Day Lighting Factor
The Daylight Factor (DF) is a measure of the illuminance available inside a space as a percentage of the simultaneously available outdoor illuminance under a standard overcast sky. A DF of 2% at the workplane is generally considered the minimum for a naturally lit environment; above 5% is considered well-daylit.
In Indian office design, glazing orientation is a critical variable. East and west facades receive intense direct sun that a high DF alone does not capture. LEED for Interiors requires daylight simulation modelling to demonstrate 300 lux at 75% of regularly occupied spaces for a minimum number of hours. In a Viman Nagar fit-out facing west, external solar shading may be required to achieve both DF targets and thermal comfort simultaneously.
Related terms
Learn more
Certifications and Standards Relevant to Indian Commercial Interiors
How Day Lighting Factor fits into an office project
Day Lighting Factor matters when a workplace moves from a broad design idea to a coordinated brief. The team should define what the term means for this project, where it appears in the drawings or specifications, and who approves it. That prevents a familiar word from hiding a gap in scope, procurement, installation, or handover.
Questions to settle early
- What outcome should Day Lighting Factor support for the people using the workplace?
- Which drawings, schedules, samples, or calculations will confirm the requirement?
- What needs to be coordinated with architecture, interiors, MEP, technology, or building management?
What to record in the project brief
Record the selected approach, responsible owner, approval point, relevant exclusions, and the evidence required at installation or handover. If the requirement affects cost, lead time, maintenance, safety, comfort, or future flexibility, state that connection plainly. The definition is a starting point. The project brief turns it into a checkable decision.
A practical checklist for Day Lighting Factor
When Day Lighting Factor appears in a workplace brief, avoid treating it as a standalone line item. Connect the requirement to the people, spaces, services, and operating routines it is meant to support. A short definition is useful for orientation. A good brief also explains the project context, the expected performance, and the evidence needed before approval.
Before design sign-off
Confirm the existing site condition and any landlord or building-management rules that affect the decision. Mark the requirement on the relevant plans and schedules. Check interfaces with adjacent trades, access for installation, maintenance access, replacement cycles, and the effect on the programme. If alternatives are possible, compare them on whole-life suitability rather than headline purchase price alone.
At procurement and handover
Keep the approved specification, supplier information, samples or calculations, and agreed exclusions together with the project record. At handover, verify that the installed result matches the approved design and that the client receives the information needed to operate and maintain it. This makes Day Lighting Factor a useful control in delivery, not just a glossary phrase.
For a project-specific discussion, start with the Vektor Spaces services, review the delivery process, and bring the relevant questions to a project enquiry.
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