Category Archives: BACKGROUND

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).

CONTEMPORARY VS TRADITIONAL VS SOLAR HOUSES

Dr. Petros A. Lapithis. Intercollege, P. O.Box 24005, 1700 Nicosia, Cyprus

Tel: +357 22351274, Fax: +357 22353682, E-mail: lapithis. p@intercollege. ac. cy,

http://www. intercol. ac. cy. www. lapithis. com

The aim of this research is to investigate the traditional and contemporary architecture in order to further improve design methodology in passive solar architecture, and presenting an example of an ideal energy efficient house that takes into account climate, comfort, passive solar systems and the history of architecture of Cyprus.

Thermal performance of traditional, contemporary and solar houses is discussed in relation to climate and in terms of the various aspects necessary for understanding such performances. These aspects include architectural design, constructional materials and methods, occupancy patterns and planning. Different architectural and constructional elements and techniques that were used in traditional houses are studied in relation to their use in passive design today and serve as fine examples of energy-saving architecture.

The following conclusions were made concerning thermal comfort in Cyprus1:

• An average of 19.5°C — 29°C is the proposed temperature, within the comfort zone limits of Cyprus

• An average of 20-75% is the proposed relative humidity, within the comfort zone limits of Cyprus.

Cypriot traditional houses have proved to be superiorly energy-efficient when compared to contemporary houses due to the thermal performance of both cases based on their architectural design. Comparative annual energy use was performed using computer simulation software Energy 10 resulting that the most energy efficient is the experimental solar house (121 kWh/m2) following the traditional (243 kWh/m2) and final the contemporary (368 kwh/m2).

Taking into account the general characteristics of the dry climate and the requirements it imposes on the house characteristics and the general characteristics and thermal performance of traditional and contemporary houses, it may be concluded that traditional houses in Cyprus meet the requirements imposed by the climate and that these houses are good enough thermally to perform well under the prevailing weather conditions. Because of Cyprus climate, passive solar architecture works to its full capacity. This means that, a passive solar house has 100% energy saving potential. This theory has not remained at its conceptual stage as the experimental solar house has demonstrated it in practice.

THE CASE-STUDY: THE NUMERICAL CFD SIMULATIONS

In the first stage, a very common configuration (both for new buildings and for existing ones) was hypothesised:

• stairwell door at base closed; operable hinged hopper type window mounted at the top of the main entrance (generally closed in winter);

• small operable hopper window at each half landing (partially open);

• stairwell door at roof closed; exhaust air device mounted above this door;

• full louvered opening at the roof level (wind sheltered);

• full louvered narrow openings above the entrance door of each flat (all openings are characterized by the same dimensions and pressure losses).

The CFD simulations highlight that (figures 4, 5):

• the neutral pressure level (NPL) is located near the mid-height of the building;

• air is extracted from the flats below the neutral plane and is supplied to the apartments above the neutral plane; this mechanism involves a different airflow rate on each floor and poor indoor air quality at the higher levels;

• cold air enters the stairwell from the windows at the half landing level causing thermal discomfort and thermal losses.

In the second step, the windows at the half landing levels were considered closed. The temperature in the stairwell is higher, but the main behaviour is the same as the first case (see fig 5, step 2).

SHAPE * MERGEFORMAT

Fig.5: Velocity and temperature fields of steps 1 and 2.

3

Speed

iTempeiature

Speed

(rn/s)

ШВ?1-

,n. V, ■

2.4385

■ за?:’.-;-

2.15756

■ 177778

: 8Э661

■ 15 5556

: 62567

Щ13 3333

1.35472

11 1111

1.03378

Mjf 8. S8E89

0.812834

^ 6.66667

0.54189

■ 4/4444

0.270945

■ 2.22222

0

Я Q.

Fig.6: Velocity and temperature fields of steps 3 and 4.

In the third step the window at roof level was oversized in order to move the neutral pressure level upward. The results shown in fig. 6 highlight that the air is extracted from all the dwellings. The air exhausted from dwellings rises in the stairwell flowing along two main patterns: the first flow path is helicoidal in shape (just below the flights of stairs and landings), the second one is a vertical path along the core of the stairwell. The velocities are low and the exhausted air seems not to interfere with the occupied zone.

The calculated flow rates (see table 1) range from 0.027 to 0.440 m3/s, that is about 0,33­5.28 ACH (dwelling net volume = 300 m3). The above values are evaluated in favourable conditions (minimum external temperature in winter), so the minimum air change rate may be not enough for ventilation purposes under higher external temperatures.

STEP 1

STEP 2

STEP 3

STEP 4

STEP 5

T ext = 0°C

T ext = 0°C

T ext = 0°C

T ext = 0°C

T ext = 8°C

Opening

H [m]

Q

[mA3/s]

P

[Pa]

Q

[mA3/s]

P

[Pa]

Q

[mA3/s]

P

[Pa]

Q

[mA3/s]

P

[Pa]

Q

[mA3/s]

P

[Pa]

flat 1st floor, sx grille 100 X 20 cm

5.60

Q1

0.289

-3.717

0.396

-6.988

0.437

-8.507

0.177

-9.513

0.141

-5.986

flat 1st floor, dx grille 100 X 20 cm

5.60

Q’1

0.291

0.399

0.440

0.177

0.140

half landing hopper 100 X 30 cm

6.10

Q1-2

0.318

flat 2nd floor, sx grille 100 X 20 cm

8.90

Q2

0.235

-2.456

0.325

-4.676

0.376

-6.280

0.222

-7.550

0.175

-4.700

flat 2nd floor, dx grille 100 X 20 cm

8.90

Q’2

0.236

0.324

0.381

0.222

0.175

half landing hopper 100 X 30 cm

9.40

Q2-3

0.255

flat 3rd floor, sx grille 100 X 20 cm

12.20

Q3

0.162

-1.162

0.235

-2.460

0.300

-3.989

0.245

-5.370

0.193

-3.320

flat 3rd floor, dx grille 100 X 20 cm

12.20

Q’3

0.165

0.238

0.303

0.245

0.193

half landing hopper 100 X 30 cm

12.70

Q3-4

0.167

flat 4th floor, sx grille 100 X 20 cm

15.50

Q4

-0.024

0.057

0.081

-0.292

0.212

-1.989

0.231

-3.191

0.182

-1.984

flat 4th floor, dx grille 100 X 20 cm

15.50

Q’4

-0.043

0.088

0.217

0.231

0.184

half landing hopper 100 X 30 cm

16.00

Q4-5

-0.016

flat 5th floor, sx grille 100 X 20 cm

18.80

Q5

-0.180

0.524

-0.210

0.702

0.027

-0.037

0.153

-1.044

0.121

-0.650

flat 5th floor, dx grille 100 X 20 cm

18.80

Q’5

-0.188

-0.218

0.030

0.158

0.124

half landing hopper 100 X 30 cm

19.30

Q5-top

-0.248

roof — full louvered 260 X 90 cm

22.45

Qtop

2.562

3.755

-2.844

0.822

-2.224

0.515

-1.721

0.311

roof sx — full louvered 100 X 90 cm

22.45

Q’top

roof dx — full louvered 100 X 90 cm

22.45

Q»top

-1.456

-1.763

1.591

Further simulations were run in order to equalize and optimise the flow rates, by adding pressure losses at the unit entrance ventilation openings (step 4). The main results are presented in fig. 6. In addition the external temperature was set to 8°C in order to evaluate the airflow-rate changes (see step n.5 in table 1).

Tablel: Airflow rate from each opening and pressures.

The minimum air change rate is about 1.8-1.5 ACH, above the normal ventilation needs in winter for residential units [1]. Each occupant can manually adjust the air-inlets of some or all the rooms to suit personal requirements.

Sustainable CO2 Sink

Interior of the church

Already during the planning phase, the small complex proved to be innovative, particularly regarding the way it was built and the integrated, balanced optimisation of all aspects. Deliberate publication of the energy concept and its overall economic feasibility via the media, guided tours for visitors and the distinctive architecture take advantage of the position offered by a church building to disseminate the idea of sustainable building. And the message is heard: church attendance on Sundays was increased by a factor of five.

SHAPE * MERGEFORMAT

Section of southern facade

Lichtblau Architects, January 2004