Building Construction Book By Sushil Kumar Pdf 257 [PORTABLE]
It is also worth noting that both active and passive strategies for improving energy efficiency and reducing emissions in case of buildings are popular in North America and Europe, particularly among Scandinavian countries. Though it may be attributed to high per capita income in these countries making initial expense affordable to a majority of population, the climate also seems to have a role. For instance, buildings in cold climates have to employ strategies which would reduce energy consumed in heating the indoor space. However, in a sub-tropical and/or temperate climatic zone, buildings need to employ energy efficiency strategies for heating in winters and cooling in summers. This would mean additional investment which may lead to lifecycle cost for the energy efficient building higher than that for the conventional structure. This implies the necessity of studying climatic suitability of the proposed investment [11, 12]. Vernacular construction practices in the region are likely to provide a good solution, and they need to be explored as well.
Building Construction Book By Sushil Kumar Pdf 257
Based on above preamble, this article has the following objectives: (i) to review different strategies to improve energy efficiency and reduce emissions in buildings, with emphasis on passive buildings (Energy efficient and environment friendly buildings), (ii) to outline procedure for lifecycle cost assessment for passive buildings (Economic feasibility of passive buildings), (iii) to understand adaptability of passive buildings to diverse climatic zones and climate change (Climatic adaptability of passive buildings), (iii) to outline prominent standards related to construction of passive buildings (Standards on passive buildings) and (iv) to discuss present shortcomings and thereby explore novel research opportunities (Contemporary research). The article is likely to provide readers a holistic insight into the world of passive buildings, and thereby enable them to make informed choices while planning to build energy efficient and environment friendly buildings. The article will also help researchers in developing novel strategies for further improving energy efficiency and reduce greenhouse emissions, in case of buildings. The article hosts a good bibliography which will enable readers develop knowledge and understanding specific to their research interests.
Energy efficient and environment friendly buildings are commonly termed as green or sustainable buildings. United States Green Building Council (USGBC) defines green buildings as holistic buildings, which in planning, design, and operation have a positive effect on their surroundings. Such buildings consume minimum natural resources for their construction and operation throughout their design life, promotes reuse, recycling and utilization of renewable resources, and thereby reduce our dependence on non-renewable resources .
The traditional roof construction in Indian subcontinent used burnt clay units with mud mortar covered with a layer of terracotta tiles . This design has been very successful at shielding the indoor environment from the outdoor environment which can be extreme in tropical regions. However, in a bid to go higher, most modern buildings are using concrete slabs which have high solar absorption and longer heat retaining capacity. This tends to overheat the dwelling spaces in summers, and in turn increase energy consumption by HVAC systems [61, 62]. As a consequence, a number of modifications such as roof shadings, roof coatings or compound roof systems, have been attempted [63,64,65]. Another common roof in case of buildings with large plan area is lightweight aluminium standing seam roof. These roofs also have poor thermal characteristics, and need to be adequately insulated. The insulation layer can be composed of glass fiber, polyurethane, polystyrene or a mix of these, depending on the climatic zone of application [62, 66].
From the above discussion, it is evident that the choice of technology for walls, roofs and openings depend on the desired effect which in turn heavily depends on the climate of the site. It is obvious that use of any of these technologies is likely to increase cost of construction of the project. However, the initial investment will result into an energy efficient and environment friendly building, which will certainly reduce the cost of operating and maintaining the building. In the upcoming section, we will discuss how to estimate lifecycle cost of a building. Estimation of lifecycle cost would enable us to decide the level of optimal investment in passive buildings.
It is well established that passive buildings are solutions to menaces of energy crisis and ecological damage posed by the built environment. However, since construction is capital intensive, it is utmost important that solutions be evaluated for economic feasibility. This is much more relevant in case of residential buildings in developing world where people tend to spend much more than their liquid assets and end up taking institutional and non-institutional loans. These construction loan portfolios attract very high loss rates during economic downtime and are a key factor in failure of many banks . The severe economic threat posed by recent pandemic COVID-19 has forced individuals as well as federal governments to think in this direction.
Economic feasibility is usually assessed by estimation of lifecycle costs (LCC) associated with the building, which is the total cost of owning, operating, maintaining, and disposing of the building over a given study period. In order to compare economic feasibility of multiple passive alternatives against conventional non-passive construction (usually called base case), the future costs of operation, maintenance and disposal are converted to their present value equivalents. This process is called discounting, and is achieved using Eq. (1), where PV and FV respectively denote present value and future value after t years, and d denotes the discount rate. The process of obtaining compound interest forms the basis of the discounting process.
The study period for LCC refers to time over which costs and benefits related to a capital investment decision are of interest to the investor. Depending on investment routine and habit of the investor, the study period may be significantly less than the design life of the building. However, it must be considered the same for all the design alternatives being considered. The study period can be divided into planning-construction period and service period, as depicted in Fig. 6.
In 2000 and 2010, more than 95% and 70% of all passive buildings were located in Germany and Austria respectively . Though the concept seems to be spreading out, the spread has been mostly limited to Europe . There can be diverse reasons for this poor acceptability of passive buildings outside Europe especially in Asia and Africa. Most of the construction in Asia and Africa tend to reduce the initial cost of construction. As passive buildings are usually expensive than conventional ones, they are not sought in most cases. The other reason may be the extreme climate conditions prevailing in Asia and Africa. While passive buildings in Europe aim to achieve heating of indoor environment without over-reliance on active measures, such buildings in Asia and Europe have to achieve heating in winters and cooling in summers. This contrast in desired features of a passive building is difficult and more expensive to implement, and thereby passive buildings are not gaining enough popularity in tropical and temperate climate zones. It is also worth noting that most of the passive buildings in Asia and Africa are public buildings, unlike residential buildings in Europe . This suggests that governments in these regions are keen to achieve energy conservation and emission reduction in buildings and building construction industries.
Tropical climate is characterized by high temperature and high relative humidity. Cooling load in such places can become excessively high, which can be subdued only through proper ventilation. Therefore, the most useful passive design strategy is to maximize cross-ventilation and convective air flow. For industrial sheds and warehouses, clerestory windows located at higher levels can help hot air to escape. Wind-driven roof vents are also commonly used in industrial buildings to facilitate escape of hot air. These vents spin faster when outside temperature is higher, and do not need electricity for running. Further, lightweight materials with low thermal conductivity (such as fly ash blocks) should be used for walls and roofs. Cavity walls and ventilated roofs are suitable solutions to minimize solar gains. Solid walls made of heavy weight materials like clay bricks and concrete should be well-shaded as far as possible. Openings should have sunscreens to prevent direct solar gains. Chajjas (overhangs), pergolas and jaalis (perforated screens) are commonly used to screen away direct sunlight. Glazings in openings should have low solar heat gain coefficient (SHGC) and high visual light transmission (VLT), to ensure low heating and high daylight at the same time. Passive building designers usually aim for high ratio of VLT to SHGC. Ecological features like vegetation and lakes around the building are also go-to passive strategies as they act as heat and carbon sinks. Supply air ducts to cool and dehumidify the indoor environment are usually used. Air flow in supply air ducts consumes much less energy than using active measures like HVAC systems. Traditional construction in some regions include air channels and buried ducts, and should also be explored. There have been numerous studies for passive building design in tropical and sub-tropical climate [16, 18, 120,121,122,123,124,125,126,127,128,129,130,131] and arid climate [132,133,134] zones.
The aforementioned literature in this section helps us comprehend and consider parameters that are suitable to the regional climate and possibly accommodate to the climate change. However, the stakeholders including owners and construction companies will be confident about adopting passive buildings if the respective government prescribes standards and guidelines in this context. The upcoming section reports some of the prominent standards related to passive building construction from around the world.