Optimizing the position of insulating materials in flat roofs exposed to sunshine to gain minimum heat into buildings under periodic heat transfer conditions

Abstract

Building roofs are responsible for the huge heat gain in buildings. In the present work, an analysis of the influence of insulation location inside a flat roof exposed directly to the sun's radiation was performed to reduce heat gain in buildings. The unsteady thermal response parameters of the building roof such as admittance, transmittance, decrement factor, and time lags have been investigated by solving a one-dimensional diffusion equation under convective periodic boundary conditions. Theoretical results of four types of walls were compared with the experimental results available in literature. The results reveal that the roof with insulation placed at the outer side and at the center plane of the roof is the most energy efficient from the lower decrement factor point of view and the roof with insulation placed at the center plane and the inner side of the roof is the best from the highest time lag point of view among the seven studied configurations. The composite roof with expanded polystyrene insulation located at the outer side and at the center plane of the roof is found to be the best roof from the lowest decrement factor (0.130) point of view, and the composite roof with resin-bonded mineral wool insulation located at the center plane and at the inner side of the roof is found to be energy efficient from the highest time lag point (9.33 h) of view among the seven configurations with five different insulation materials studied. The optimum fabric energy storage thicknesses of reinforced cement concrete, expanded polystyrene, foam glass, rock wool, rice husk, resin-bonded mineral wool, and cement plaster were computed. From the results, it is concluded that rock wool has the least optimum fabric energy storage thickness (0.114 m) among the seven studied building roof materials.

Thermal Behaviour Analysis and Cost‐Saving Opportunities of PCM‐Integrated Terracotta Brick Buildings

“…), as it simultaneously takes into account the thermal conductivity, the specific heat capacity, and the density, under periodic thermal conditions. A lower unsteady-state thermal transmittance value signifies a higher thermal resistance and thermal mass [39][40][41][42][43]. e steady-state thermal transmittance U s indicates the heat transfer rate through a building configuration.…”

Smart buildings as Cyber-Physical Systems: Data-driven predictive control strategies for energy efficiency

“…For example, the thermal interdependencies between building zones could be derived from a wall's thermal admittance [141] and its materials. These parameters determine a wall's decrement delay (time lag between the timing of the temperature peaks at either of the wall's sides) and its decrement factor (dampening the temperature peak of one side of the wall to the other) [142]. That information should lead to the appropriate history lengths and inter-feature lags.…”

Comparative Study of Monte Carlo Simulation and the Deterministic Model to Analyze Thermal Insulation Costs

“…In their proposal, they considered the unstable thermal response of the building roof, such as admittance, transmittance, decay factor, and time delays, through a one-dimensional diffusion equation under convective periodic boundary conditions. The theoretical compared with the experimental results of four types of walls are available in the literature [16].…”

“…The proposal was tested for three buildings characteristic of the existing building heritage. The results showed that the behavior of the three envelopes differs greatly because they interact in unique ways according to In the literature, there are many studies on the optimal insulation in walls; for example, Shaik and Talanki [16] analyzed the influence of insulation location within a flat roof directly exposed to solar radiation to reduce the heat gain in buildings. In their proposal, they considered the unstable thermal response of the building roof, such as admittance, transmittance, decay factor, and time delays, through a one-dimensional diffusion equation under convective periodic boundary conditions.…”