salmon,C. 1999), which prevent summer sun penetration (i.e. roofs that are not waterproof), but can allow the low-angled winter light and warmth to enter between the blades. Variations on the traditional solar pergola that allow the blades to be adjusted to the point of closing them completely can provide a waterproof roof. They can be an invaluable feature to a house in the sub-tropics and are ideal for the change in seasons.
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3.0 PASSIVE DESIGN BENEFITS
The incorporation of passive design elements into a new or existing house can create a more comfortable home to live in, save on its operating costs, as well as reduce its energy demand and greenhouse gas emissions. A passively designed house looks like a conventional home the only difference is it just performs better. Given that an average house lasts for more than 60 years (J.W. 1975), the integration of passive design is a wise investment choice as part of future-proofing your home and making it perform more sustainably as it can effectively respond to a site's prevailing climatic conditions.
Passive design traditionally aims to maintain a house's thermal comfort without mechanical heating or cooling by using natural energy flows - designing more with nature, not against it (Reep. Org). A house's 'building envelope', which is the roof, walls, windows and floors control the heat gain in summer and heat loss in winter. Using passive design to filter or modify a house's 'building envelope' to design for climate can significantly improve its thermal performance. A well-designed 'building envelope' will increase cooling air movement and keep out sun in the summer and in winter trap and store heat from the sun to minimise heat loss. (Claudia. 2004).
The benefits for owners of homes with passive design include lower energy costs and gaining a greater enjoyment of Australia's climate when compared with residents of conventional houses. Whilst a house that incorporates passive design features may cost slightly more upfront, it will become cost-effective over time through annual operational savings, and therefore be more affordable in the longer-term. Homeowners do not need to pay hundreds of dollars every year on heating and/or cooling costs if they take easy opportunities to access passive. Even where ideal conditions are not possible, such as being able to gain good orientation, significant levels of improved comfort and energy efficiency can still be obtained by incorporating other passive design principles.
Homeowners also have peace of mind given that their home has greater energy efficiencies, it will have a lower greenhouse gas contribution through the reduction in burning of fossil fuels for electricity generation as it performs more responsively to its prevailing climate.
4.0 OTHER FEATURES OF SUSTAINABLE HOUSING DESIGN
Sustainable technology fittings, such as solar hot water systems, rainwater tanks and solar energy supply, can significantly complement a passively designed house. All of these features are recommended to be included as part of an integrated design response as they can collectively improve the efficiencies and performance of a more sustainable house.
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A more sustainable home can incorporate a range of features to account for energy and water supply and consumption, accessibility, grey-water and black-water systems, stormwater management (minimising cut and fill on-site to maintain natural drainage patterns and detention basins), and preventing soil erosion/sediment and nutrient run-off to our waterways, and biodiversity (through maintaining significant trees) (Salmon,C. 1999).
The report reveals how fundamental passive designs provide us with techniques and methods that promote a sustainable house, revealing such things as ventilation, shading, insulation, thermal mass and materials all play a part in a sustainable home. Also highlighting the benefits of sustainable home, becoming cost-effective over time through annual operational savings, and therefore are more affordable in the longer-term. Also revealing through benefits of passive designs improved comfort and energy efficiency can be obtained by incorporating passive design principles. The report provides methods and techniques for builders and renovators on producing energy efficient and sustainable buildings. The benefits for owners of homes with passive design include lower energy costs and gaining a greater enjoyment of the climate they live in when compared with residents of conventional houses.
Passive design is a key element of sustainable building. It aims to maximise comfort for people living in a home while minimising energy use and other impacts on the environment. This means making the most of free, natural sources of energy, such as the sun and the wind, to provide heating, cooling, and ventilation to contribute to responsible energy use. These recommendations explore ideas, solutions and benefits to passive design when considering constructing in a particular climate.
Reveals house orientation is the most fundamental passive design principle as it significantly affects the house's comfort and energy performance.
Incorporating insulation designs can assist to reduce the effects of these extreme temperatures as it provides greater comfort levels
Providing appropriate use of thermal mass throughout your home can make a big difference to comfort and heating and cooling bills.
Acquiring a range of energy-efficient materials can be used to assist thermal comfort and natural lighting.
Incorporate passive design elements into a new or existing house which creates a more comfortable home to live in, save on operating costs, as well as reduce energy demand and greenhouse gas emissions.
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Passive design is design that does not require mechanical heating or cooling. Rather than constructing for a particular climate it's concerned about making the most of local conditions to make your home or construction comfortable, affordable and sustainable. The report discusses aspects of passive design. The six design principles are employed in the design to achieve sustainability these are discussed in order of priority; orientation, ventilation, shading, insulation, thermal mass and materials. In which all these aspects play a role in producing a sustainable and cost effective construction over the long run. These principles discussed reveal the benefits of passive design showing that the incorporation of passive design elements into a new or existing house can create a more comfortable home to live in, save on its operating costs, as well as reduce its energy demand and greenhouse gas emissions. The report concludes that the benefits for owners of homes with passive design include lower energy costs and gaining a greater enjoyment of the climate they live in.
The main recommendations that were explored throughout the report is it reveals house orientation is the most fundamental passive design principle as it significantly affects the comfort in a house and energy performance. Incorporating insulation designs can assist to reduce the effects of these extreme temperatures as it provides greater comfort levels. Providing appropriate use of thermal mass throughout your home can make a big difference to comfort and heating and cooling bills. Acquiring a range of energy-efficient materials can be used to assist thermal comfort and natural lighting. Incorporate passive design elements into a new or existing house which creates a more comfortable home to live in, save on its operating costs, as well as reduce its energy demand and greenhouse gas emissions.
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