Daylight and glare

With increasing concern over global warming and carbon emissions, monitoring the level and quality of natural light in buildings plays a pivotal role in environmental programs and design, such as BREEAM, LEED and Home Quality Mark.

Why should you assess daylight and glare?

Sunlight can have dramatically positive effects on human behaviour. But despite its advantages, daylight needs to be controlled to optimise its use - and artificial light is always needed.

While daylight can reduce the amount of electric light needed to adequately illuminate a workspace and reduce potential energy costs, allowing too much light or solar radiation into a space can have a negative effect, resulting in heat gain and offsetting any savings achieved by reduced lighting loads.

Office artificial lighting

Daylight and glare expertise

We carry out assessments for every hour in the entire year. Our dedicated team have many years of experience investigating the effects of different parameters on daylight and discomfort glare prediction.

To review daylight and glare impact within the built environment, we carry out daylight assessments that compare the impact of building orientation, window frame factor, window size, overhang and G-value on daylight quality and intensity. Our team can provide innovative and sustainable integrated daylighting with efficient electric lighting strategies to provide substantial energy savings.

 

What is daylight and glare?

Daylight – light provided by the sun is divided into direct sunlight and diffuse skylight; light modified and distributed by the atmosphere. Daylight quality and intensity depends on:

  • Geographical latitude
  • Month and hour of a day
  • Local weather
  • Sky conditions
  • Building geometry
Daylight in office

GlareGlare is defined as the condition of vision in which there is discomfort or a reduction in the ability to see significant objects due to an unsuitable distribution or range of luminances. Discomfort glare indices are based on:

  • The luminance of the glare source(s) in the field of view
  • The solid angle of the glare source(s)
  • The luminance of the background
  • The position index of the glare source(s)
Daylight glare on building

Positive effects of daylight

Biological effects – Daylight can affect our biological clocks, sleep and activity. Many manufacturers are using artificial lighting to simulate external conditions to prevent diseases, stress, fatigue and tiredness.

Thermal effects – Window and lighting systems can affect building thermal loads. Having lighting control systems can reduce the cooling demand; such as decreasing lux when daylight watts are enough or using shading devices when the room is not occupied in the summer, and reversing this in winter.

Energy saving – In the built environment, we benefit from using solar energy in various ways, such as heating and lighting. Building energy consumption can also be reduced by daylighting, a strategy in modern architecture where natural light openings are factored into design to replace or supplement artificial lighting. Daylight itself does not increase energy saving but when paired with lighting control strategies (manual, timed and automatic controls) or photo sensors it can significantly lower energy costs.

 

Assessing daylight and glare

How do you assess daylight?

Daylight design is rapidly moving forward and can now provide information that accommodates all of the requirements of the daylight consultant, architect and end-user. The ideal package should integrate natural lighting and electrical lighting calculations and take into account an evaluation of the thermal impact on window design.

The amount of daylight inside a room can be measured by comparing it with the total daylight available outside the room. This ratio is called daylight factor (DF) which can be measured in percentage (%).

The value of daylighting factor (DF) depends on building types, window sizes, frames and position, types of glazing, transmission characteristics of glazing, cleanliness of glazing and interior room surface reflectance.

How do you assess glare?

When studying discomfort glare, the most common method is to compare subjective glare ratings that are made on discomfort glare scales, and the values of discomfort glare indices calculated from measured physical quantities.

To measure these quantities efficiently, radiance is simulated to create a 180◦ luminance map containing the subject’s field of view. Discomfort glare indices are then calculated afterward on the basis of these luminance maps. The calculation of discomfort glare indices based on a luminance map is an essential step and an inherent part of discomfort glare studies.

We conduct detailed glare analysis to create High Dynamic Range (HDR) renderings within a site or building facing that is fitted with PVs or other obstacles. The simulation results are then analysed to explore the effect of glare on occupants’ visual comfort. We then produce a detailed conclusion of the study and discuss future studies required to improve visual comfort in dense urban areas.

What you need to know about daylight and glare

  • It is important to integrate disciplines to streamline daylighting design, including architectural, mechanical, electrical and lighting. Teams should be brought into the design process early to ensure that daylighting concepts and strategies are implemented throughout.
  • The lighting system must correlate to the various systems in place, including structural, curtain wall, ceiling, and furniture. The building's planning module can often give indications on how best to organize the lighting.
  • Initial lighting costs may rise when designing for sustainability and implementing energy-efficient strategies. These energy-saving designs may require items such as dimmable ballasts, photocells, and occupancy sensors, all of which are not typically covered in most traditional project budgets. However, these items are normally included if an integrated design approach is employed and if daylight strategies are appropriately employed at an early phase of the project's design.
  • Glare should be considered when contemplating the massing of a building or a larger development. This requires evaluating the geometries and surfaces of neighbouring buildings with specular facades, potential secondary and tertiary reflections, the Earth’s movement in relation to the sun, local topography, viewing points, and types of public and transport spaces.

 

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