Experimental and Theoretical Studies of Green Energy Building Using Various Building Materials and Orientation
Date
2016
Authors
Saboor, S.
Journal Title
Journal ISSN
Volume Title
Publisher
National Institute of Technology Karnataka, Surathkal
Abstract
The cooling of buildings by using passive methods has evoked great interest. Passive
cooling is one of the methods to keep the building cool and to reduce the load on the
air conditioner. The most prominent building elements that ensure energy efficiency
in buildings are building enclosures such as walls and roofs. Passive cooling demands
the study of the thermal characteristics of walls or roofs such as admittance,
transmittance, decrement factor, time lag, surface factor and surface factor time lags.
For the computation of these unsteady state characteristics, one dimensional heat flow
diffusion equation with convective periodic boundary conditions was solved using
matrix algebra and a computer program was developed using MATLAB to compute
unsteady state thermal characteristics of homogeneous and typical composite walls.
Natural building materials depreciate negative ecological impact and promote
environmental sustainability. Hence, it is imperative to dedicate attention to the
thermal performance of natural and sustainable building materials. Laterite stone is a
locally available and natural building material in South-West coastal India. The
thermal properties of laterite stone exposed to various humidity and temperature
levels of ambient air were measured experimentally and their impact on unsteady
thermal response characteristics of the laterite walls was studied in detail. The results
showed that the increase in the relative humidity from 0% RH to 98% RH decreases
the decrement factor by 8.35% and increases the time lag by 2.88%, whereas, the
increase in the temperature from 0oC to 60oC decreases the decrement factor by
14.5% and increases the time lag by 8.3%. The effect of thermal properties of
building materials, insulation location, air space thickness and air space location on
unsteady state thermal characteristics was studied. From this study, It is concluded
that fly ash brick composite walls with jute felt insulation located at the mid plane of
the wall give greater time lags (11.17h) and fly ash brick composite walls with coir
board insulation located at the outer side of the wall give the lowest value of
decrement factor (0.17) among hundred configurations of the walls studied. Optimum
wall thicknesses of building and insulating materials were computed. From the
results, it is concluded that mud phuska and coconut pitch are the most recommendediii
homogeneous building and insulation materials, respectively, among studied building
and insulating materials, from lower decrement factor and higher time lag point of
view. It is also found that the insulation materials are highly responsive to short wave
radiation than that of building materials. The impact of the divided air space thickness
within the wall on thermal performance of the wall was also investigated. From the
results, it is observed that the decrement factor decreases and time lag increases with
the increase in the divided air space thickness within the composite wall for all
building materials. The effect of unventilated continuous vertical air space location in
the wall on unsteady state thermal response characteristics of composite walls was
also studied. From this study, it is observed that Fly ash brick composite wall with air
space located at the outer side and the mid center plane and fly ash brick with air
space located at outer and inner sides of the composite walls are the recommended
composite walls due to their highest time lag (11.28 h) and lowest decrement factor
(0.166), respectively among studied building materials. The influence of the
insulation location in the roof on thermal performance was investigated. The results
reveal that the roof with insulation placed at the outer side and at the mid center plane
of the roof is the most energy efficient from the lower decrement factor point of view
and the roof with the insulation placed at the mid center plane and the inner side of
the roof is the best from highest time lag point of view among seven studied
configurations. The unsteady thermal response characteristics of hollow and stuffed
bricks were also studied. From the results, it is observed that thermal admittance,
surface factor time lag, decrement factor time lag and areal thermal heat capacity
values increase with the increase in the number of air gaps in hollow bricks, whereas
thermal transmittance and decrement factor reduces with the increase in the number of
air gaps in the hollow bricks. The effect of wind velocity on the dynamic thermal
performance of various composite walls was also reported. This research aids in
designing energy efficient and environment friendly buildings for passive cooling.
Description
Keywords
Department of Mechanical Engineering, Decrement factor, Time lag, Admittance, Surface factor, Optimum insulation thickness, Laterite stone, Optimum insulation location, Air space thickness, Air space location, Hollow bricks, Stuffed bricks, Wind velocity, Admittance procedure