Performance evaluation of shading devices used in tall office buildings of Dhaka city

Abstract

One of the characteristics of to.lloffice building:; in nhah city i< the extensive uoe of glazing on d,e bwlding facades. This inct~a,ing U3e of glaS3 has cau3ed con:;iderable changes in the relation3hip b~tv.'een interior and ambient dimate, where the problem of overheating ha3 become a major concern. So facades of tall building< need protection from soJar heat gam to achieve desitable indoor env;ron.meot and to reduce the enetgy consumption ill the building" by the air conditioning "ystem. External shading devices c.~n be utili,ed to block the ,olar rac.ltltion before it teaches the window surface and hence more effective than intetrull shading deviccs. The ptoblem was approached by performance evaluation of sclccted commonly used shadIng devices of tall office buildings through simulation study_ Shadow simulation alIo", stud)' of the effect of changes in one aspect, keeping other factots con,tant. The observations of simulated performancc that occurs due to changing parametcrs allow the identifiotion of elements, the reduction or introduction of which in the design contnbute to solar heat gain. Through simulation study, it is possible 10 analyse the performance of shading devic~' for any period of the yeat. The simulation .luille. were conducted fot the months from March to September repcc.enring hot-dry and warmhumid period, which is mo,t .ignificant in term. of dimatic severity. Th~ .imuffition studics were performed tu evaluate perfonnances of .hading devices and identifY thc effects of different par-Mneter3 and correffition among parametet' in tcrm. of reducing soIM heat gain. 1Oi•• tudy also helped to understand the influence of window orientation on the performance of shading dcvices, Aftet all the imTstig.J.tions and critical ",-aluanons, a parametric srudy to explore the strategies fot optimL1m shading wa3 pursued through a series of .,imulations a, solar geomet'}. is a I'teructable phe<lomenon and much of its impact is quantifiable. Parametric 3rudy allow, "tud)' of various a1t~rnatives ",~th reference to perfoonance of the model and identifying thc best one. Rased on the parametric study, desj~ reconuncndauons and de,i~ gmdelines W~rt,derived. The findings of thl3 thesis ar~ concerned with the problem of soht heat gain jn tall office buildings in tropical climate hke Dhaka eity. 'Ine rc,uh, of the simulation 3rudies and patametnc srudic" ha,e been expr~,«ed in tern" of " number of climate re3poll.i,-c shading d~,ign guidelines. It is expected that th~ application of these gwdelincs ",ill reduce solar h,'at gain in comparison to that of pres en, ptactices.