Hybrid and Reflective Insulation Assemblies for Buildings

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.

Controlled TiO2 coating on hollow glass microspheres and their reflective thermal insulation properties

Hollow glass microspheres(HGMs)have great potential in building energy-saving and industrial insulation.Anatase TiO2-modified HGMs were prepared by a sol-gel method in acetic acid-ethanol solution.Scanning electron microscopy,X-ray diffraction,zeta-potential measurements,nitrogen-sorption measurements,and Fourier-transform infrared and ultraviolet-visible-near-infrared diffuse reflectance spectroscopies showed that the alkali modification of the HGMs greatly influenced the loading and microstructure of the TiO2 film.The TiO2 loading could be accurately controlled by ethanol addition and the TiO2 coating time.A mechanism for the TiO2 coating of the HGM surface is proposed.The synergistic action of hydrogen bonding and electrostatic forces resulted in close contact between the HGMs and TiO2 sol at pH 3.5.The effects of different TiO2 loading rates on the reflective and thermal insulation properties were studied.The near-infrared reflectance of 15.9%TiO2 coated on HGMs was 96.27%,and the inner surface temperature of the composite pigment coated on aluminum board was reduced by 22.4℃.The TiO2/HGM composite pigments exhibited excellent solar reflective and thermal insulation properties,so have potential in the construction of exterior walls and roofs.

Dynamic performance and energy efficiency of reflective and insulative composite coating on building exterior wall

Reflective and insulative composite coatings are a new energy-saving material with high solar reflectance and extremely low thermal conductivity for buildings.The optimization and impact of high solar reflectance and low thermal conductivity on the insulating capacity of walls remain uncertain.This work investigates the dynamic thermal performance and energy efficiency of a reflective and insulative composite coating in regions with hot summer and warm winter.A simplified thermal resistance-heat capacitance model of an exterior building wall is established to predict thermal performance.The dynamic temperature and heat flow of the wall are predicted to reduce heat loss through the interior surface of the wall and compared to the conventional coating.The specific impact of the thermal conductivity and solar reflectance of the coating on the heat loss is further investigated to minimize heat loss of the wall.This research shows that the composite coating shows better performance on adjusting outdoor climate change than the other coating.Compared with cement,it reduces the maximum temperature of the exterior surface of the wall by 7.45°C,and the heat loss through the interior surface of the wall by 38%.The heat loss is reduced with the increase of solar reflectance and the reduction of thermal conductivity.The results can provide a useful reference and guidance for the application of reflective and insulative composite coating on building exterior wall to promote their energy-saving use on building envelopes.

High-reflectivity high-contrast grating focusing reflector on silicon-on-insulator wafer

A high-contrast grating（HCG） focusing reflector providing phase front control of reflected light and high reflectivity is proposed and fabricated.Basic design rules to engineer this category of structures are given in detail.A 1550 nm TM polarized incident light of 11.86 mm in focal length and 0.8320 in reflectivity is obtained in experiment.The wavelength dependence of the fabricated HCGs from 1530 nm to 1580 nm is also tested.The test results show that the focal length is in the range of 11.81-12 mm,which is close to the designed focal length of 15 mm.The reflectivity is almost above 0.56 within a bandwidth of 50 nm.At a distance of 11.86 mm,the light is focused to a round spot with the highest concentration,which is much smaller than the size of the incident beam.The FWHM of the reflected light beam decreases to 120 nm,and the intensity increases to 1.18.