Daylight

Peter Raynham FILP

Daylight: provides light for tasks

Daylight: attractive

environment

Daylight: can go wrong

Earth’s Orbit

Daily Variation

Annual Variation

Sun Elevation and Azimuth

Daylight Availability

Daylight Availability

Average Daylight Availability

Median Daylight Availability

• The amount of daylight that is available for half of the time.

• For London 14,100 lux

Daylight factor

General Requirements

• DF – 2% start of daylight appearance• DF – 5% daylight provides nearly all of the

light needed

• Median Daylight Illuminance 300 lx

Windows

• Contact with outside world• View in View out• Let daylight in• Thermal properties

Contact With Outside World

View In View Out

View In View Out

Let Daylight In

Energy Savings

• Key factors– Daylight availability– Daylight penetration – Lighting control system– User satisfaction

Is Daylight Beneficial?

• Study in a London School• Background• Key points• Findings

Background

Küller, R.; Lindsten, C. (1992). Health and behaviour of children in classrooms with and without windows. J. Environ. Psychol. 12, 305-317

Showed:• Children in classrooms with daylight show

different annual variation in levels of cortisol

Background

Hershong, L., Wright, RL. and Okura, S. (2002). Daylighting impacts on human performance in school. Journal

of the Illuminating Engineering Society Showed:• significant effects of daylighting on the

performance of school students

Background

Govén, T., Laike, T., Pendse and B. Sjöberg, K. (2007). The background luminance and colour temperatures influence on alertness and mental health. CIE 26 Beijing

Showed:• ambient light is of upmost importance

Key Points of the Study

• 4 form entry primary school (~120 pupils per year)

• Pupils age 7 to 8• Test of impact of light (natural and electric)• Variety of pupil impact measures• Year long study

Daylight Factors

Electric Lighting

Study DatesMain Dates Supplemental Dates

8th October 2008 5th November 2008

9th December 2008 14th January 2009

10th February 2009 4th March 2009

25th March 2009 29th April 2009

20th May 2009 10th June 2009

Dates of data collection

Study ActivitiesTimes Operations

08:00-08:50 Preparations

08:50 The start of school day – Subjective sleep quality reports*

09:50 Subjective mood and sleepiness reports & Saliva samples*

10:15-10:30 Morning break

11:45 Subjective mood and sleepiness reports + Saliva samples

12:00-13:10 Lunch break

14:45 Subjective mood and sleepiness reports + Saliva samples

15:20 The end of School day

Daily routine for the main collection days* Supplemental collection days

Pupils in the Study

Pupil Numbers

Classrooms

Total

C1 E1 E2 C2

The number of participating pupils 14/30 11/29 16/29 15/29 56/117

The number of participating male pupils 7/15 7/14 9/14 7/15 30/58

The number of participating female pupils

7/15 4/15 7/15 8/14 26/59

The number of pupils in the study

Overall Avarage Mood Scores

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

08 Oct. 09 Dec. 10 Feb. 25 Mar. 20 May.

Date

C1

C2

E1

E2

Overall Avarage Mood Scores

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

08 Oct. 09 Dec. 10 Feb. 25 Mar. 20 May.

Date

DF ~2%

DF ~5%

C1

E1

E2

C2

Prog Jan

Prog May0

0.5

1

1.5

2

2.5

3

Progress in Wrting

The analysis of the monthly trend of the cortisol levels at 09.50 revealed a significant difference between months contrast (F(1,22)=8,087, p=.009) and a significant difference between the rooms (F(1,22)=4,969, p=.036)

Findings OverviewAnalysis is being finalised a paper in LR&T should be

published later this yearGeneral findings:• The pupils with more daylight did better than those

with less• In the rooms with less daylight the higher level of

electric light helped during the winter• In rooms with more daylight extra electric light

made no difference

Conclusion

• Daylight is a free resource• We should us it with care• It can save energy• It can provide a view• People like daylight• Daylight can improve performance