8/11/2019 The Sun and Building

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1. Designing for the Sun1.1 The solar effect on buildings

The sun affects buildings and their users principally in the following ways:-

DIRECT SUNI!"T INDIRECT SUNI!"T

#RC"ITECTUR#C$NCERN

Ther%al content &Infra red%ainly'

(isual content&(isualspectru%'

"ygienic content &ultra)iolet'

Daylight use&pleasantnessand sa)inglighting energy'

Reflection* re-e%itted fro%other sources

#s constituents ofsolar energy %a+or %oderate %inor %oderate %inor

Naturally )entilatedbuildings* for allseasons

desirable in ,inter &to war%the building' desirable in Spring - to drythe building* illing %ouldacceptable in #utu%n not desirable for prolongede.posure in Su%%er &i/e/ 0uneto %id $ct' to a)oid o)erheatingthe buildings

desirable*howe)er glareto be a)oided

desirable* e.cept where U(discolours paintings

desirable glare to bea)oided

#ir conditioned

buildings

desirable for periods in whichartificial heating would beneeded not desirable for periods inwhich #1C is needed

dependingon acti)ities notdesirable ifglare isaffecting theacti)ities

desirable desirable glare to bea)oided

2ost plants insideand outsidebuildings

desirable desirable desirable desirable i%%aterial

Specific se%i-indoor acti)ities -e/g/ solar therapy

desirable yearly - ditto - - ditto - - ditto - - ditto -

Indoor1outdoorfunctions e/g/ sun-drying of clothes

desirable yearly desirable desirable desirable i%%aterial

2ost outdooracti)ities

not desirable in o)erheating

periods of the day in Su%%er*Spring and #utu%n* desirable in,inter

desirable* but

glare to bea)oided

desirable to ha)e sufficient

a%ount on hu%an body*Not desirable if U( toostrong or too %uch &- InSu%%er* fro% 33 a% to 4p%* stay under a tree5'

desirable desirable*

howe)er glareto be a)oided

1.2 Understanding the sunpaths in relation to the buildings - Latitude - 22.37N passing through Shatin(ariables: day of year* periods in the day &apparent solar ti%e* standard ti%e - watch ti%e' - Su%%er ti%ewith the watch to ad)ance one hour6' in which direct sunlight is desirable1not desirable for which locationsinside and outside the buildings* and how to achie)e this6

7 INS$#TI$N - Incident Solar RadiationTools for studying INS$#TI$N &other than the 8uantitati)e aspects':-

Solar charts and shading protractors for certain shading de)ices

Table of solar declination angles

E8uations lining ti%e* day* latitude* solar a9i%uth angle* and solar altitude angle "eliodons: -

Dufton and ecett heliodons* ;hilips solarscopes* ;aul ittle Solu. de)ice*

new heliodons for laboratory* and architects< office &pending release'

1.3 ossible solar shading design for building - interior! "hen insolation #ther$al aspect% is not desirableThe rationale is:- do not let the ther%al content of solar radiation go into the interior S;#CE directly throughthe windows and openings and indirectly through the walls and roofs/

=i.ed shading de)ices: o)erhangs &hori9ontal or otherwise'* fins &)ertical or otherwise'* pergola* plants* air-

)entilated asse%blies of double wall1wall* wall1panel* glass1glass* with air1gas gap in between shading byother buildings and other parts of sa%e building/

type of building %aterials - absorbing1reflecting> glass type

%o)able1retractable de)ices* sun shields* curtains* blinds* %ulti-perfor%ance windows

water cooling techni8ues - e/g/ rain water through e%bedded tubes in walls* water heating solar panels for

hot water use

Solar energy collectors for generating electricity1heating as sun shades

The i%portant point is that for naturally )entilated buildings* both the windows &4?@ - A?@ of wall surface'and the ,all and Roof &B?@ - ?@' of en)elope area are to be considered for insolation design/

8/11/2019 The Sun and Building

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2. Designing for Natural &entilation

2.1 The need for natural 'entilationThe need for natural )entilation is su%%arised as follows:

T"E =UNCTI$NS $= N#TUR# (ENTI#TI$N

T"E NEED taing away heat taing away %oisture i%pro)ing indoor air 8uality &to controlconcentration of

gases1)apours1hu%an odour'

"u%an acti)ities so%e fresh air needed so%e fresh air needed re8uire the largest a%ount of fresh air

itchen-cooing e.tract it close fro% itssource reuse of this waste heat6

tae it away close fro% itssource to a)oid war%%oisture condensation oncold surface

to replenish the e.tracted a%ount

Toilet1bathroo%s - ditto - if hot waterbath1showers tae place

- ditto - especially showers all roo% air to be e.tracted to openair* and not to %igrate to other parts ofhouse replenishing air needed

Tobacco s%oing i%%aterial i%%aterial a huge a%ount of fresh air needed

#cti)ities that generate heate/g/ boiler roo% in hotel/

e.tracted to outside use of waste heat6

i%%aterial to replenish a%ount e.tracted

2.2 So$e thoughts of design for natural 'entilationEnergy free )entilation is always desirable/ In fact the least energy consu%ption the best - to sa)e %oney and to%itigate all sorts of ad)erse en)iron%ental effects due to energy consu%ption such as pollutants fro% burningcoal1oil1gas in energy generation etc/!er%s* )iruses and other undesirable )apour1gas concentrations are easily dispersed away fro% naturally )entilatedbuildings/

Naturally )entilated buildings offer a greater )ariation of indoor cli%atic conditions than air-conditioned buildings andpeople are liely to be healthier in naturally )entilated buildings/

#ir conditioning has its role due to building li%itations and constraints* particularly noise and e.ceptionally highhu%idity and dense indoor population/

In "ong ong* it usually lea)es %ore chance for designing natural )entilation in residential and institutional buildingsthan co%%ercial buildings/

2.3 Ther$al (o$fort - solar and natural 'entilation effects=or buildings o)erheated in Su%%er at day ti%e* the wall is at hot te%peratures at night* e%itting infrared radiation&i/e/ heat' to occupants who would then feel unco%fortable/ ,ith the sa%e principle* the blac bitu%en asphalt on theroads absorbs solar energy and re-e%its substantial IR - heat to pedestrians/Roo%s facing South in ,inter are war%er at night ti%e and are %ore co%fortable because they are heated by thesun at day ti%e/ Roo%s ha)ing large windows opening to the sy are %ore co%fortable at night ti%e in Su%%er &andcold in ,inter if' due to radiant cooling on people by the sy which is colder than the roo%/ Roo%s with sa%e windowareas facing other buildings &i/e/ not the sy' under the sa%e conditions &i/e/ naturally )entilated* with or without fans'are less co%fortable in Su%%er &and they are war%er in ,inter' because other buildings are at high te%peraturesthan the sy/

Ther%al co%fort is principally go)erned by radiant heat e.change* te%perature1)elocity and %oisture content of air

around us &i/e/ con)ecti)e effect'* and our body nature1acti)ities1health condition1clothing/

.2.) Design for natural 'entilation and Ther$al (o$fortNatural )entilation carries away heat* %oisture and odours1)apours1gases fro% the building* and pro)ides us with co%fort/"owe)er the inflow and outf low of air )ia buildings ha)e to be designed and controlled properly/ ist below are so%ereco%%endations:-3/ #lways* the larger the openings* the better/

F/ The openings to be pro)ided with ad+ustable co)ers1windows so that the openings can be ad+usted fro% ?@ to 3??@open* and the panels1windows to be ad+ustable in its angles when opening up* to opti%ise air in1out flow/

4/ In %ost locations in "ong ong* the locality of the building dictates the wind %agnitude and direction* the generalpre)ailing wind direction is not that i%portant/

A/ ,ind blowing on buildings create air pressures &positi)e and negati)e' on )arious building surfaces/ The wind then enters)ia positi)e pressure openings and lea)es the building )ia negati)e pressure openings/ The orientation for putting upopenings is not that i%portant* especially when ad+ustable panels1windows are pro)ided/

G/ Sylights are )ery desirable for night ti%e ther%al co%fort in houses to )ent heated1war% air that rises* and to let usradiate heat to the cold sy/ iewise windows open to the sy and other relati)ely cold surfaces such as the woods* the sea*would i%pro)e ther%al co%fort on the sa%e principle/

B/ et the sun heat the roo%s at day ti%e in ,inter and try to a)oid heating the building by other energy sources e.ceptwaste heat/

/ Use fans &a lot of )ariety - ceiling %ount* wall %ount* floor standing' to assist natural )entilation as needed/ #)oid airconditioning as far as possible/

H/ et the su% shine on the building &i/e/ walls1windows1roof' as desirable and to shade it off if not desirable/