The energy requirement of buildings can be reduced by the internal layout of the design
By making the best use of the sun’s radiation, the need for heating energy can be reduced. Spaces such as sunrooms, if located on south façades of buildings, also contribute to heating of the building and energy conservation, by storing solar radiation, says Nitin Pawar, Construction Manager, Turner India.
How does site selection and building orientation matter to energy efficiency in the pre building phase?
To make any building energy efficient, the pre building phase is fundamentally aimed at understanding and comprehensively studying the proposed function of the building with respect to various parameters such as location, surroundings, topographic and environmental conditions like sun radiation, air temperature, air circulation, and humidity, etc. The pre-construction stage is essential to make building efficient. This stage includes design, site selection and determining building type, building layout, and building envelope. Design of the building must consider maximum use of local and energy efficient construction materials, efficient building envelope and landscape.
The location and distance of the building from the surrounding buildings are very important design parameters, which can create impact through two major renewable sources of energy, i.e.sun radiation and air circulation velocity around the buildings. For this reason, the site of the building in the area should be determined to benefit and defend from the renewable energy resources like sun and wind. In order to provide suitable protection from the major energy sources, the orientation of the buildings is again a decisive parameter with respect to the climatic conditions of the region. In cold regions, lower overnight temperatures cause colder, denser air to accumulate in hollows and valleys. Therefore, in cold regions it is advisable to position buildings on hillsides rather than in valleys.
The topography and location of the building are critical aspects because of the effect of angle of incidence on solar radiation, slope, and orientation of the land in terms of the use of daylight, natural ventilation, and solar radiation. If the settlement will be sloping, gained solar radiation energy is reduced in summer, and increases in winter. In the design of buildings, distance between buildings is another important designing parameter that affects utilization of solar energy, wind direction, and speed concerning artificial environments.
What is the role that climate plays in attaining energy -efficiency, in which stage of the construction process does it need to be addressed?
Climate plays a significant role in the energy efficiency patterns in different areas, and it must be a factor to be considered right from the pre-construction stage. It is well known that the south slope is warmer. When a choice of site is available, a south slope is preferred for most building types. In the winter, the south slope is the warmest land due to two reasons: (1) it receives the most solar energy on each square foot of land because it most directly faces the winter sun, and (2) the south slope also experiences the least shading because objects cast their shortest shadows on south slopes. The south slope gets the most sun and is the warmest in the winter while the west slope is the hottest in the summer. The north slope is the shadiest and coldest, while the hilltop is the windiest location. Low areas tend to be cooler than slopes because cold air drains into them and collects there.
For envelope-dominated buildings, such as residences and small office buildings, the climate is a major consideration in determining the sites. For example, in cold climates, south slopes maximize solar collection and are shielded from cold northern winds. The windy hilltops and low-lying areas that collect pools of cold air must be avoided. In hot and dry climates, one must build in low-lying areas that collect cool air. If winters are very cold, the building must be on the bottom of the south slope.
If winters are mild, one must build on the north or east slope, but in all cases the west slopes must be avoided. In hot and humid climates, one can maximize natural ventilation by building on hilltops but must avoid the west side of hilltops because of the hot afternoon sun. In addition, the cool low-lying areas are appropriate especially to the north of hills. For internally dominated buildings, such as large office buildings that require little of any solar heating, the north and northeast slopes are best.
How does the total solar radiation gain of a building impact the energy efficiency desired in the long-term, how can this be offset?
Several factors such as the building altitude lead to differentiation of solar radiation values. As we go above the sea level, we get an increase in solar radiation values. In return, for the increase in solar radiation values, as we go above the sea level, we get a decline in the air temperature. With the increase of altitude, gale force also increases, which leads to the increase of heat loss in the building.
The fact that a building remains within the shading space of other buildings influences the utilization of solar rays and raises the consumption of energy. In order to utilize solar radiation, building spaces must not be less than the tallest shade height of other buildings. Orientation of building affects the ratio of the solar radiation gain of building sides, and consequently the total solar radiation gain of building.
Spaces such as sunrooms, if located on south façades of buildings, also contribute to heating of the building and energy conservation, by storing solar radiation. In hot and dry climate zones, flat roofs should be preferred to reduce the impact of solar radiation. Since protection from solar radiation and wind is the primary purpose in hot and arid climatic zones, small and few windows should be used. Yet, in order to utilize the beneficial effect of solar radiations, the window openings in the southern front should be kept more than the ones in other fronts.
It is possible to produce heat and electricity with solar energy in buildings using such equipment solar collectors, photovoltaic (PV) panels, and building integrated PV (BIPV). The potential application of PV panels in high-rise buildings is more than the low-rise buildings because of higher neighboring buildings; it gives more possibility for direct solar radiation. Requirements for regulation of large amounts of PV panels are the most important problem. Because it is necessary to maintain aesthetics and PV panel’s productivity in buildings.
The active systems where solar energy is used are the systems composed of the aggregation of mechanic and/or electronic components that convert solar radiation absorbed via collectors produced for this end into energy in a desired form and permit this to be used in building. Through these systems, solar radiation can turn into heat and electric energy These systems that transform solar radiations into energy are divided into two according to the energy they produce: solar thermal systems producing thermal energy and thermal electric (photovoltaic) systems (PV systems) producing electric energy.
How is the energy performance of a building affected by form, volume, surface rate and frontal motions?
Energy performance of a building is affected by such factors as its form, volume surface rate and frontal motions. There is a direct relationship between the geometrical shape and energy performance of building. The shape of the building which is a considerable factor affecting heat loss and gain can be defined through geometrical variables making up building such as the proportion of building length to building depth in the plan, building height, type of roof, its gradient, front gradient, etc.
In several studies, it has been observed that different results were obtained in the energy performance of structures that had the same volume but made in different forms or having different climate conditions. In colder regions, compact forms should be used which minimizes heat loss. In hot-dry regions, compact forms and courtyards should be used which minimize heat gain and help to provide shaded and cool living spaces. In hot-humid climate regions, long and thin forms whose long side is oriented to the direction of prevailing wind makes maximum cross-ventilation possible. In mild climates, compact forms, which are flexible more than the forms used in cold climate regions, should be used.
Building plans and shapes should be effective in energy conservation. Therefore, buildings should be formed to ensure minimum heat gain in warm seasons and maximum in cold. Due to simple plan types such as square or rectangle having a reduced surface area, their heat-loss and -gain are also reduced. Smaller buildings, where internal space has been used efficiently, less energy must be used as they can be heated, cooled, and illuminated more efficiently than larger buildings.
The energy requirement of buildings can be reduced by the internal layout of the design. By making the best use of the sun’s radiation, the need for heating energy can be reduced.
Spaces such as sunrooms, if located on south façades of buildings, also contribute to heating of the building and energy conservation, by storing solar radiation. Thermal zoning and the settlement of indoors can be designed in a way to raise mutual air motion. Deep plans and the use of too many dividing elements may restrict air motion in environments.
Building envelope includes the components such as wall, ceiling, ground, window, and door that separate the building from the outdoors and transfer heat energy inside and outside. As an indoor and outdoor element, it has a vital impact on energy consumption. While the cost of constructing a building envelope makes up 15–40% of the total construction cost, its contribution to life cycle costs especially to energy cost is around 60%. The skin of the building performs the role of a filter between indoor and outdoor conditions, to control the intake of air, heat, cold, and light. Building envelope should minimize the heat loss in the winter and the heat gain in the summer.
The shape, material, gradient, orientation, outer surface color, and insulating qualities of the roof also determine the thermal performance of the buildings. Besides, through an accurate and conscious energy protected landscape design, it is possible to reduce the energy cost spent for heating and cooling during summer and winter seasons by 30%.
What according to you are some of the renewable energy resources which can help a building in attaining energy-efficiency?
Sun, wind, biomass, biogas, geothermal energy, hydro, wood, ocean thermal, sea flows are the inexhaustible energy resources that can be used by all living creatures on earth. It is possible to benefit from renewable energy resources with both passive and active methods.
Passive heating: Passive solar heating systems are categorized by the relationship between the solar system and the building. There are three categories of passive solar heating systems: direct gain systems, indirect gain systems, and isolated gain systems. In the passive solar heating system, building elements (windows, walls, floors etc.) collect and store heat and then distribute it in the indoor space. The direct gain passive solar building has windows that admit the winter sun directly into the occupied space. These solar gains serve to either meet part of the current heating needs of building or are stored in the thermal mass to meet heating needs that arise later. An indirect gain passive solar system has its thermal storage between facade and the indoor spaces.
Heat is collected and stored in an exterior wall or on the roof (with water or brick/concrete) of a building, and distributed to the indoor. Isolated gain passive solar concept comprises solar collection and storage that are thermally isolated from the indoor space of the building. The most common use in isolated gain systems is a sunspace. Collection and storage are separate from the occupied spaces but directly linked thermally. A sunspace is a room attached to or integrated with the exterior of a building in which the room temperature is allowed to rise and fall outside the thermal comfort zone.
The active use of solar energy systems in buildings: The active systems where solar energy is used are the systems composed of the aggregation of mechanic and/or electronic components that convert solar radiation absorbed via collectors produced for this end into energy in a desired form and permit this to be used in buildings.
Through these systems, solar radiation can turn into heat and electric energy These systems that transform solar radiations into energy are divided into two according to the energy they produce: solar thermal systems producing thermal energy and thermal electric (photovoltaic) systems (PV systems) producing electric energy.
The active use of wind energy systems in buildings: Recent developments in this technology have allowed wind turbines to be utilized in building design. Consistent with the high performance approach to building design, the use of wind turbines on high buildings is significantly enhanced by their integration with the building architecture.
Use of geothermal energy in buildings: Geothermal energy is used in heating and cooling in houses, greenhouse cultivation, and agriculture. Geothermal energy systems are applied in three different ways according to application methods such as heat pumps, downhole heat exchangers, and heat pipes. Their common usage in buildings is in the form of heat pipes.
Use of hydrogen energy in buildings: Hydrogen energy can be used for heating houses, providing hot water, cooking and meeting electricity needs. In order to use hydrogen here, we first need to produce it, then store and transfer it. Hydrogen can be produced from such renewable energy sources such as sun, hydroelectric, wind, and geothermal.
Use of biomass energy in buildings: Biomass is a strategic energy resource, which is renewable and environment friendly, can be grown everywhere, enables socioeconomic improvement, and can be used for power generation and for obtaining fuel for vehicles.
Natural lighting: Natural lighting in buildings is carried out through windows and skylights. Choice of direction in the windows and roof lighting is important. The most suitable directions for natural lighting are south and north. The north direction is not exposed to radiation, but can always get daylight in the same quality. In the west and east directions, the sun radiates in horizontally and makes it difficult to control. In the south direction, the effect of the sun is permanent and the sun rises at a right angle compared to the west and east directions.