Effect Of Stochastic Adjustment Of Solar Shading On Indoor Thermal And Visual Conditions

Among building energy efficiency measures, solar shading plays a significantrole in reducing energy consumption and in improving indoor thermal and visualcomfort. Currently, manually controlled adjustable solar shading is mostly used inbuildings in China, which challenges an accurate analysis of its impact on buildingsdue to the stochastic character of user behavior. Thus, it is very important to give aninsight into the user behavior on manually adjustable solar shading.In this paper, a typical office building in Ningbo was selected to carry out solarshading state record by photograph as well as outdoor temperature and solar radiationmeasurements. Five solar shading states (including shaded window areas of0%,25%,50%,75%and100%) were considered to take a cumulative odds logit analysis andresults show that solar radiation is the major factor in driving shading switch. Then astochastic model for adjustable solar shading was constructed by using Markovmethod and was also modeled in BCVTB for coupling simulation with Energyplus todo building performance analysis.The energy performance and indoor thermal and visual comfort for the typicalbuilding were simulated based on the above model. Results show that externaladjustable solar shading has the best performance, followed by the internal one andLOW-E double-pane windows, and double-pane windows perform relatively poor interms of indoor base temperature, solar transmittance, energy consumption andPMVradand PPDrad(a more accurate index considering solar radiation on human bodybased on PMV-PPD). The indoor comfort time of external adjustable solar shading ishigher than LOW-E windows by6%-20.8%and higher than double-pane windows by20.5%-49.7%.According to different objective and subjective evaluation indexes, adjustablesolar shading improves indoor visual comfort significantly. Useful DaylightIlluminance on work plane for adjustable solar shading is about2-3times much betterthan LOW-E windows and its illuminance fluctuation also performs better. Adjustablesolar shading has advantages in controlling high contrast at view direction. UsingRadiance and Evalglare, DGI and DGP indexes which consider human eye adaption to light density were introduced to give a detailed analysis on visual comfort. Resultsshow that adjustable solar shading performs mostly better than LOW-E windows,especially for external ones which have a20%reduction of glare on west facade andabout4%for east and south facades, and reduce untolerable glare by1/2to2/3.