The effect of general form and relative compactness of Tehran residential buildings on pollution redulted from heating in winter season

1.Introduction consumption of several fossil fuels lead to increased pollutants like CO2. House buildings are high consuming subscribers and around one third of national energy is consumed by them. The Iranian architecture with several territorial areas in different seasons has invented and offered rational ways to provide welfare condition of human being. Since regress to the past building methods is not easy and certainly is not accountable for our present life condition, research on the field of designing according to territory by inactive method seems necessary. The main purpose and trend of in designing compatible to territory is the least use of mechanical systems and decrease energy consumption for heating, chilling and the most use of radiation energy. One of the ways of decreasing energy use in this climate condition is to increase absorption of radiation energy through the transparent level of the external cover in the south façade in the cold season. The windows provide the facility of receiving free solar energy and improve the condition of heat and visual welfare for the habitants of the building. Regarding the common technologies in country building industry there is need to understand optimal ratio of window to the wall. In this study considering the existing statistics about the residential units and rate of population, the necessity of identifying several types of residential common buildings and their relative aggregate have been considered and will be examined. Computer simulation and field survey have been the main trend of this study. The software of Design Builder calculates the energy consumption rate using the calculation motor Energy Plus. 2. Methodology This research has been carried out based on library and field studies and from the commercial software of radiant energy have been used to obtain the result. Case study is Tehran residential common buildings that according to the descriptive design of 2012 is considered as 5floor buildings. To calculate the types, field observations and air maps of google earth have been used and by applying the theory of theoretical saturation and comparative adaptation it has been developed. The residential width that is the problem of the present research includes the main application in Tehran. In field calculation of descriptive design of Tehran in 2012, of 997 residential application, the average aggregate with 403 number has allocated the most number to itself. Based on this modeling of the research with 5 floor aggregate has been considered. Also in this research to recognize compactness of building volume, relative aggregate index has been used. The studies carried out in the field of identifying lack of knowledge shows that the rate of RC is optimal and morphology based on it is a basic step in guiding general form especially guiding architecture design based on it. The most compactness of volumes is the geometric shape of sphere with RC equals to 1. As most of the buildings are orthogonal polyhedral, square shape has been the work base which relative aggregate of the established morphologies is calculated with the following formula. The geometry compactness and relative compactness has come to this conclusion that RC is the most influential concept on energy efficacy. In this regard, energy efficacy will be interpretable that the equation 1 for this RC:6.V0.66.A-1 3. Modeling As the maximum height of residential buildings in Tehran is usually up to 5 floors, the height is divided into 5 parts and in proportion to Tehran lands, the length 6 parts and width 4 parts are also selected. In this article, in order to calculate heat load the software of design builder has been used that by inputting climate data in each hour for every territory, the needed heating load is estimated. In order to estimate the effect of architecture design and the elements used in the building on the demand rate to heating energy, an apartment with 5 one unit floors in Tehran has been selected and the rate of needed heating energy has been calculated through modeling in software of design builder. the ratio of window to the wall introduced in 10 types in 3 different states of 10, 25, 40 percent has been modeled in software of design builder. In the following, the optimal states of heating load regarding the ratio of opining to the wall in different types will be calculated and analyzed. 4. Discussion and result analysis One of the influential factors in the building sector in increasing pollutant Co2 is increasing energy consumption and as the most energy loss in the building occurs through external facades, the necessity of considering to this façade makes sense. As in climate condition of Tehran in cold months of the year, the rate of energy consumption in order to supply the temperature of heating welfare increases, so the necessity of considering heat load in these months increases. Modeling in 10 types and three states of window to wall ratio leaded to the analysis of 30 types ,and for heating load and Co2 emission characters in the software of design builder, that were evaluated in 6 cold months in Tehran. heating Figure 2 shows the graph of 10 building types and the rate of heat load and Figure 3 shows the graph of 10 building types and the rate of Co2 emission in 6 cold months of the year by the ratio of 10%, 25%, 40% window to the wall. (figure2,3). In all the graphs, in the months January and February the most heating load and Co2 emission and in the months of November and April the least heating load and Co2 emission are observed. In the graph of heating load and Co2 emission with WWR=10,25,40 the type of 4 has the least heating load and Co2 emission in average of cold months in Tehran. The type of 7 with WWR=10 and the types of 6 and 10 with WWR=25,40 have the most heating load and Co2 emission in average of cold months in Tehran. 5. Conclusion Regarding that the increase of heating load leads to increase of energy consumption and the increase of energy consumption leads to more pollution, in the present study that has been carried out on 10fold types for Tehran residential buildings, the following results have been obtained: 1. By focusing on the graphs of heating load and Co2 emission, altogether more heating load increase Co2 emission increase more and more heating load decrease Co2 emission decrease more. 2. As increasing wondow to wall ratio (from 10 to 40%), heating load and Co2 emission decrease. 3. In general, as the relative compactness of building increases, its heating load and Co2 emission decrease. Finally, it was observed that though in general the rate of WWR 40%, the best result is obtained in the rate of heating load and as a result the rate of pollution caused from heating in cold season, but to reach to more exact result it could consider the factors like orientation and self-shadowing in order to decrease heating load and as a result lowering the rate of pollution caused from heating in winter season.