8.0 Daylight and Sunlight in Scotland

Designing a daylit sports hall requires information on the availability of daylight and sunlight, to enable energy consumption and construction costs to be calculated. The feasibility of a potential sports hall will depend largely on whether or not the intended daylighting strategy is going to save money or cost more (capital cost and running costs) than a non-daylit sports hall.

Glazing is always more expensive than a plain wall or roof, in terms of capital cost. It also has poorer insulation levels, not taking into account the potential for solar gain through a correctly orientated window.

Scotland is around 200 miles long, from North to South. This slightly affects the times that daylight is available in different parts of the country; the Orkneys have longer daylight hours in summer (by about 20 minutes on the summer solstice) than Dumfries, for example; but shorter daylight in the winter. The weather conditions are also different around the country; affecting the hours of available sunshine. The west coast receives more rainfall than the east, and correspondingly less sunshine.

8.1 Daylight Hours

To give the designer an idea of how successful the proposed sports hall will be, in Scotland, the daylight availability; sunrise and sunset times, have been included. See Appendix B for a table of daylight hours, based on Glasgow data (South West Scotland). Daylight times for North East Scotland can be estimated by adding 20 minutes to summer solstice times and subtracting 20 minutes for winter solstice times. Times in-between the solstices will need to be extrapolated accordingly. The far north of Scotland has daylight hours totalling one hour per day more or less; summer or winter solstices.

However, generally there is little effect in the amount of actual daylight hours over the whole of Scotland, in terms of energy savings in lighting, as the light levels available late afternoon/evening will need to be supplemented by artificial lighting to a greater extent.

8.2 Sunlight Hours

The predominant sky condition for Scotland is overcast or partially cloudy. This reduces the available direct sunlight and the corresponding problems associated with it. When the sun does shine it will create problems, especially in the winter months, when the altitude of the sun is low in the sky.

However, the amount of sunlight does vary across Scotland, with the south and west being cloudier than the north east. In general the following sunny sky frequencies are:

The diagram shown in fig. 8.2.1 shows the sunpath for Scotland, based on data gathered at Edinburgh and Glasgow. There is very little difference in the sun path, as far as buildings are concerned, between the south and north of Scotland. The difference is approximately 2 degrees less in the far north compared to the sunpath diagram shown.





				The sunpath diagram for London is about 3 degrees higher for each month than the Edinburgh. Calculations and methods for using the sunpath diagrams can be found in many publications, and will be discussed in the next stage of work when calculations are done on the proposed Scottish sports halls. 8.3 Potential Energy Savings The amount of daylight available can be related to the energy savings if daylight linking is used in the lighting controls. Correspondingly, there are greater savings in summer compared to winter, and the hours of daylight can be used to show how long the lights would need to be on.
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