Importance of Daylight simulation in Green building Certification
What is Daylight Simulation?
A computer-based calculation of the amount of daylight available inside or outside of a building under one or several sky conditions. Simulation outputs may be discrete numbers (illuminances and luminances) under selected sensor points within a scene or visualizations of a scene.
Daylight is merely the visible part of the radiant energy that enters through windows. Furthermore, the bulk of the daylight energy that enters a space is converted into thermal energy after just a few reflections. Many office buildings in moderate climates now have air conditioning largely due to the high internal gains. In warmer climates cooling may be needed for large parts of the year.
Fig. Daylight analysis on design builder
Tools used for Daylight Simulation
Most of the software used today are based on radiance but have different interface. While there are a number of options available for daylight simulation, there are certain criteria that you should ask yourself before choosing the simulation software for daylighting.
1. What do you want to calculate?
2. Has the software been validated?
3. How easy is the software to learn?
Following are some tools widely used for Daylight simulation. There are other tools that exist too but these softwares are the most latest softwares used
Autodesk Ecotect is an environmental analysis tool that allows designers to simulate building performance.
DesignBuilder comprises a core 3-D modeller and 11 modules which work together to provide in-depth analysis for any building.
Diva for Rhino
DIVA-for-Rhino is a highly optimized comprehensive daylighting and energy modeling plug-in for Rhinoceros 3D.
Open Studio is a cross-platform collection of software tools to supports advanced daylight analysis using Radiance.
Green Building Credits
All Green Building Certifications require daylighting in a building, although it’s not mandatory for all buildings.
EQ Credit: Daylight
To provide building occupants with a connection between indoor spaces and the outdoors through the introduction of daylight and views into the regularly occupied areas of the building.
1. This compliance path incorporates two daylight metrics to determine daylight avaiability in the buildings. –
- Spatial Daylight Autonomy (sDA): sDA is a metric that defines a % of area that meets minimum daylight illuminance levels for a specified fraction of the working hours per year. In case of LEED v4, sDA300/50% indicates that a certain percent of area must meet or exceed 300 lux for at least 50% of the working hours per year.
- Annual Sunlight Exposure (ASE):
ASE is a metric that identifies the potential for visual discomfort in interior work spaces. For LEED v4, no more than 10% of a space should have direct sunlight more than 1000 lux for a maximum period of 250 hours per year (ASE1000/250).
A healthy balance between sDA and ASE can be achieved using design strategies to control glare such as shading devices.
Softwares that can prove compliance with LEED
Criteria 11: Achieving indoor comfort (Visual)
The intent of this criteria is to ensure that building spaces are designed to deliver visual comfort to building occupants.
This criteria has some mandatory requirements to it, i.e
- Minimum of 25% of the living area should meet adequate level of daylight (daylight factors) as prescribed in SP 41
- Demonstrate that the mean DA requirements (300* lux or more) are met over the total living area for at least 25% of total annual analysis hours (area-weighted) and mean DA requirements (3000 lux or more) are never exceeded over the total living area for across the total annual analysis hours
If the adequate level of daylight i.e daylight factors (DF) are achieved in more than the following(%) of total living area:
Mean DA requirements (300* lux or more) are met over the total living area for at least the following (%) of total annual analysis hour:
Softwares that can prove compliance with LEED
IEQ Credit 2: Daylight
Ensure connectivity between the interior and the exterior environment, by providing adequate daylighting.
The project can choose any one of the following options or a combination, to show compliance:
Option 1 – Simulation Approach
Demonstrate through computer simulation that 75% of the regularly occupied spaces in the buildingachieve daylight illuminance levels for a minimum of 110 Lux (and a maximum of 2,200 Lux)in a clear sky condition on 21st September at 12 noon, at working plane.Areas with 2,200 Lux or more daylight illumination levels should not be considered.
Option 2 – Measurement Approach
Demonstrate through daylight illuminance measurement that 75% of the regularly occupied spaces in the building achieve daylight illuminance levels for a minimum of 110 Lux. Areas with2,200 Lux or more daylight illumination levels shall be not considered.Measurements shall be taken after installation of furniture, equipment & systems at work plane height at 9 am, 12 pm, and 3 pm, on a 10 foot square grid. To show compliance, consider the average of the measurements taken at 9 am, 12 pm, and 3 pm.