Why is climate-based daylight modelling important?
Daylight modelling is the process of undertaking calculations to assess daylighting in respect of a particular building design. Because the number of daylight hours and angle of the sun varies by location, it’s important to carry out those calculations based on site-specific conditions. Climate-based modelling, therefore, is a technique developed to assess daylight provision based on building-specific location and orientation, and 365-day climate data.
When should climate-based daylight modelling be carried out?
When looking to meet the recommendations of EN 17037 ‘Daylight in Buildings’, climate-based daylight modelling is essential. It is also required as part of the Education and Skills Funding Agency’s (ESFA) Facilities Output Specification 2017, which forms part of Generic Design Brief for the Priority School Building Programme.
Daylighting can be a daunting concept to think about when designing a building, but it doesn’t need to be. While it is undoubtedly a complex subject - especially when accounting for the four different areas of daylight design covered by EN 17037 - seeking advice at an early stage and getting the benefit of daylight modelling calculations will smooth the process considerably.
The alternative is to avoid the cost of calculations and modelling exercises, because it seems like a saving. But if late changes have to be made to a design because something was not given proper consideration at the outset, the knock-on effects can prove even more expensive.
Using daylight modelling to help refine the client’s brief means the balance of facade glazing and roof glazing can be part of initial design concepts, addressing any overheating concerns and keeping electric lighting demand to a minimum. When whole-building performance is eventually addressed, these benefits will contribute to a positive outcome.
Which areas of EN 17037 is climate data most critical to?
Climate-based modelling is the preferred method for calculating daylight provision, or illuminance levels. This determines whether users can carry out tasks satisfactorily, and plays a part in determining the likelihood of artificial lighting being switched on. Daylight factor calculations can be used, but are less accurate.
Detailed calculation of daylight glare probability (DGP) - which is concerned with removing the probability of glare for building users, especially those who do not choose where they sit - is also more accurate using climate-based modelling.