Thermal Performance of Building Envelope

In the era of raising environmental problems, built structures are considered as one of the main energy consuming entities which are ultimately responsible for environmental degradation. To handle the issue it is important to deal with building’s energy demand which is mainly due to extreme weather conditions. Building envelope is the first to encounter with weather thus it plays a major role in deciding building’s energy demand. This paper deals with the improvement of thermal performance of Building Envelope according to climate, indices and local solar time of region .This paper also focus on new facades technologies which lower down the building’s energy demand with better insulation. To achieve this goal an integrated approach is required which comprise techniques, technologies, architectural innovation all together. These facades also have benefits other than energy saving . Numerous technologies are being developed to generate energy also.


INTRODUCTION AND STATEMENT OF THE PROBLEM
Heat transfer from outside to inside takes place through the Building Envelope and the quantities are derived through certain basic principles. The purpose of this paper is to find out the appropriateness of various principles according to the climate and methods to do the climate analysis. The paper will also give the measures for the overall performance of Building Envelope and Building envelope techniques to reduce the energy consumption .
BACKGROUND & CONTEXT Numerous researches have been done on quantification of various parameters of heat transfer but each parameter will not be giving the same results in each & every climate and for designing, the designers should know the fundamentals of these parameters and which parameter they should focus more on in terms of achieving the required outcome for a specific climate.

The goals of this technical paper are:
• To find out the Impact of Solar time and local clock time on received solar radiation in different directions by giving an example • To know about the indices of assessing Thermal Performance of Building Envelope • Actual Meaning of the indices and to figure out whether all the indices are affected by design/orientation, material and the amount of solar exposure. High performance building facades are building envelops that use minimum amount of energy to maintain comfortable indoor environment for occupants as well as improves occupant's health and productivity. High performance facades don't act as barrier between interior and exterior environment rather they participate as active systems in minimizing building energy consumption by responding to external environmental conditions. As climate plays a vital role in building energy performance all guidelines related to climate must be taken into considerations while designing 'High Performance Building Facades' Design Strategies for high performance facades in 'Hot & Humid' regions are quite different from those in 'Hot & Arid' regions. Building Facades affects building's energy bills and occupant's health more than any other system. In summer solstice, Typically we get sun right above the head, it never crosses towards the Northern side. The sun is slightly tilted towards south, but still, during the morning and evening times, we get sun from the north east and north western side

METHODOLOGY
In Winter solstice December 21st here we have typically the least possible altitude angle. We do not get sun directly on the east or west, it is mostly somewhere close to south-east and south-west and it has a Southern traverse, this is the case of 34 degree north latitude.

Some Definitions: Thermal Efficiency of Envelop is to be considered at Element level, Component Level and Assembly level
Thermal mass is the capacity of material to absorb, store and release heat.
Heat Capacity is the ability of wall to store heat. Heat capacity is used for quantifying the amount of thermal mass in a wall.
Thermal Lag: When in comparison to the peak time on exterior , time of peak temperature and heat gains on interior is delayed, then this phenomena is called Thermal Lag 2 1.Thermal Transmittance :Thermal transmission through the unit area of a building unit divided by temperature difference between the air on either side of the building unit

Requirement of U Value acc. To climate:
U Value is the basic essential quantification measure for every climate but not just the one through which thermal efficiency is obtained. For example : If we take two same walls of same thickness i.e. 150mm RCC wall with insulation near to the outer skin and insulation near to interior skin, the U Value will remain the same, but there will be a change in TTC. NBC also prescribes minimum TTC value accrding to the climate.