Computer Daylight Simulations in Buildings by mikesanye


									     Proceedings of the 7th WSEAS International Conference on SYSTEM SCIENCE and SIMULATION in ENGINEERING (ICOSSSE '08)

                          Computer Daylight Simulations in Buildings
                                      School of Architecture
                                   The University of Sheffield
                            The Arts Tower, Western Bank, Sheffield
                                      UNITED KINGDOM
                                   Faculty of Civil Engineering
                                Brno University of Technology
                                    Veveri 95, 602 00 Brno
                                      CZECH REPUBLIC

Abstract: - Newly designed buildings should be optimized with respect to sufficient indoor illuminance and
solar protection against glare effect and indoor overheating. The optimized building design must be based on
solutions of many design alternatives and case studies, as well as necessary assessments should be carried out
in order to find optimum solutions which can be completed via the help of computer simulation programmes.
Some of the simulation programmes could be helpful for modelling of indoor daylighting in rooms and spaces
with various types of daylight systems and their positioning in buildings. The paper focuses on a series of
computer daylight simulations completed for the selected room with four different types of window openings
specified for optimizing the building design for daylighting.

Keywords: - Computer simulations, indoor comfort in buildings, daylighting, thermal comfort.

1 Introduction                                                     2 Computer Simulations
Daylighting in buildings is an actual design task. Many            The traditional systems such as openings of windows,
existing buildings need window retrofit to increase indoor         roof windows and skylights have been used in building
thermal and visual comfort [1]. Newly designed buildings           envelopes in roofs and facades to provide sufficient
should be optimized with respect to sufficient indoor              daylighting into spaces in buildings. In existing
illuminance and solar protection against glare effect and          buildings, such problems of daylighting inefficiency due
indoor overheating [2], [3].                                       to dimly lit internal spaces can be resolved by light guide
Daylighting in buildings require the following design              systems. In this paper, a comparison study is prepared to
considerations [4], [5]:                                           show the results of each specified system used (windows,
- Window geometry and glazing optical properties,                  roof windows and skylights) with regards to the
- Area and light reflectance of internal surfaces,                 assessment of indoor visual comfort in the selected room.
reflectance and geometry of surrounding obstacles,                 The computer simulations were completed via various
barriers and ground close to the building,                         software included in Radiance 3R8 [7] (see figures 2
- Window shadings such as blinds, shutters, etc.,                  and 3) and were based on CIE overcast sky on 1st
- Sky climatic conditions – overcast or clear sky [6],             March compared to sunny clear sky conditions on 21st
window positioning with regards to the South-North or              June at 12:00 with the following parameters considered:
East-West orientations.                                            - Reflectance of surfaces in the room ρ: 0.70 (ceiling),
The optimized building design must be based on                     0.50 (walls), 0.34 (floor) and 0.92 (light guides tube)
solutions of many design alternatives and case studies             - Transmittance of transparent parts τ: 0.90 (window,
which can be tested through building simulation via the            roof window, skylight cupola), 0.75 (diffuser).
help of computer simulation programmes. These                      - Size of the specified room 4x5x3 m (see figure 1) with
computer simulations could be helpful for optimising of            dimensions 1140 mm x 1400 mm of the transparent
the building design such as for modelling of indoor                parts for the daylight systems: window, roof window,
daylighting in rooms with various types of daylight                skylight, and tubular light guide of radii 710 mm.
systems and their positioning in buildings as well as              Window, roof window, skylight and light guide were
useful for modelling of thermal indoor climate.                    separately simulated in a central position with respect to
                                                                   the selected room geometry. Internal illuminace on the

        ISSN: 1790-2769                                      125                               ISBN: 978-960-474-027-7
        Proceedings of the 7th WSEAS International Conference on SYSTEM SCIENCE and SIMULATION in ENGINEERING (ICOSSSE '08)

working plane 850 mm over the floor level was
determined (see figures 2 and 3).

                                     d           b

                                                     a                             Window under overcast sky



                                                                                     Window under sunny sky

            Fig. 1 The investigated room selected
                   for the computer simulations
a -window, b -roof window, c -skylight, d -tubular light guide

3 Results
Computer simulations were completed as a comparison
study between the different window and skylights used
and their influence on indoor illuminance. The results in
simulations are compared in the following figures 2 to 6.
Maximal Emax, minimal Emin and average Eaver values of
internal illuminances are for the simulated positions of
                                                                                 Roof window under overcast sky
windows and sky lights presented in table 1; in figure 2
for vertical window and roof window; and in figure 3 for
skylight and tubular light guide.

Table 1 Maximal, minimal and average illuminances
              March 1, time 12:00          June 21, time 12:00
                 – Overcast sky                – Clear sky
              Emax    Emin Eaver          Emax    Emin     Eaver
 Type         [lx]    [lx]    [lx]        [lx]     [lx]    [lx]
 Window      1093.2   38.1       157.2   2208.1      154.9   453.8
             3787.0 70.6 558.4 67615.6 481.1 10327.5
 Skylight    1357.0 192.5 593.1 64961.7 422.9 10034.0
 Tubular                                                                          Roof window under sunny sky
 light guide 187.1 29.6 84.6 1907.1 327.5 885.1
                                                                                Fig. 2 Computer simulations with
                                                                                       window and roof window

          ISSN: 1790-2769                                            126                         ISBN: 978-960-474-027-7
Proceedings of the 7th WSEAS International Conference on SYSTEM SCIENCE and SIMULATION in ENGINEERING (ICOSSSE '08)

                                                             4 Conclusion
                                                             In the study, the computer simulations helped for the
                                                             optimization of the building design. The results obtained
                                                             from the daylight simulations carried out in a reference
                                                             room selected were compared with different daylight
                                                             systems such as vertical windows, roof windows,
                                                             skylights and tubular light guides and their possible
                                                             influence on the indoor visual comfort in buildings.
                                                             The graphical distributions of internal illuminances on
                                                             the working plane from simulations have shown that
                                                             skylights and roof windows presented higher illuminance
         Skylight under overcast sky                         values compared to vertical ones, however internal
                                                             daylight uniformity is much more suitable for window
                                                             design variations.
                                                             On the basis of the above presented results of the indoor
                                                             illuminance simulations conducted in a reference room
                                                             selected, it is obvious that tubular light guides represent a
                                                             better solution and a new alternative way to distribute
                                                             daylighting into internal spaces in buildings. Daylighting
                                                             in buildings with the light guides of shorter segments
                                                             mounted in a suitable positioning can be comparable with
                                                             traditional daylight systems.

                                                             The paper was completed within the frame of the bilateral
          Skylight under sunny sky                           collaborative project between the School of Architecture
                                                             at the University of Sheffield, UK and the Faculty of
                                                             Civil Engineering at Brno University of Technology, CZ.
                                                             The computer simulation studies were completed under
                                                             the support of the project GACR 101/05/H018, Research
                                                             of Efficient Systems for Indoor Climate Comfort.

                                                             [1] Thermie, Daylighting in Buildings, Project PUCD-
                                                                 OPET, UK, 1994.
                                                             [2] Ward, I.C., Energy and Environmental Issues for the
                                                                 Practising Architect - A Guide to Help at the Initial
                                                                 Design Stage, Thomas Telford Ltd., London, 2004.
   Tubular light guide under overcast sky                    [3] British Standards, BS 8206-2 Lighting for Buildings -
                                                                 Part 2 - Code of Practice for Daylighting, UK, 1992.
                                                             [4] Baker, N., Steemers, K., Daylight Design of Buildings.
                                                                  James James Science Publisher Ltd, London, 2002.
                                                             [5] Evans, B.H. Daylight in Architecture. Mc Graw-Hill,
                                                                  New York, 1981.
                                                             [6] Kittler, R., Darula, S., Perez, R., A set of standard
                                                                  Skies, Final Report of Project US-SK 92 052,
                                                                  Polygrafia SAV, Bratislava, 1998.
                                                             [7] Radiance 3R8 - Computer Simulation Program,

    Tubular light guide under sunny sky

      Fig. 3 Computer simulations with
          skylight and tubular light guide

  ISSN: 1790-2769                                      127                                ISBN: 978-960-474-027-7

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