Hybrid and Reflective Insulation Assemblies for Buildings

David W Yarbrough,Lim Chin Haw,Elias Salleh,Khar San Teh,M Yusof Sulaiman,Sohif Mat

doi:10.4236/jpee.2016.47004

Abstract

Materials with a low thermal emittance surface have been used for many years to create reflective insulations that reduce the rate of heat flow across building envelopes. Reflective insulation technology is now being combined with other energy conserving technologies to optimize overall thermal performance. The basis for the performance of reflective insulations and radiant barriers will be discussed along with the combination of these materials with cellular plastic or mineral fiber insulations to form hybrid insulation assemblies. Calculations of thermal resistance for enclosed reflective air spaces and current field data from Southeast Asia will be presented. These data show that reductions in heat transfer across the building enclosure can be effectively reduced by the use of enclosed reflective air spaces and attic radiant barriers. Reflective technology increases the overall thermal resistance of the building enclosure when used to insulate poured concrete structures.

Highlights

Enclosed reflective air spaces have significant thermal resistance making them useful as thermal insulation for a building enclosure
The thermal performance of radiant barrier system (RBS) is generally determined from computer simulations of the heat flow and air movement in the ventilated space [13]-[15]
The thermal resistance attributed to enclosed reflective air spaces is readily calculated from published correlations representing a large number of hot-box tests

Summary

Introduction

Enclosed reflective air spaces have significant thermal resistance making them useful as thermal insulation for a building enclosure. The term reflective air space means that there is at least one surface with low emittance (emissivity), ε, perpendicular to the direction of heat flow. The radiative heat flux, qrad, across an air space The radiative heat flux, qrad, is readily calculated from the above equations for large parallel surfaces and used to estimate the radiative flux for enclosed regions in the building enclosure. The total heat flow across an air space includes conduction and convection in addition to radiation. Convective transport is often negligible and the sum of radiative and conductive heat transport can be readily calculated [4].

Total Heat Flow across a Reflective Insulation Assemble

Radiant Barriers and Ceiling Heat Flux

Field Testing of Radiant Barrier Systems in Malaysia

Hybrid Assemblies that Include an Enclosed Reflective Air Space

Conclusion