Introduction
Sunlight is one of the main natural elements to consider when designing a building. It directly affects user comfort, energy performance, and the overall quality of a space. Thus, understanding how the Sun moves across the sky throughout the day and year allows architects and designers to enhance daylighting, manage solar gain, control glare, and improve building efficiency.
There is much data, diagrams, and mapping to enable us to design a detailed strategy to maximise on the natural benefits of the Sun’s rays. Sun path diagrams help provide us with a visual way of understanding the impact the Sun has on our site and our proposed building. Using both traditional Sun path diagrams and 3D CAD software we are able to learn a lot about our potential site. Considerations like overshadowing for urban sites, along with potential glare from reflections of other building facades are among the factors we can examine.
In this post we will be looking at the fundamentals of sunlight and solar gain. We will also demonstrate how we can use tools like Sun path diagrams to enhance our site analysis. So, stick around for some cool tips and visuals that you can apply in your next site analysis or design project.
Scroll to the end to download this article as a handy PDF guide!
Benefits of Natural Lighting in Our Buildings
Natural light in our buildings is known to improve occupant comfort. Scientists suggest that good natural light can increase occupant productivity and comfort, providing the mental and visual stimulation necessary to regulate the human circadian rhythms. Implementing natural light into a design also leads to substantial energy savings, by way of reducing the electricity requirements for artificial lighting. It is also possible to install daylight sensing controls to a lighting design to further reduce energy usage by between 20-60%.
As long as glare is controlled and solar gain accounted for and designed appropriately there is no question that natural lighting will improve occupant satisfaction, mood, and productivity. Studies suggest that human beings living in modern cities now spend upwards of 90% of their lives indoors. Knowing this makes it more important than ever to ensure we are allowing users to experience the natural outdoor cycles and variation of illuminance levels from within the buildings.
Sun Position and Path
[All data and information is based on a location of London, Latitude: 51.50741, Longitude: -0.12770]
The angle of the earth’s axis is 23.5˚ relative to the plane of its orbit around the Sun. But this angle changes, varying between 22.1 and 24.5 degrees over a period of about 40,000 years due to gravitational interactions.
This axial tilt is the main reason we experience seasons. Different parts of the planet are exposed to different amounts of sunlight as the Earth orbits the Sun. Although the Earth’s distance from the Sun changes during its orbit, this has little effect on the seasons. Instead, it is the axial tilt that causes the Sun to appear at different positions and angles in the sky depending on the time of year and your location on Earth.
There are key astronomical events that mark the extremes of this tilt: the solstices and the equinoxes. You may be familiar with the summer solstice at Stonehenge, where people gather each year to witness the sunrise align with the monument’s Heel Stone. This alignment marks the longest day of the year and reflects ancient understanding of the Sun’s path across the sky.
There are four of these key astronomical events in total that occur across the course of a year. It is also important to note that while the dates of these events stay consistent, the associated seasons are opposite in the Northern and Southern Hemispheres.
Solstices occur when the Earth’s tilt is most pronounced toward or away from the Sun. At the June solstice, the North Pole is tilted toward the Sun, resulting in the longest day of the year in the Northern Hemisphere. While at the December solstice, the South Pole is tilted toward the Sun, giving the Southern Hemisphere its longest day.
Equinoxes happen when the Earth’s axis is not tilted toward or away from the Sun, so both hemispheres receive equal sunlight. Here day and night are nearly equal everywhere on Earth.
Now in terms of the Sun’s position, we often use two angles named the ‘azimuth’ and the ‘elevation’ or ‘altitude,’ to describe where it appears in the sky at any given moment.
The ‘azimuth’ is the projection on a plan of the position of the Sun measured from north 0˚. As seen in the image below, east is 90˚, south is 180˚ and west is 270˚. It is basically what you see on a compass.
The ‘elevation’ angle is the projection of the position on the elevation of the sun above the horizon. It may also be referred to as the ‘altitude’ angle. As seen in the image below it ranges from 0˚ (at the horizon) to 90˚ (directly overhead). The 90˚ position is called the ‘zenith’ and is the highest position the Sun can be at.
The diagram below shows you the angles of the Sun during the solstices, and equinoxes for London. You can produce such diagrams for your particular site to show that you understand your site.
Sun path diagrams help us to pinpoint the position of the Sun throughout the year at any given time and also trace its movement. A key thing to note is that the Sun path is represented differently based on the hemisphere your site is in. In the northern hemisphere, the Sun rises in the east, moves across the southern sky, and sets in the west. This makes the south-facing sides of a building the sunniest. Whereas in the southern hemisphere, the Sun still rises in the east but travels across the northern sky to set in the west. This means the north-facing sides of a building will receive the most sunlight.
You can use one of the many online Sun path calculators to extract Sun related data for your specific site. These allow you to select your site location, desired time of day, and even adjust the dates to match those of the solstices and equinoxes. They also provide more data like the sunrise and sunset times in table format for your reference.
In this post, we have used data extracted from SunEarthTools.com. We have input the following location:
London, Latitude: 51.50741, Longitude: -0.12770
In 2025, for the northern hemisphere where our location falls in, the key astronomical dates are:
Vernal Equinox – March 20
Summer Solstice – June 21
Autumnal Equinox – September 22
Winter Solstice – December 21
These are the exact dates for the year 2025, but if a high level of precision is not really required, you can refer to the general seasonal dates outlined by the online calculators. The choice depends on the level of accuracy and context your project or design needs.
When using Sun data in design, we can simplify the diagrams from the online tools to extract key data. For instance, we have used the sunrise and sunset times on the solstices and equinoxes in 2025 to create the following visualisations.
Using the simplified Sun path diagram and merging them into one we can apply it to a design scheme. The data can be adapted for a whole building design, or to measure the exposure of a particular opening.
To maximise the daylighting of a building design, the building must be in correct alignment with the Sun. Sunshine entering the rooms in the autumn and winter, and in the morning is preferable. Sunshine at midday and in the afternoon between June and August is not desirable. Various strategies such as alignment of the building, form of window reveals, glazing bars, shading devices and high-level windows all provide control over the penetration of the Sun into the building.
The following diagrams represent the Sun path for the summer and winter solstices, along with the autumn and spring equinoxes. The diagrams are used to demonstrate the orientation of a proposed building.
A North-South building orientation receives sunshine on both sides but fewer windows on the north and south mean that minimal Sun will penetrate the building in November, December and January.
An East-West building is a suitable orientation for small flats. The living rooms and bedrooms can be positioned on the south, with stairs, bathroom, lobby, and utility areas to the north.
A North-West to South-East block suits larger flats with bedrooms and utility to the north-east and living rooms to the south-west.
A North-East to South-West building is well suited to 3 and 4 roomed flats with the living and bedrooms to the south-east and utility and subsidiary rooms to the north-west.
It is worth noting that light from above is brighter and as such the inclusion of roof lights are often preferable too. 100% of light from the sky will reach a roof light, whereas only 33% of the light from the sky will reach the windows at the side of a building. This can be controlled with angled roof lights, shading, up stands and so on.
Solar Gain
Solar gain occurs when the temperature of an internal space within a building increases due to the absorption of the Sun’s energy by the building fabric.
Generally speaking, we design to minimise solar gains, particularly during the summer months. However, during the colder months of the year we often look to exploit the solar gain to reduce heating loads.
The angle of the Sun plays a significant role in solar gain. The middle of the day is when the Sun is at its strongest, but it is also at its highest point, so often in the summer, the Sun hits a facade at a steep angle in the middle of the day and therefore the heat transfer remains relatively low. It is the time either side of the peak of the day where the angle of the Sun is lower, a more direct angle for impacting the facade and transferring a higher proportion of energy to the building. An exception to this is atria and roofs which face the Sun more directly at the middle of the day and are especially vulnerable to solar gain when the Sun is at its strongest.
To help control solar gain, shading systems are often applied to limit the amount of solar radiation that penetrates the facade. External shading devices are more effective than internal shading. Another strategy is the use of solar control glazing that restricts the amount of solar transmittance through the window.
Carefully planning the building orientation, window size, and placement during design can help you increase solar gain in winter while minimising unwanted gain in summer.
Materiality can also come in handy with regards to thermal mass, as concrete or stone floors and walls help absorb excess heat during the day and release it at night to regulate indoor temperatures.
Effective ventilation strategies either natural or mechanical are also important for removing excess heat from your buildings.
It is worth mentioning that natural Sun protection is also an option in low level buildings in the form of deciduous trees. The leafy tree will offer natural Sun protection in summer, but in winter will allow the Sun to pass through the tree letting warmth and light into the room.
With the increasing frequency of heatwaves and rising global temperatures, overheating from solar gain is an important design consideration.
Solar Shading
External shading can reduce the amount of energy required to cool a building during summer months. In comparison, internal shading is much less effective and not recommended since the solar energy has already passed through the facade and radiated back into the room.
Generally, in the northern hemisphere it is suggested that horizontal shading devices (such as overhangs or louvers) are best suited to south facing facades which help with the high angle Sun, while vertical shading systems (such as fins or screens) are best suited to east and west facades as they are able to deal with the lower angle Sun.
When designing shading systems, it is important to find a balance between providing the appropriate shading but maintaining good natural lighting levels within the building. Excessive shading can reduce daylight and increase the need for artificial lighting, while insufficient shading can lead to glare and overheating.
We also have a post on Passive Solar Design, that we think you may like:
Architecture Design Basics – Passive Solar Design
Glare
Glare can be described as the discomfort or impairment of vision caused by excessive range of brightness in the visual field. Causes of glare can range from bright skies seen through windows, direct views of bright lights, direct and indirect reflection from surfaces and unfavourable contrast in light density.
There are two main types of glare:
- Discomfort glare – which causes irritation, visual fatigue, or headaches but does not necessarily impair vision.
- Disability glare – which reduces the ability to see clearly, making it hard to distinguish objects, even if it does not always cause discomfort.
Glare is undesirable in any setting, as it can decrease occupant comfort, reduce concentration, and negatively impact performance especially in workplaces and learning environments.
- Some measures to take to avoid glare include:
- External shading devices
- Glare protection inside and outside
- Matte surfaces to avoid reflection
- Correct positioning of daylight enhancing lighting
- Diffused lighting fixtures or strategies
- Anti-glare window films, screens, or filters on monitors
- Adjustable lighting levels and dimmable fixtures
Helpful Links
Milutin Milankovitch
Daylighting Pattern Guide by New Buildings Institute
Sun Path Tools
Books
Here are some recommendations for further reading:
Neufert – Architects Data
Modern Construction Handbook – Andrew Watts
Environmental Science in Building – Randall McMullan
You Might Also Be Interested In…
We also have some helpful Sun path diagram cad blocks for London latitude 51 for you to download for free:
Free CAD Blocks – Sun Path Diagrams and North Points
Check out another interesting post on solar energy:
Solar Energy – Photovoltaic and Solar Thermal Strategies
We have loads of other incredible posts in our Building Fabric Series. Be sure to check them out.
Download the Guide!
Fill out the form below and we will send you this post as a PDF.
Conclusion
Designing with sunlight in mind is a thoughtful way to enhance building performance, elevate user comfort, and shape meaningful spaces. As shown in this post, tools like Sun path diagrams, site-specific solar data, and passive design principles provide the right foundation for making informed decisions early on in the design process.
We hope you found the information and diagrams in this post useful.
You can read all of the architecture and environment related posts here:
Architecture and the Environment
Thank you for reading!
Your Comments
What are your thoughts on solar gain? Do share your insights in the comments below.
Also, don’t forget to share this post with a friend.
Thank you :)
Author
Written by Emma Walshaw, Architectural Technologist and founder of First In Architecture and Detail Library. Emma has written a number of books about construction and architectural detailing.
I will love reading the book