daylight analysis: a case study on the snowdon visitor centre in...

Daylight Analysis: A case study on the Snowdon Visitor Centre in Wales

Dong Hyun Kim

Doctoral ResearcherInstitute for Environmental Design and Engineering (IEDE)The Bartlett School for Environment, Energy & Resources, UCL, UK

45th International HVAC&R Congress and Exhibition

UCL Institute for Environmental Design and Engineering

Objectives of the case study

• What is ‘good daylight simulation’?

• What aspects of daylight needs to be considered?

– Adequacy of daylight

– Solar design

• How can we improve the current daylight simulation?

The Snowdon Visitor Centre – Why?

• Extreme site condition• Extreme weather condition


Adequacy of daylight is first analysed.

Are there enough daylight in the visitor centre?


Adequacy and Daylight Factors

Where daylight adequacy is an issue in design, in the UK, requirements are usually given in terms of Daylight Factors.

Current Recommendations for Daylight Factors

Min (Av) Daylight Factor

Mainly daylit (during working hours) 5%

Daylit but will require some supplementary lighting) 2%

Domestic Interiors

Kitchen 2%

Living Room 1.5%

Bedroom 1%


Surface Material Reflectance (R)

Area (m2)

Reflectance * Area

1 Timber 0.25 39.2 9.8

2 Timber 0.25 38.3 9.58

3 Double glazing; including dirt

0.1 16.1 1.61

4 Openings 0.05 26.5 1.33

5 Timber 0.25 45.2 11.3

6 Double glazing; including dirt

0.1 40.8 4.08

7 Granite tiles 0.2 184.7 36.94

8 White fabric ceiling

0.8 215.5 172.4

9 Columns / Fen-estration

0.75 264.6 198.45


West-facing window East-facing window

Overall average DF is 3.1

Is there enough day-light?

• minimum recommendation on daylight factors (SLL)

What about distribution of daylight?


Adequacy analysis –daylight factor (DF) by diagrams


Adequacy analysis –daylight factor (DF) by scale model


Adequacy analysis –daylight factor (DF) by computer simulation programme (AGI32)


Point DFAGI32 Point DFAGI32

1 1.9 10 1

2 2.6 11 1.5

3 2.8 12 0.7

4 2.9 13 0.8

5 2.9 14 0.9

6 1.4 15 0.9

7 1.6 16 0.9

8 1.6 17 0.8

9 1.5 18 0.7

Results on Daylight factorsDFs from BRE sky protractor

DFs from the sky simulator

• Similar results are shown. • A spread of 2-4% daylight factor in the areas

surrounding the west facing window. • Areas below 2% will benefit from electric lighting.


DFs from AGI32

What does the result suggest?

• Meet the minimum recommendation level of daylight factors• How to increase the daylight factors (to minimize the use of electric lighting)?

● Change the interior materials ● Raise the height of the roof


Adequacy of daylight is now evaluated.

What about the solar gains or presence of sunlight?


Solar analysis: Sunlight availability (1)

• Shading effects plotted on the protractor and superimposed over a sunpath diagram

• Solar control is effective from● 10:00 to 14:00 (Jun 21st)● 10:50 to 13:00 (Mar/Sep 21st)● 11:50 to 12:10 (Dec 21st)●

• Solar control is more effective during the summer months due to the reduction in width towards December


Solar analysis: Sunlight availability (2)

• Each dot represents 0.2 probability of there being sunlight penetration

• In the summer half (red dots), the probability of sunlight penetration is 48%, which is 24% lower if the solar shading was not there.

●

• In the winter months (blue dots), the probability of sunlight penetration is 21%, which is only 4% lower than if the solar shad-ing is not there.


Solar analysis: artificial sky simulator (1)10:00 to 11:00 11:00 to 12:00 12:00 to 13:00 13:00 to 14:00

Jun 21st

Mar/Sep 21st

Dec 21st


Solar analysis: artificial sky simulator (2)17:00 to 18:00 18:00 to 19:00 19:00 to 20:00 20:00 to 21:00

14:00 to 15:00 15:00 to 16:00 16:00 to 17:00 17:00 to 18:00

14:00 to 15:00 15:00 to 16:00



Results to design suggestions?

• What about extending the overhang of the roof or modifying it incorporates a louvre system to interrupt the direct sunlight into the space?


Results to design suggestions? (2)

• A minor refinement to the east-facing window up-stand in order to increase the daylight factor at deeper points in the plan


The comparisons of the methods

Methods Advantages Disadvantages

Average Daylight Factor (BRE310)

• Quick method • Not very precise• Not provide information for distribution of

daylight in the interior• Not provide information of solar aspects of

daylight in the interior

Physical scale model

• Solar shading is well evaluated and the results can be compre-hended

• Requires great precision• Time consuming • Difficult for complicated buildings• Without the artificial sky simulator, results

under the real sky cannot be very precise

BRE protractors

• Provides a better understanding of the components that from the daylight factor

• Time consuming if there are many points to be calculated

• Not provide information of solar aspects of daylight in the interior

Computer simulation

• Relatively quick• Could measure numerous points

of daylight factors

• Results should be considered with skepticism and if possible compare to another method

• Entry barriers for the non-simulating expert


• Good daylighting simulation should help the designer to choose their alternatives or to find a particular solution.

• Current daylighting simulation softwares are often used at relatively late design stage, focusing on verification of the design.

• Simple tools are needed to help with the interactive design of good buildings that can take place in early stage of design.

• The gap between daylighting design and engineering solutions needs to be narrowed down.

Conclusion


Thank you

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