Incorporation Of Daylight In Buildings Engineering Essay

Daylight is ever chose interior infinite in all edifice types particularly in residential 1s. On one manus, it is a cost-free natural visible radiation and its efficiency may cut down the cost of runing electric visible radiations. On the other manus, unreal visible radiations need power to bring forth electricity, they will do emanations of C dioxide and other pollutions at the same clip. Besides, daytime besides has some more economical benefits indirectly. Constructing residents have biological demands of daytime ( Lam 1997 ) . Leslie ( 2006 ) points out that “ These demands include orientation, physical security, definition of personal district, relaxation of the organic structure and head, accommodation of the biological clock, and contact with nature and sunshine. ” Although daytime could supply indirect and personal advantages to residential and non-residential residents, quantified benefits are merely available for non-residential constructions presents.

Interior and exterior factors determine the quality and measure of daytime a edifice could acquire. In Hong Kong, high-rise edifices are close to each other for limited land usage, hence daylight designs ever depend on external factors.

When confronting big adjacent edifices in the period of daylight, the daytime degrees in kitchen and living/dining were less than the standard care illumination. D.H.W. ( 2006 ) indicates that the daytime degrees will be affected chiefly by neighbouring edifices, therefore natural visible radiation has strong relationship with externally reflected constituents. One of the efficient solutions is to utilize electric lighting in these residential flats.


Daylight is ever regarded as one of the best light beginning for colour rendition which could fit human ocular response rather closely. In footings of psychological science, daytime has a evidently positive impact on people ‘s sense of cheeriness and brightness.

The measure of daytime come ining a edifice chiefly depends on window gaps. When they admit appropriate daytime for interior infinite, they non merely offer people comfort ocular contact with outside word, but besides provide a attractive and delighting atmosphere. Therefore, people do want better natural visible radiation in their life infinite.

Situation in HONG KONG

Hong Kong is regarded as one of the most dumbly populated metropoliss in the universe. In order to fulfill the turning population, there are many challenges in lodging demands. When the land resources are more and more finite, most of residential blocks are built near to each to other, therefore sky obstructors is terrible. ( D.H.W. Li, S.M. Lo, J.C. Lam, R.K.K. Yuen, Daylighting public presentation in residential edifices, Architectural Science Review 42 ( 3 ) ( 1999 ) 213-219. )

The quality and measure of interior infinite daytime is restrained, particularly in lower floor flats. They even have to trust on electric visible radiations during daytime period. ( D.H.W. Li, J.C. Lam, Daylighting in residential territories undergoing urban reclamation, International Journal of Ambient Energy 22 ( 3 ) ( 2001 ) 115-122. ) Natural visible radiation which indoor infinite could acquire non merely from daylight straight from the sky. It depends on both exterior and interior factors. External parts include: contemplation of the land and opposite edifice frontages. ( A. Tsangrassoulis, M. Santamouris, Numerical appraisal of street canons

albedo consisting of perpendicular coated glassy frontages, Energy and Buildings 35 ( 5 ) ( 2003 ) 527-531. ) ( A. Tsangrassoulis, M. Santamouris, V. Geros, M. Wilson, D. Asimakopoulos, A method to look into the potency of south-oriented perpendicular surfaces for reflecting daytime onto oppositely confronting perpendicular surfaces under cheery conditions, Solar Energy 66 ( 6 ) ( 1999 ) 439-446. ) Internal 1s are: the size and window places, the deepness and form of interior infinite and the colourss of suites ‘ surface. ( J.C. Lam, A study of bing residential edifices and envelope designs in Hong Kong, International Journal for Housing Science and Its Applications 18 ( 1994 ) 112-124. ) Actually, the interactions of different design schemes will impact daylight public presentation earnestly. It is complex to understand these rather good. ( D.H.W. Li, J.C. Lam, S.L. Wong, Daylighting and its deductions to Overall Thermal Transfer Value ( OTTV ) findings, Energy-The International Journal 27 ( 11 ) ( 2002 ) 991-1008. )

Daylight factor ( DF ) which is expressed as a per centum is used to measure the public presentation of daytime of a edifice. It is defined as the ratio of interior light to the light at the same time available on a horizontal plane in the status of an unobstructed cloudiness sky. ( G.R. Hopkinson, P. Petherbridge, J. Longmore, Daylighting, Heinemann, London, 1966. ) In order to cipher, a DF is frequently divided into three constituents: the sky constituent ( SC ) , the externally reflected constituent ( ERC ) and the internally reflected constituent ( IRC ) . The likely daytime illumination in residential edifices ever determined by five cardinal edifice parametric quantities, including constructing country and orientations, window country, glass type, shadowing and external obstructor.

Window countries

The handiness of familial daytime chiefly depends on window country when the glazing type is given. In Hong Kong, the window country and openable Windowss should be more than one-tenth and one-sixteenth of the room floor country, required by local Building Regulation ( Hong Kong Government, Building ( be aftering ) Regulation. Law of Hong Kong Chapter 123 Subsidiary Legislation, Law Ordinance, Hong Kong, 1990 ) . Defined as the ratio of the entire country of Windowss to the overall gross outside wall country ( including Windowss ) , window-to-wall ratio ( WWR ) is considered to stand for window country during the edifice envelope designs. WWRs in Hong Kong are ever between 25 % and 30 % . However, edifices in high denseness countries which might be rather close to each other and whose Windowss are on the shorter frontages normally have low WWRs. Relatively, big luxury flats on higher floors in lower denseness residential territories appear to hold WWRs more than 35 % .

Harmonizing to salable floor country, residential units are split into five classed by the Rating and Valuation Department in Hong Kong. They are Classifying A ( less than 40 M2 ) , Class B ( 40-69.9 M2 ) , Class C ( 70-99.9 M2 ) , Class D ( 100-159 M2 ) and Class E ( 160 M2 and above ) . Class A and Class B which less than 70m2 are the most popular residential unites of high-rise edifices with 10s to thirty narratives. Basically, there are four to eight flats per floor in high-rise residential edifices, and as a symmetrical layout, organisations of indoor infinite has small difference in orientation. Furthermore, for finite land resource and high denseness of population, edifices have to be badly close to each other and small infinite left to steer.

The multi-story flat block used for survey has six units each floor. ( Fig. 1 ) It could demo the typical domestic unit including three sleeping rooms, a living/dining room and a assorted country ( kitchen and two bathrooms ) . The purpose is obtaining information of internal daytime public presentation in Hong Kong therefore the typical unit with life room, sleeping rooms and kitchen is suited for the analysis. It is Class B and entire floor country is 68m2. The parametric quantities for daylighting calculations are shown in table 1.

As “ green ” and “ sustainable ” residential edifices, they should be non merely energy efficient but besides natural and more comfy for residents.

In Hong Kong, residential edifices should be built to a secret plan ratio of more than 10 which is defined as entire functional floor infinite divides site country, and the site coverage should be more than 50 % . As a consequence, 40-80 narratives edifices are normally built rather closely and the denseness of site might be every bit high as 4000 individual per hectare. ( Figure 1 )

The Building Regulation govern both light and airing of edifices in Hong Kong. However, the Torahs based on an aged UK theoretical account are rather old. Harmonizing to the construct of perpendicular angel demands of 71.5A° presents, the distance between edifice blocks is minimal, which has proved to be non appropriate. Furthermore, it courage bad designs and disregard good 1s. ( Figure 2 ) At this minute, a new regulative design scheme is required.

Based on Vertical Daylight Factor on the surface of window, a minimal daylight public presentation is fixed. A unsophisticated design scheme based on ‘Unobstructed Vision Area ‘ ( UVA ) was worked outi??using theoretical mold, on-site measurings and computational simulation harmonizing to both existent and conjectural instances. The Unobstructed Vision Area Method ( UVA ) has strong relationship with the Vertical Daylight Factor ( VDF ) of a edifice frontage. At the beginning of design period, this 2D method is really convenient to utilize. As there is no large alteration in its variables, the UVA construct could be used in other metropoliss with utmost denseness.


The survey indicates that the lower floor has really hapless daylight public presentation in high-rise residential blocks. VDF is approximately 6 % to 8 % . While standard daylight factor of habitable suites should be about 0.2 % , kitchens in the place of the terminal of a deep re-entrant about has no visible radiation at all, the figure of which is rather close to 0.0 % . ( Figure 3 )

Window is the cardinal beginning of most concern, but there are some defects in window design which affect the daytime interior infinite straight: 1 ) Windowss located excessively deep in chief facade ; 2 ) Windowss confronting narrow streets without adequate infinite ; 3 ) Windowss in little spreads of these four cruciform edifice blocks ; 4 ) Windowss put in some tight infinite such as meshing Rectangular Horizontal Plane ( RHP ) ; 5 ) Windowss positioned at the corner of suites which are non proper to obtain equal illuminate.

User Requirement

What is the fulfilling daylight public presentation in high-rise homes people would wish to accept in Hong Kong presents?

There are many paperss stipulating daylight public presentation, and some of these criterions are chiefly based on experimental informations entering from human responses. However, non many edifices have good daytime public presentation in high-density urban country. Harmonizing to assorted socio-cultural and climate factors, residents may accept the hapless daylight public presentation in some hypothesis. Therefore, which is the acceptable criterion daytime public presentation? In this survey, 12 major high denseness homes are chose for user study and computational simulation. ( Figure 4 )

About 6000 Windowss of these 12 homes got computing machine simulation consequences of daylight public presentation. ( Figure 5 ) With the aid of user surveyed, computing machine consequences of daylight handiness of the Windowss was identified and recorded into the study signifiers. Finally, users ‘ satisfaction rates were computed from the daylight public presentation informations and the associated user responses of each room.

Harmonizing to the responses of residents in Hong Kong, it is indicated that the minimal satisfying degrees of daylight public presentation are really low. Most of people expressed about the same attitude to daylight in the study. Peoples will get down to mind and kick about daytime if daylight public presentation is perfectly low and sub-standard. Therefore, it is the fact through the minimal acceptable criterion is low. It is possible to graduate a criterion of the exchanging behaviour based on available informations.

The graph shows the relationship between user satisfaction and simulated daylight public presentation. For life suites, the satisfaction rate is around 80 % when VDF is 10 % . Satisfaction rate rises with the increasing of the sum of available daytime, although the betterment is non obvious. In brief, it is difficult to derive 15 % VDF and 30 % VDF. If the degree of daylight public presentation goes down to 8 % , people ‘s satisfaction rate fails dramatically.

For sleeping rooms, evidently, people favor the higher daylight public presentation. When VDF is more than 20 % , the satisfaction rate is around 80 % . But when VDF drops to 10 % to 20 % , 70 % of users say the daylight public presentation is acceptable.

For kitchen, the minimal criterion of acceptable daylight public presentation is really low. Possibly it have the relationship with dwellers are used to the bing hapless daylight public presentation in residential edifice design. Even the VDF around 4 % , still 80 % dwellers express their satisfactory. In short, acceptance rate beads quickly, which indicate a threshold issues with low required criterion.

As a consequence, 80 % user satisfaction is used for set uping the criterion threshold ( Figure 6 ) . Populating room and sleeping room could be considered together as habitable suites in order to simplify the operation of research and their acceptable perpendicular Daylight Factor ( VDF ) should be more than 8 % , while the figure of kitchen should be at least 4 % .

In Hong Kong, there are three characters of high-rise residential edifices.

The tallness of most edifices are about 40 to 60 narratives high.

In order to supply natural airing, exterior envelope signifier of blocks are really complex with many reentrant countries.

Hong Kong is a high-density country, neighbouring edifices are rather to each other.

The cardinal point in design procedure is to maximise the potency of secret plan for increasing the Numberss of unites other than estate planning and flat layout, which are 2nd of import. There is no specific design for the public presentation of daytime into single flats or to common external countries. In brief, some flats suffer earnestly form solar radiation job, while some others could non acquire equal degree of natural visible radiation. Turning Numberss of people are cognizant better design information and pattern.

Background, Scope and Aims of Study

There is no uncertainty that acceptable interaction of sunshine and daylight a edifice could acquire demands careful design attending. Natural daytime to indoor infinite is necessary from an aesthetic point of view. However, the sunshine enters into a room of residential blocks with solar heat addition, which may increase chilling burden. Therefore, comfort conditions depend on natural airing in a room when the daytime public presentation is appropriate.

With cut downing the sunlight incursion, the daylight degree should be maximized in estate blocks, based on a pleasant internal visual aspect and cutting usage of unreal visible radiations. Actually, cut downing unreal illuming burden could diminish the sum of chilling burden and energy ingestion. Furthermore, daytime offer the ocular contact with the outside environment with a position of sky and human psychological demand.

In this survey, the balance between daytime and sunshine should be considered carefully. Therefore in order to maximise degree of daylight public presentation and minimise solar incursion of internal infinite, professional and specific design accomplishment is required for covering with the 3-dimensional geometry involved, even conflicts between constructing surface and site obstructor and shading job. Design scheme without carefully consideration could non be equal for the environment with high-density edifice but complex single edifice signifiers.

It is non surprising that applicable and practical design needs suited hypothesis.

Multiple edifices are really near to each other, therefore complex exterior obstructors are called for.

Self shading is necessary for typical complex edifice program.

Assorted overcast flip conditions

Solar and sunlight control measurings including: internal blinds, external sunglassess and tinted and mirrored glazing.

Daylight public presentation of complex edifice blocks depends on sufficient power of attacks in design, there are two of them:

Physical graduated table mold: for accurate appraisal, a graduated table edifice theoretical account should be put in an unreal sky or heliodon installation

Numeric simulation theoretical account: for developing a mathematical word picture of daylight public presentation, a numeral representation of the edifice geometry is in usage.

These two attacks are compared by the easiness of usage, quality and how deep of the consequences come-at-able. Consequences of the two mold attacks were distinguished by facets including: pertinence, capableness, the appraisal of solar incursion to external countries, solar incursion to internal infinites, daylight to internal infinites, and position of the sky.

The methods were based on a specific lodging development in Hong Kong: Tseung Kwan O Area 59. This residential edifice country is typical Hong Kong new lodging estate development. There are some 16, thirty-nine-storey Harmony-1 blocks on class and, on a dais, a commercial Centre and auto park in this country. As shown in Figures 1 and 2, they are illustration estate layout and typical floor program. Specific methods studied via an illustration of physical graduated table mold, in the status of an unreal sky and heliodon installation, utilizing advanced computing machine mold, ECOTECT and RADIANCE.


Physical Scale Modelling

Physical illuming mold ever gets consequences by two ways: puting a scale theoretical account to a existent clime or to a fake clime in an unreal sky environment. The former 1 could be more accurate but uneasy to command in vagaries of clime. By comparing, The latter could supply flexibleness and repeatability with equal unreal sky. Nowadays, the production of graduated table theoretical accounts is popular harmonizing to limited Numberss of such installations. Skylight is simulated by 640 leading lights under computing machine control, which could bring forth standard CIE sky status from cloudiness to unclutter.

Model graduated table is 1:500, which is big plenty to incorporate a mark block and most neighbours in the cardinal “ on the job volume ” of the 0.5_0.5_0.3 m high installation. Size is indispensable in physical mold. ( Mardaljevic J: Quantification of parallax mistakes in sky simulator domes for clear sky conditions. Lighting Res. Technol. 2002 ; 34 ( 4 ) : 313-332. ) That means the theoretical account could acquire accurate angels and positions every bit good as offer a possible uniform surrounding. These could easy acquire a whole twenty-four hours resulsts at any sample day of the month during a twelvemonth. It is convenient to acknowledge the overshadowing or somberness and the causes of them. A big figure of point of views and repeated heliodon trials are necessary for covering a full estate. These restrictions might be overcame by farther technique at present. The theoretical account need sensitive surfaces of the frontages and land for instantly record of daytime. As a consequence of a wet photographic procedure, it is non practical to utilize this attack considered as complex and clip consuming. Objectively, physical mold of this graduated table can non work out the jobs such as sunshine and daylight incursion into suites and the position from interior infinite. The single block was non large plenty and suites were non attempted. There are no optical or sensor investigations available to mensurate the theoretical account at this graduated table. A individual flat of 1:25 graduated table would be made individually, with a quarter-circle of it contained with installation. In this theoretical account, self-shading characteristics and internal measurings are all included, without consequence of the floor location or next edifices. Facade light on window indicates the an mean indoor light ( Peippo K, Lund PD, Vartiainen E: Multivariate optimisation of design tradeoffs for solar low energy edifices. Energy and Buildings 1999 ; 29 ( 2 ) :189-205. ) which can be measured by photoelectric cells integrated straight. Actually, it is hard to do the theoretical account graduated table, as the smallest photoelectric cell is merely about 15mm in diameter. A dependable measuring based on a research-grade integration photometer, harmonizing to the investigation can non supply a high end products in a comparatively high-intensity unreal sky. Sing these disadvantages of the graduated table theoretical account, it may be impossible to enter the light conditions or solar incursion in each unit individually. In brief, when the unreal sky and heliodon trials could supply a direct analysis of the sunshine or daytime cover the whole site, it is non so easy to acquire the same information of the person blocks because of the theoretical account graduated table.

Computer Modeling

Computer patterning method could supply both daytime and sunlight anticipation. The package bundles of daylight factor ( DF ) and shadow form computation have been used on simple built-form without adequate capableness to depict context. Presently, this bundle is available for the simulation of both the macro-scale and micro-scale. The former one is the overshadowing of edifices, and the latter is the light degrees in and single edifice.

In order to entree both sunshine and daylight public presentation in residential development, this survey used ECOTECT ( Marsh A: Integration public presentation patterning into the initial phases of design. ‘ ANZAScA Conference Proceedings, Hong Kong, 1996 ) as environmental package bundle and RADIANCE ( Ward G: Auxiliary Notes – Radiance Synthetic Lighting Simulation Application, Lawrence Berkeley Laboratories, 1994. ) as the simulation system for illuming theoretical account.

When imitating the sites of edifice illustrations and their milieus, these two light simulation systems could supply the geometric description of a scope of suites, every bit good as the walls and the Windowss of them. That means they could see both the self-shading and site obstructors. In theory these tools have no barriers in footings of graduated table of theoretical account, except the truth or handiness of input informations. In pattern, there still restriction including: the memory infinite for informations storage and computation, the length of clip required for complicated jobs. Fortunately, both RADIANCE and ECOTECT could pull off about any complex jobs non merely for single flats and their contexts but besides the geometric theoretical account of the edifice. Figure 5.

ECOTECT uses an synergistic system as the physical heliodon, which provides immediate appraisal of location and continuance of solar tailing. Comparing with the physical methods, it is easy to quantify the glooming countries with time-average ground-level light. Figure 6 This system could work out the impact of signifier and denseness jobs as a complex program. Positions of the sky into different Windowss could be rapidly recorded and compared, every bit long as the geometrical nature of the signifier put into this system.

RADIANCE is used for ciphering natural visible radiation degrees in different flats. Basically, computations depends on daylight factors ( DF ) , in the status of the CIE overcast flip status with 100 horizontal illumination. High-quality rendition facets are needed: variableness, quality and item. They are necessary though computation clip devouring. Figure 8 shows the computation of interior daylight public presentation every bit good as exterior values. ( The flat of twentieth floor will hold below 4.5 % for its half country, while 35th floor could hold bulk infinite daylight country. ) When utilizing the unreal visible radiations, it is hard to enter the consequence of daylight public presentation. However Hunt ( Hunt DRG: Predicting illuming usage – a behavioral attack. Lighting Research and Technology 1980 ; 12 ( 1 ) :7-14. ) and guidelines of Building Research Establishment ( Building Research Constitution: Digest 272: Light controls and daytime usage. BRE, Watford, UK, 1985. ) outline that there should be tend to exchange unreal visible radiations in the status of plenty daytime.

The daylight handiness of the lower floor is affected by the external frontages of next edifices. In other words, one of the most important design factor is the colour of external walls and characteristics. More suites could be bright via higher coefficient of reflection nearby surface Figure 9 shows the different visual aspects in the same level when increasing the coefficient of reflection of nearby surfaces from 0.45 to 0.8. As we can see from the consequences, there is a important addition, and the daylight public presentation is rather close to upper floors in the obscured sky status. In add-on, the upper floors get more daytime at the same clip.

Many methods are extremely sensitive to input values, they require strict proof before adopted to utilize. Their operation, premises and restrictions are required to be carefully checked in novel or utmost application. It is necessary to cross-check the consequences if the method is the lone one available technique in the research. Actually, RADIANCE is better used by an expert or experienced user for its character of complex and professional. Inappropriate informations and options could change consequences significantly, more attending should be paid in the instance of daylight simulations.


Green characteristics include some indispensable facets: balconies, communal sky gardens, gardens, dais gardens, awnings and reflectors and flying wall. When maximising the use of natural resources and renewable energy, it is better to integrate these edifice characteristics during design procedure. The advantages of utilizing more natural resources are the decrease of constructing energy ingestion in the facets of air-conditions and unreal visible radiations. Besides cut downing solar addition an indoor air temperature, awnings, reflectors and balconies can better the sum of natural daylight public presentation of interior infinite other than utilizing unreal visible radiations.


Traditionally, balcony uses the gallery construct in the position of clime. It has two chief maps by increasing the deepness of the facade: buffering interior infinite and cut downing the solar heat addition. The benefits of balcony are better solar shading and heightening natural airing. The balcony of the upper floor could be regarded as a deep slab to the window of lower floors ( Figure 2 ) like the map of awning. When this deep overhang provide larger country of glazing of internal infinite, it cut down the solar heat addition straight every bit good as acknowledging more sunlight and daylight reflected from other surface of nearby edifices.