Category Archives: BACKGROUND

Comparison ofenvironment performances provided by different daylighting systems for a sample environment

As an example ofapplication ofexperimental researches carried out by means ofscale models under artificial sky and sun, a specific case-study, concerning the assessment of environmental performances ofsimple shading devices, is presented. Tested shades were conceived and designed to be applied to educational buildings located in Turin. To analyse daylighting conditions inside high-school classrooms, a scale model was achieved so as to reproduce a sample classroom, representative oftypical real environments with regard to sizes, exposure, optical and chromatic internal surface properties and daylighting system typologies (unilateral side-lighting through vertical windows). For artificial sky and sun experimental activities purpose, the achieved model was 1:10 scale, featuring (figure 2):

Figura 2 — Scale model reproducing a sample classroom

sizes: reproduced classroom is 9 m long, 6 m wide and 3 m height, determined according architectural design handbook. These sizes are representative of typical real classrooms

• 2 windows in the south wall, each of them 3 m wide and 2 m height, sill being 0.9 m from floor level; the openings have a clear 6 mm glass and a grey frame similar to the one characterising some real classrooms

• internal surface colours and luminous reflectance values (rl): the ceiling is white painted (n = 0.72), walls have a lower part light blue painted (rl = 0.48) and an upper part with an ivory-coloured finish (rl = 0.61), while the floor is made of red brick (rl = 0.33)

• internal surface optical properties: all materials were assumed as Lambert diffusers. Among all possible solutions, shading devices chosen forthe south-oriented glazed wall consisted of both external and internal screens. Tested configurations are described in table 1. In particular, the performance ofa simple overhang was compared to the one of otherfixed screens (like external light-shelf, internal light-shelf, external-internal light-shelf and horizontal fins). The goal of improving daylight penetration in the rear part of unilateral side-lighted classroom was one ofthe criteria used to define the tested configurations. For this reason, the upper part of internal light shelves, different finishing were tested (matt, semispecular and specular). The same was applied to one of the horizontal fin (finished in both a matt and a semispecular material).

Screens’ size and position were determined in order to assure a comparable shading effect. Forthis reason, assumed configuration were characterised calculating the Shading

Factor value24 (SF) and the final geometry was set so as to have similar SF values (table 1 and figure 3) and an efficient shading effect with respect to Sun’s position during the year. The SF values were determined both for the summer time (referring to June, 21st) and for wintertime (referring to December, 21st), based on monthly average irradiance data measured for the town of Turin25.

As far as experimental activity is concerned, two sets of measurement were carried out for each shading configuration.

The former involved the use of the artificial sky, aimed at quantitatively assessing the illuminance and Daylight Factors values in correspondence of 16 points on the classroom’s work plane (positioned at a height of 0,8 m from the floor).

Measurements were repeated referring to different sky conditions and different daylight availability: both a CIE Clear Sky and a CIE Overcast Sky were assumed as reference standard sky conditions, while to take daylight variation during the year into account both a winter condition (identified in December, 21st, at noon) and a summer condition (June, 21st, at noon) were simulated.

The latter experimental set involved the use of the artificial sun, aimed at qualitatively evaluating the dynamic penetration ofthe Sun into the classroom fordifferent periods of the year and within a single day. The analysis was carried out for two “extreme” sun-light conditions: a winter day (December, 21st) and a summer day (June, 21st), respectively characterised by lowest and highest Sun’s elevation angles with respect to the annual solar dynamic behaviour. For both days, sun-light penetration was assessed at different hours: 9 a. m., noon and 4 p. m.

Simulation Results and Discussion

Figure 5 : Distances bettween buildings obtained with the iso-shadow method

First we observed the changes of solar volumes as a result of a single 6m high pole at various durations of solar exposure on the latitude 46.03N (Ljubljana, Slovenia). The1-3-5 hours duration (1 hour on the 21st of December, 3 hours on the 21st of March and 5 hours on the 21st of June) is the duration of solar exposure according to the legal requirement in Slovenia. Winter duration of solar exposure is only 1 hour, which is too short for any serious consideration of collecting solar energy. The incidence angle is 20°. The periods during spring and autumn are considerably longer (3 hours) compared to winter, but during that time the most of solar energy for heating can be used (at least 5 hours), so objective are long winter and spring/autumn solar exposures. The interest for summer solar exposure is oriented mostly on active solar features (solar collectors and PV), otherwise sun can present problem due to overheating. If we observe Figure 4: Distances bettween buildings obtained with the shape of the solar volumes for the sun-on-ground method the considered durations, we notice that summer solar envelope is almost “contained” within the spring one. With the solar volume method we have to combine two or more solar pyramids to satisfy the requirement (Fig. 2).The 1-3-5 hours shadows were taken as reference (they are the minimum requirement which protects the user from receiving no solar radiation at all).

The reference situation was changed in the way that the solar durations were increased in equal steps of 1 hour — from 1-3-5 hours to 2-4-6 hours. The 2-4-6 hours duration (2 hours on the 21st of December, 4 hours on the 21st of March and 6 hours on the 21st of June) represents a slightly improved basic situation. Due to that measure the solar envelope spreads its influence to the north for a minimum 1%, but the east and west influences double their size. As a consequence the maximum building density on the site decreases (when organizing the same size buildings) — but on the other hand the feasible building volume increases (Fig.2).

The 3-5-7 hours duration (3 hours on the 21st of December, 5 hours on the 21st of March and 7 hours on the 21st of June) (Fig.3) is a situation where winter and spring/autumn solar exposures are substantially prolonged. We can observe a change in the solar envelope pattern. The spring and summer solar volumes are contained within the winter volume.

The solar envelope influence increases toward north for 10% and towards east and west for a factor of 3.3 comparing to the reference situation 1-3-5 hours. Compared to the iso­shadows method the site size is much larger. This is a model for further investigation.

The 4-6-8 hours duration (4 hours on the 21st of December,

6 hours on the 21st of March and 8 hours on the 21st of June)

(Fig.3) is the maximum duration that can be achieved in the given circumstances. The winter elevation angle in this model is 16° (close to the 15° which are recommended in the literature).

As a consequence the summer azimuth angle is almost 90° declined from the direction South and spring azimuth is 56 declained from South. The summer and spring/autumn azimuths during early and late hours are too large to gain any reasonable benefit from solar incidence. The adjustments of summer and spring/autumn solar exposures could be made in the sense of diminishing the duration time.

Figure 6: distances between buildings obtained with the solar envelope methodfor the 2-4-6 hours duration (floor plan)

Solar volume method works well only for longer exposures, which contain the year-round shadowing in the winter solar volume — then we can say the volume is easy to understand and design. When the spring and summer envelopes »stick out« of the winter envelope we have two possibilities: combine several solar volumes or diminish the spring and summer solar exposures. One of the possible approaches would be to increase the winter and the spring/autumn durations of solar exposure and keep the summer duration at 5 hours (summer overheating of passive solar features) The 5 hour summer solar exposure would be contained in the adjusted 2-4-5 hours variant, the combination of the 2-4-6 hours variation and the 1-3-5 hours variation.

The solar volume method was compared to the sun-on ground and the iso-shadow method. The comparission was carried out on the simulaton model described previously in the text. Shadows calculated with the sun-on-ground method have almost rectangular shape (Fig.4). We can notice a distinctive longitudinal shape of the shadows running north, the east and west shadows are much shorter than the north ones. Laterally we can put the buildings very close together.

When we observe the results of the simulations obtained with the iso­shadow method we see that the shapes of the shadows are more complex and more evenly arranged around the building than in the previous method. It is evident that shadows over a long period of time were taken into consideration.

The shadows at the east and west side of the building have more influence (the consequence of the Figure 7: Distances between buildings obtained with

morning and afternoon sun, when the solar envelope method for the 3-5-7 hours solar

the incidence angles are low) duration (floor plan)

(Fig. 5). We can see on the picture that

the buildings have longer southern as well as east and west solar exposures during the year.

The distances between the buildings obtained with the solar volume method depend on the solar exposure duration. The results of the reference 1-3-5 hours duration resemble
the results of the sun-on-ground metho (Fig.6). With the increase of the solar exposure duration, the results become similar to the iso-shadow method, where we can certaily say, that 80% of insulation during the year will be available on the building envelope (Fig.8).

The results of the calculations show that the area of the shadowing is larger when calculated with the iso-shadow and the solar volume method. Figure 8: Distances between buildings obtained with

The shadowed area is more the solar envelope method for the 4-6-8 hours solar

evenly disposed around the duration (floor plan)

building than in the sun-on-ground method, where the shadows have a distinct north-south axes. Large shadows appear at the east and west sides of the buildings calculated with the iso-shadow and solar volume method. The lateral distances between the buildings have to be larger when defined with those methods, too. The shadow length and shape toward north are similar if calculated with all the methods.

THE CASE-STUDY: THE CFD MODEL

The analysed system is a typical stairwell of an in-line multifamily building divided into five storeys and with two dwellings per floor (see figures 1,2).

Fig.2: Plan view and main section of the stairwell

The main components of the ventilation system for each apartment are:

• wind-sheltered inlets located near windows or heating devices (for example, a grille mounted into an external wall or windowsill, equipped with adjustable deflectors);

• air-transfer device (for example, grilles mounted into the internal doors);

• operable louvers mounted at the top of the entrance unit;

• semi-automatic control system (each occupant can manually adjust the air-inlets of some or all the rooms to suit personal requirements).

The natural ventilation system has been designed in order to extract the exhausted air from each apartment and each unit is sealed off from the others. These are important characteristics of the ventilation system in order to avoid a short-circuit and guarantee adequate indoor air quality (IAQ) in each unit.

The system was verified in stationary winter climatic conditions (the hypothesised external temperature is 0°, a typical design value in a temperate climate), all dwellings are heated at 20 °C and the stairwell is unconditioned.

Conductive loss from interiors warms air in the stairwell, causing it to rise toward the roof. This warmed air is extracted at the top of the stairwell and, consequently, fresh air is supplied to each dwelling. The major driving forces causing air movement are the above illustrated mechanism and the stack effect; the wind effects were been ignored. The behaviour of this natural ventilation system is mainly related to the heating needs of buildings; so, this mechanism may be more affordable and continuous than wind-induced ventilation, especially in urbanized areas.

The model used in CFD simulations was simplified in order to optimise the computational time. The pressure losses in the apartment path were collapsed into a single resistance. Therefore, only the stairwell was modelled. The stairwell geometry was simplified and reduced to the essential components (flights of stairs, landings, steps). The openings were modelled as simple resistance or as simple sloping planes. The walls were 30 cm thick and simplified as a single layer. A three-dimensional view of the geometric model is presented in fig. 3.

Concerning the temperature boundary conditions, the external air temperature was set at 0°C near the external surfaces of external walls and ceiling of the stairwell; the internal air temperature (20°C) was considered near the internal surfaces of internal walls (dwellings all heated).

Fig. 3: CFD computational model and temperature boundary conditions.

The design process follows an evolutionary approach, by single or small changes to the geometry and boundary conditions [4].

The locations, the sizes and the pressure losses of openings were modified in order to design and/or verify the behaviour of the natural ventilation system. This data is specified in the subsequent chapter.

Regenerative Energy

11

Pfarrami

parish office

Biasgang

Gememdenegel

□lazed corridor parish wing

Pfarrhaus

wcaraqc

The heating and electricity demand of the complete complex were reduced by integrated planning decisions to an extremely low energy level, so that the demand could be met completely and economically by regenerative sources of energy. Two-thirds of the heating energy is covered with free environmental energy by passive use of solar energy, facade — integrated collectors, ventilation with heat recovery, and an earth-to-air heat exchanger, which can also cool the inlet air in summer. The remaining third of the heating energy is supplied by a boiler fuelled with wood pellets. A photovoltaic array on the church roof provides the electricity needed.

Zuluft

Mb lift

Fassadenkollektor Kombispeicher Luftungsaniage/

Holzpellet- Luftkollektoren. Regenw.

E’dkanai

Warn etauschei

esse

Wendeiameiien zisterne

100m

facade collector combined tank ventilation system/ wood-pellet air-heating coll, rainwater cistern

heat exchanger

boiler

rotatable slats

underground

duct 100m

exhaust

Facade collectors on the vicarage

Air-heating collectors on the church

Cross-section indicating energy systems

Principles and elements of natural ventilation

The principles of natural ventilation in buildings are relatively few and straightforward, relying on wind, thermal buoyancy, or both as driving forces. There is, however, a whole range of subtle and sophisticated ways to take advantage of the natural driving forces to promote the ventilation principles. This is exemplified in a number of both new and old buildings that utilise natural driving forces for ventilation.

Figure 1 Wind and thermal buoyancy, here illustrated with the wind blowing in a tree (left) and a glider ascending attributable to thermal buoyancy (right), are the two natural “engines” that can be utilised to drive air in, through and out of buildings.

The utilisation of natural ventilation in modern buildings is almost without exception done in conjunction with a mechanical driving force that assist the natural forces in periods when they do not suffice. The combination of natural and mechanical driving forces is most commonly referred to as hybrid1 or mixed mode2 ventilation in the literature. We have, however, decided to use the term natural ventilation in this paper, even if auxiliary fans are installed in the buildings we deal with. The reason for this is that our focus is on the "natural part” of the ventilation system, and the consequences and possibilities this part has for the architecture.

We use three essential aspects of natural ventilation to describe and classify various concepts. The first aspect is the natural force utilised to drive the ventilation. The driving force can be wind, buoyancy or a combination of both (Figure 1). The second aspect is the ventilation principle used to exploit the natural driving forces to ventilate a space. This can be done by single-sided ventilation, cross ventilation, or stack ventilation (Figure 2).

Figure 2 Sketches illustrating the three ventilation principles, from left to right; single-sided ventilation, cross-ventilation and stack ventilation. As a rule of thumb, single sided ventilation is effective to a depth of about 2 — 2.5 times the floor to ceiling height, cross ventilation is effective up to 5 times the floor to ceiling height and stack ventilation is effective across a width of 5 times the floor to ceiling height from the inlet to where the air is exhausted3.

The third aspect is the characteristic ventilation element used to realise and/or enhance the natural ventilation principles. These elements are characteristic for natural ventilation, and distinguish natural ventilation concepts from other ventilation concepts. However, natural ventilation can be realised without the use of dedicated ventilation elements. The building itself then doubles as a ventilation element. With such a building integrated element we understand that the building as a result of its design is capable of harnessing the natural

driving forces and of directing the ventilation air through its spaces without the need for dedicated ventilation elements. In this sense, a building integrated ventilation element is really not an element, but rather the absence of one. As the "ventilation system” and the occupants share the same spaces (rooms, corridors, stairwells et cetera), and windows and doors are utilised as part of the air-paths as well, the most characteristic feature of a building integrated element is that the building appears not to have a ventilation system at all. The main advantage with a building integrated element is that the ventilation system represents no additional use of space in the building. Ductworks, ventilation plants, and related components are avoided. The B&O Headquarters building is a good example of this approach.

Characteristic element

Ventilation principle

Supply or exhaust

Wind scoop

Cross and stack

Supply

Wind tower

Cross and stack

Extract

Chimney

Cross and stack

Extract

Double facade

Cross, stack and single-sided

Supply and extract

Atrium

Cross, stack and single-sided

Supply and extract

Ventilation chamber

Cross and stack

Supply and extract

Embedded duct

Cross and stack

Supply

Ventilation opening in the facade

Cross, stack and single-sided

Supply and extract

Table 1 The relation between characteristic ventilation elements and ventilation principles. The table also shows whether the individual element is used in the extract or in the supply end of the air-path. Some characteristic elements can be used both as extract and supply.

Most naturally ventilated buildings do, however, make use of dedicated ventilation elements to harness the natural driving forces and to support the airflow through the building. An overview over the various elements, together with the ventilation principle the various elements is most likely to be associated with, is provided in Tablel.

In addition to the principles and elements above, the nature of the supply and exhaust paths is crucial to the architectural consequences and possibilities associated with a natural ventilation concept. With supply and exhaust paths we understand the air path the ventilation air travels between the outside and the occupied spaces inside a building, i. e. not the airflow path within the occupied zones. The supply and exhaust paths can be divided into two categories: local and central.

A central supply path means that one or several occupied zones are serviced by the same path. The ventilation air can be given different treatments along this path. It can be filtered, heated and cooled, and fans can be installed to surmount pressure drops in the airflow path. Thus, one single filter unit, one single heat exchanger, and one single fan can service the entire supply airflow. A central exhaust path means that used air from one or several occupied zones is collected and exhausted at the same point. When both supply and exhaust paths are central, heat recovery is easier to implement. An embedded duct and an atrium are examples of central supply paths. A staircase that serves as a stack is a central exhaust path.

As opposed to central supply and exhaust paths, local supply and exhaust paths have no distribution system associated with them. The air is taken into and exhausted out of an occupied space directly through openings in the building envelope. Openable windows and hatches in the fagade are examples of local supply and exhaust paths.

Results

The luminous environmental performances of tested shading devices were assessed by means of different quantitative and qualitative information elaborated from the data collected during the diffused and direct light simulations.

As far as diffused component of daylight is concerned, average Daylight Factor (DFav), average illuminances (Eav), uniformity of illuminance distribution U (determined as DFmin/DFav and Emin/Eav) and profiles over a cross section of the horizontal plane were calculated.

Obtained results are shown in tables 2, 3, 4 and figures 4, 5.

The following trends can be emphasised from result analysis:

— the average Daylight Factor measured for the CIE Overcast Sky condition is over the minimum value recommended by the Italian Standards for classrooms26 (DFav> 3%) only when the internal light shelves are used. All the other devices ensure a DFav within 2,45% and 2,96%, with a better performance for the horizontal fins and a worse for the overhang and the external+internal light-shelves;

— in clearsky conditions, the highest average illuminances are achieved with the internal light shelves, intermediate and similarvalues with the overhang and the horizontal fins and lowervalues respectivelywith the external light shelfand the external+internal light shelves;

— the uniformity of daylight distribution over the horizontal plane is quite similar for the external light shelf, the external+internal light shelves and the horizontal fins, while it is reduced if the overhang or the internal light shelf are used;

— the light penetration towards the rear part of the classroom and the uniformity of distribution along the cross section (assessed for each point along the section in terms of Daylight Factoror illuminance relative difference with respect to the overhang — tables 2,3,4 — and by observing the graphical representation offigures 4, 5) are higher for the horizontal fins and the external light shelf and respectively lower for the external+internal light shelves, the overhang and the internal light shelves.

code

description

Fs 0)

summer, winter, June,21st Dec.,21st

1

0

overhang — matt diffusing

reflectance = 0,7 — depth = 0,6 m

55

88

2

ELS

external light-shelf — matt diffusing

reflectance = 0,7 — positioned 0,55 m awayfrom window’s lintel — depth = 0,7 m

55

87

3

ILS1

internal light-shelf — matt diffusing

reflectance = 0,7 — positioned 0,55 m awayfrom window’s lintel — depth = 0,55 m

not

applicable

not

applicable

4

ILS2

internal light-shelf — semispecular

reflectance = 0,9 — positioned 0,55 m away from window’s lintel — depth = 0,55 m

not

applicable

not

applicable

5

ILS3

internal light-shelf — specular

reflectance = 0,9 — positioned 0,55 m awayfrom window’s lintel — depth = 0,55 m

not

applicable

not

applicable

6

E+ILS1

external light-shelf+ matt internal light-shelf

see cases ELS and ILS1

55

87

7

E+ILS2

external light-shelf+ semispecularinternal light-shelf

see cases ELS and ILS2

55

87

8

E+ILS3

external light-shelf+ specular internal light-shelf

see cases ELS and ILS3

55

87

9

HF1

horizontal fins — matt diffusing

reflectance = 0,7 — fins’ spacing = 0,67 m — fins’ depth = 0,2 m

53

88

10

HF3

horizontal fins — matt diffusing + 1 semispecular

reflectance = 0,7 / 0,9 — fins’ spacing = 0,67 m — fins’ depth = 0,2 m

53

88

Table 1 — Description of analysed shading system configurations

<1) Fs = Shading Factor, defined as24:

Fs, b • lb+Fs, d • Id + [a lb + Id + la

Fs, b = sun-light fraction of the window in presence of direct radiation [-]

Fd, b = skylight fraction of the window in presence of direct radiation [-]

lb, ld, la = direct irradiance, diffuse irradiance and irradiance reflected from the albedo incident onto the glazed surface [W/m2]

matt / semispecular / specular

cross section

—ft—- ft—- ft—- ft —

cross section

—&—- #—- #—- —

cross section

—&—- Э*—- #—- —

overhang

external light-shelf

internal light-shelf

^iatt / semispecular / specular

^matt / semispecular

cross section

cross section

|—fc———- *——— «———

external-internal light-shelf

horizontal fins

Figure 3 — Geometry and position ofanalysed shading systems

SHAPE * MERGEFORMAT

Table 2 — Average Daylight Factor, uniformity of distribution overthe horizontal plane and

CIE Overcast Sky

О

CO

_l

Ш

CO

CM

CO

-J

CO

CO

J

E+ILS1

E+ILS2

E+ILS3

Li.

X

CO

Li.

X

DFav [%]

2,54

2,68

3,46

3,51

3,56

2,45

2,52

2,54

2,86

2,96

U = OFmin/DF, av

0,33

0,40

0,30

0,31

0,31

0,38

0,39

0,38

0,39

0,38

distance from window fm]

DF relative difference (referred to the overhang) f%]<v

0,75

0,00

0,02

51,47

53,04

53,19

-3,39

-1,67

-1,34

2,11

4,39

2,25

0,00

16,78

29,29

32,36

34,51

4,26

7,30

9,82

28,89

32,81

3,75

0,00

6,44

9,06

12,55

15,20

-11,74

-8,46

-5,73

17,56

20,26

5,25

0,00

27,76

21,47

23,75

26,84

10,54

12,72

15,64

29,98

30,82

Table 3 — Average Illuminance, uniformity of distribution over the horizontal plane and relative difference of daylight quantity over the cross section (CIE clear sky — Dec. 21st).

CIE Clear Sky

December, 21st — noon

О

CO

_l

Ш

CO

J

CM

CO

J

CO

CO

J

E+ILS1

E+ILS2

E+ILS3

Li.

X

CO

Li.

X

Eav [lux]

4089

3883

4564

4625

4669

3535

3704

3752

3932

4023

U = E

0,54

0,62

0,54

0,52

0,53

0,59

0,57

0,58

0,60

0,59

distance from window fm]

E relative difference (referred to the overhang )f%](1)

0,75

0,00

-11,06

13,36

14,89

15,09

-11,96

-10,18

-9,99

-12,90

-10,17

2,25

0,00

-3,99

13,37

15,76

17,23

-10,18

-8,04

-6,35

1,58

3,81

3,75

0,00

-8,22

1,96

3,71

5,57

-19,30

-17,53

-15,57

-3,02

-2,88

5,25

0,00

9,64

10,19

9,96

12,06

-4,78

-5,04

-2,94

7,84

8,26

Table 4 — Average Illuminance, uniformity of distribution over the horizontal plane and ^^^/edifference_^<daylight^ja^ity_over_t^3_cross_section(CIE_clear_sky_-_Jun^22st).i

CIE Clear Sky

June, 21st — noon

О

CO

_l

Ш

CO

J

CM

CO

J

CO

CO

J

E+ILS1

E+ILS2

E+ILS3

Li.

X

CO

Li.

X

Eav [lux]

1682

1637

2142

2174

2203

1472

1552

1571

1715

1748

U = Emin/Eav

0,43

0,50

0,38

0,39

0,39

0,49

0,48

0,48

0,48

0,48

distance from window fm]

E relative difference (referred to the overhang) f%](v

0,75

0,00

-9,91

40,35

41,53

42,44

-14,08

-12,19

-11,78

-6,46

-4,62

2,25

0,00

2,79

17,50

20,07

21,73

-8,06

-3,92

-2,10

10,48

13,92

3,75

0,00

-2,31

4,47

6,07

8,06

-13,90

-12,01

-10,06

4,16

6,06

5,25

0,00

11,90

12,08

12,85

14,87

-1,22

-0,05

1,77

12,34

14,70

™ Daylight Factor or illuminance relative difference with respect to the overhang are calculated through the formula: (DFi — DF0)/DF0; (Ei-E0)/E0

DFi; Ei = Daylight Factor; illuminance measured for each shading device DF0 ; E0 = Daylight Factor; illuminance measured with the overhang.

Figure 4 — Daylight Factor measured along the cross section (CIE Overcast Sky condition)

CIE Clear Sky (Dec. 21st — noon)

distance from the window [m]

Figure 5 — Illuminance measured along the cross section (CIE Clear Sky condition)

Even if similar trends of performance can be observed for the different sky conditions and period of the year, different absolute values emerge due to the different luminance distribution of the sky vault (tables 2,3,4 and figures 4,5).

As far as the direct component of daylight is concerned, digital pictures taken inside the model to analyse the visual perception ofthe produced luminous environment are the collected results. A sample of sun-light penetration produced by the different shading devices during the 21st of December at different hours of the day is presented in figure 6. With the exception of internal light shelves the tested shading devices provide an effective protection from direct sun light in summer period (June, 21st) (no direct sun-light observed inside the model).

The use of specular or semispecular finishing for the upper part of internal light shelves and horizontal fins seems to produce a general increase of illuminance on the horizontal plane inside the model (Tables 2,3,4). Furthermore they differently contribute to increase daylight penetration in the centre and rear part of the model, as shown in figure 8.

ELS

ILS2

HF3

Figure 6 — Example of direct sun-light penetration

Figure 7 — Effect ofdifferent finishing on ceiling light distribution

The effect of different finishing is also perceptible in the images taken during sun-light simulations (figure 7).