News From Eight

Shining a light on the importance of daylighting

27/10/2015

Eight Associates offers a range of services related to Daylight Analysis including modelling of daylight conditions to assess for compliance with green building rating systems and Daylight and Sunlight Impact Assessments to provide guidance on the impact of new developments to daylight on neighbouring properties. This post discusses the role that skylights can play in improving daylight conditions.

The primary purpose of using windows and skylights is natural lighting and view – two factors which have an enormous impact on occupants. People like being in a day-lit space and having views of the exterior environment and the sky. Daylight is considered to be the best source of light. It provides high quality and levels of light, without flicker and the optimum spectrum and colour to which our eyes are best adapted.  It is also known to regulate and affect many physical functions of our bodies, including vitamin D production, endocrine system, hormone levels and cycles, and our “inner clock” circadian rhythm.  Quite simply, the use of daylight in buildings is essential to the wellbeing of users and also to meet health regulations regarding natural light.

Skylights are a great solution to improving the daylight conditions of a space: They generally result in higher illuminance levels than vertical openings and, unlike windows, skylights can also light the inner parts of deep spaces. Interestingly, skylights may result in more uniform light conditions (human visual performance stabilizes around 500 lux), decreasing the need for electric lighting and improving visual comfort.

Paradoxically, skylights could create issues that directly disturb a user’s comfort – and this should be addressed in the design process: One of the most common problems of skylights is the appearance of moving sun patches inside the room that can lead to thermal and visual discomfort.  Furthermore, skylights in general need more shading hours than windows to avoid overheating, especially during summer, while the absence of a shading system and the inability to control the light levels can counter the benefits of skylights due to high visual discomfort. These issues can be overcome by orienting and sizing skylights correctly, by using skylight wells, glare control systems or shading devices.

The integration of skylights impacts the building’s energy performance in many ways. Their sizing and position needs careful consideration; for example large areas of glazing may lead to excessive heat losses during the heating season and increased solar heat gains during the cooling season. However, correctly sized and oriented solutions can reduce electric lighting, heating and cooling requirements. These potential energy savings lead to lower operational costs – and rapid payback periods for the initial installation.

The utilisation of daylight through roof windows can greatly reduce the energy demand for electric lighting and indirect cooling demand generated by the heat from lamps, as long as the skylight’s overheating effect is controlled. The savings can be increased even more if photo-sensor controlled lighting systems are used. The reduction in heating demand comes primarily from the passive solar heat gains entering the envelope through the skylights (a more significant factor in cold climates). Moreover, the use of natural ventilation, so often preferred by occupants, leads to higher air exchange rates which improve indoor air quality significantly without the need for mechanical ventilation, and subsequently reduce operational costs.

Installing skylights will not, in itself, automatically unlock the benefits on offer. However, expertly sized and oriented, skylights provide a cost-effective, energy efficient daylighting solution – both as an alternative and supplement to vertical window openings. Moreover, they may result in a more comfortable environment, over which occupants have a greater level of control. They are a very visual imprint of a building’s sustainable credentials, potentially enhancing its overall desirability. It’s not a surprise therefore, that we are seeing more and more interest in incorporating skylights into commercial, residential and education projects.

Please get in touch on tel 020 3179 0420 or info@eightassociates.co.uk to find out more about daylighting solutions or if you’d like to discuss a particular project.