Daylight optimization

The benefits of daylight

Recent studies have shown that on average, people spend 90% of their time indoors. As daylight has a positive influence on people’s health, productivity, ability to learn and overall well-being , the rooms in which we work and live must maximise the amount of natural light while controlling the amount of solar gain to avoid overheating. Careful window specification is key to achieving this goal, and will help deliver the ideal indoor climate.

Design with daylight

The term “daylighting” refers to an architectural design strategy which allows natural light into buildings. Daylighting is an important part of sustainable design as it connects buildings users with the outdoors reducing the need artificial lighting, thereby improving health and supporting energy savings.


Effective incorporation of daylighting into building design should start early in the planning phase and requires a combination of advanced technical skills and mastery of traditional design and construction principles. One of the architect's most important tasks is to position the building so that daylight is optimally used and suits the functions of individual rooms. 

Important factors for optimizing daylight levels



The daylight factor (Df)

In architecture the daylight factor is the ratio of the light level inside a building to the light level outside the building at the same time of the day under overcast skies. The higher the Df, the more natural light is illuminating the room. The general rule of thumb for effective daylighting in a room is to make sure that the amount of glazing installed equals 10-20% of the floor area. Windows installed at height provide the opportunity for better light distribution




Window orientation

Allow daylight into a building from every direction, especially through windows installed at height. Ideally choose windows with a slim frame profile and high glass-to-frame ratio. The shape, size and position of every window within a façade will have a significant impact on the distribution of daylight across every room. Avoid placing transoms or glazing bars within the field of view


Existing features such as neighbouring buildings, hills and trees can affect the amount of daylight that penetrates a window. To maximise the energy performance of the windows it is therefore essential to take existing shading into consideration at the early design stage.




Sun screening

Low-energy buildings need to maximise their use of free solar heat. However, if not controlled effectively, passive solar gain can result in the overheating of spaces within the building. It is therefore essential to control the amount of solar gain entering a building during the summer months by adding sun screens to the windows. There are many options available on the market, including internal, external and automatic screens, but whatever your choice, we suggest using flexible solutions that don’t affect the view.




Daylight and seasonal changes

Daylight is a challenging element to work with as it changes - both during the day and across seasons. When talking about daylight, a distinction must also to be made between the diffuse light experienced on a gray day, and direct sunlight, characterized by a warm light with shadows and greater contrast. Buildings must be designed to take both scenarios into consideration ensuring a sufficient flow of daylight in the winter without having to struggle with overheating in the summer months.




The power of light and shadows

The purpose of architectural lighting is to enhance the overall spatial experience. Both light and shadows are necessary to establish the limits of a space , and when used effectively they can also create a comfortable environment in which to work or live.  The use of too much colour or pattern into the internal spaces can detract from the architectural shapes and obscure the details, while the contrast between the light and dark creates depth. In this context, daylight can then be seen as part of an aesthetic whole, as it interacts with the surrounding colours and surfaces adding drama and energy, or creating texture and mood.




Daylight case study: Benefits of daylight in a healthcare environment

Daylight is important in any setting, but especially in the healthcare environment. At Casa-Di-Lusso nursing home, slim framed VELFAC windows and doors are used to bring warmth, comfort and natural light and provide a focal point for every room.


Increase levels of light with VELFAC windows

Narrow frames let in more light

Daylight and energy performance are among the most important features of a window. The higher the proportion of glass in a individual window, the more light will enter the building, reducing the need of artificial lights. Windows with a high ratio of glass to frame (or a high Ff value) will allow a greater amount of solar heat and daylight to enter the building. Windows with the same overall dimensions, but with larger frame profiles have a lower percentage of glass and therefore restrict the passage of light and heat.


VELFAC windows feature a 54mm frame construction and a high proportion of glass, which significantly improves light penetration





Unique construction designed to let more light in



VELFAC 200 is a beloved design classic in both the UK and the international market.


The unique 54mm “floating frame” deliver excellent performance and maximises the amount of daylight entering the building thereby reducing the need for artificial light and heating.






Achieve optimal indoor climate and meet your energy targets

We provide a range of services designed to ensure impressive performance levels, backed by advice and guidance on technical issues and regulatory compliance.


More inspiration and knowledge

Fact sheet More daylight, less heat

Download our fact sheet and learn how to avoid overheating, regardless of fenestration.


"We wanted to make sure the building could stay comfortable without the need for mechanical cooling, even through the hottest summer. ‘This meant the placement of smaller windows on south facing facades, to manage solar gain, and the specification of multiple opening units across the building, including high level teleflex-operated lights."


- Corrie Rounding, Architect, Innes Associates


Contact our team to receive
Consultancy and advice for your project

Our team of experts can help you achieve your performance targets by providing tailored advice based on windows position, room orientation and specific requirements for your project