Climate Based Daylight Modelling

Climate Based Daylight Modelling (CBDM) is a simulation of the quality and quantity of daylight within the space available in a room. It is carried out using real weather data for the location in question, over 365 days. The resulting information can be used for several purposes within the design process, which are detailed below. 

Priority Schools Building Programme
The Education Funding Agency recognises that good quality daylight is essential in a learning environment. To that end, all schools in the Priority Schools Building Programme must be able to demonstrate, using CBDM, that the room receives adequate daylight across the entire room, without incurring glare from excessive light near the window. BCM have developed streamlined and simplified processes for FOS compliance at ITT stage to save contractors time and money. 

Modelling Energy Savings 
In many buildings, artificial lighting is switched on at the beginning of the day and switched off when the building is vacant at night, regardless of the daylight conditions. CBDM provides a quantified basis for a lighting strategy, automating or sectioning artificial light to minimise use when there is no need. 

Up to 70% of lighting costs can be saved by maximising daylight and ensuring artificial lighting is only used when necessary. BCM can provide objective data to support business cases for occupancy and illumination sensors on artificial lighting systems, to lower energy costs and carbon emissions. 

Better Daylighting Design 

Traditionally, Daylight Factors would be calculated to measure the % of natural light available to a room. However, this can be misleading as it ignores the sun position and sky conditions which are critical in reality.

Large windows may result in a greater daylight factor, but is also likely to cause the nearest occupant to close the blinds due to glare, defeating the object. Badly placed windows can return an acceptable daylight factor, while parts of the room may be insufficiently illuminated.

Performing CBDM analysis can guide architectural and services design, providing objective data to support window location and sizing, to ensure occupant enjoyment and productivity in a space, and energy savings from lighting controls are realised by the end user.