Artificial lighting typically accounts for one third of a building’s CO2 emissions.

Maximising available daylight is a key element of a building design. Assessing the sunlight path and impact of a building on adjacent properties is also an important consideration when planning a development.

KJ Tait Engineers have the resources and experience in the design, simulation and analysis of daylight and sunlight assessment to accurately predict and show the behaviour of daylight and sunlight both internally and externally to a development.

We can provide daylight impact assessments to demonstrate compliance with the relevant standard (BRE, BREEAM, CBDM and Wellness Standard) or to assess the impact which new developments will have on the existing daylight and sunlight within adjacent properties and gardens for planning applications.

Capabilities and services available include:

  • Insight on sunlight availability to landscape areas
  • Daylight autonomy modelling
  • Visual comfort and view of sky studies
  • Inform energy models by predicting solar gain and artificial lighting needs
  • Climate-based Daylight Modelling (CBDM) Useful Daylight Index (UDI) and Spatial Daylight Autonomy (sDA) to optimise glazing ratio and orientation
  • Average Daylight Factor (ADF) calculation for BREEAM credit requirements
  • Spatial Daylight Autonomy (sDA) and Annual Sun Exposure (ASE) calculation for the Well Building Standard requirements.

Daylight & Sunlight Impact Assessments for Planning

For most new urban developments, it is necessary that a daylight and sunlight impact assessment will be required for submission to the local planning authority.

These assessments are required to ensure that the quality of daylight and sunlight at adjacent properties and gardens is not significantly impacted upon by the new development and can include the following:

  • Review proposed and existing view of sky line
  • Assessing the quality of internal daylight within a proposed building
  • Predicting the daylight/sunlight impact of a development at the windows of adjacent buildings
  • Predicting the daylight/sunlight impact of a development on adjacent public areas, gardens or development land
  • Right of Light assessments at existing dwellings (England only).

This is typically assessed through using modelling software to accurately build a 3D model of the proposed development and adjacent areas to allow us to predict the Vertical Sky Component (VSC) values at the existing dwellings before and after the proposed development.

Spatial Daylight Autonomy (sDA) and Annual Sun Exposure (ASE)

Calculation for the Well Building Standard Requirements

The WELL building standard is a leading tool for advancing health and wellbeing in buildings globally. WELL’s flexible framework aims to improve health and human experience through design.

The WELL building standard stipulates criteria to find a balance between sDA, which measures the percentage of floor area that receives adequate sunlight, and ASE, which measures the percentage of floor area receives too much direct sunlight.

To achieve the desired credit, analysis is carried out using 3D modelling software to simulate the amount of sDA and ASE within an area.

Average Daylight Factor (ADF) Calculation

Average Daylight Factor (ADF) calculations demonstrate how the level of light inside a building compares to the level of light outside and estimates how much light will actually reach occupants of a building. ADF calculations are a common requirement for the BREEAM assessment.

BREEAM Health and Wellbeing criteria stipulates the minimum daylight requirements within occupied areas of a building. To achieve the desired credit, daylight analysis is carried out using software to simulate the amount of available daylight within an occupied space.

Climate Based Daylight Modelling (CBDM)

KJ Tait Engineers work with leading Architects and construction companies, as part of the UK Governments Education & Skills Funding Agency (ESFA) Priority School Building Programme (PSBP).

All new ESFA funded school developments are required to meet the ESFA specification for the provision of adequate daylight to teaching spaces and other occupied rooms.

Climate Based Daylight Modelling CBDM is a highly complex and accurate method of daylight analysis which analyses the available daylight through a school day. This is a crucial tool to influence the internal space planning and external façade design of school buildings to ensure adequate daylight is available within a classroom during the school day throughout the year. CBDM uses two criteria to assess this.

The first criterion sets a Useful Daylight Index (UDI). This is detailed as the annual occurrence of illuminance across the work plane that is considered “useful”.

The second criterion calculates the Spatial Daylight Autonomy (sDA). This is the amount of time a space can expect to reach a target illuminance level on the working plane.

As recommended in the EFA guidance for schools, the calculation will be carried out over the course of an entire year including weekends and the holiday period between the hours of 8:30am and 4.00pm.

Internal and external obstructions immediately associated with the rooms will be included within the simulation.

Centre for Health Science, Inverness - glass roof

Get in Touch

Please get in touch if you have a general query or you would like us carry out daylighting and sunlighting analysis for your project.

We offer a comprehensive daylighting analysis in addition to our MEP Engineering design services and would be pleased to get involved in the planning stages of a project to inform the design process as early as possible.

We can also offer a short presentation to your team on any aspect of daylight modelling and planning requirements which can be arranged at a time to suit you.

Contact Details



T: 0131 225 7117 (Edinburgh Office)