Designing with the sun

The sun influences continuously and dynamically It affects the thermal balance of buildings, well beyond what external temperatures indicate. Its effect varies over time and space, interacting with surfaces, materials, and occupants.

Designing with the sun means governing a complex physical phenomenon that directly affects the comfort of the environments in their actual conditions of use and, in this context, orientation plays a primary design role, as it is capable of determining the distribution of radiant loads and the microclimatic stability of the spaces.

Facades, sections and construction details all operate as climate regulation tools: screening, depth of openings, mass and ventilation contribute to defining an architecture capable of maintaining a thermal balance that creates consistent comfort conditions over time, before and beyond the support of the plants.

Geometry of the Sun: Orientation, Solar Altitudes, Critical Hours

Solar design starts from understanding the geometry of its apparent motion, described by the azimuth and elevation angles, which vary depending on the season, time of day and geographical location.

This variability determines how radiation impacts the surfaces of the building, influencing direction, intensity and duration of solar gains and directly affecting the thermal balance of internal spaces.

Il radiation behavior It varies significantly based on the orientation of the facades. Some exposures receive radiation that is more easily controlled through geometric devices, while others are affected by low-level solar gains, often coinciding with the hours of use of the rooms; this makes it more difficult to contain radiant loads and increases the risk of overheating.

In this context, orientation becomes a design choice that affects the distribution of transparency, the depth of the rooms, and the quality of perceived comfort.

The design of the facade and the section allows to control these effects: projections, sunblind, lodges and setbacks operate as climate control devices, as they select the portions of visible sky and continuously modulate the solar contribution throughout the day and the seasons. Learn more here path of the sun.

Comfort and thermal balance: beyond air temperature

Thermal comfort cannot be reduced to air temperature alone or to the control of a setpoint: it is the result of a complex balance between the human body and the surrounding environment, in which various physical factors intervene, such as temperature and air movement, relative humidity and, crucially, mean radiant temperature and radiant asymmetries.

In well-insulated buildings, these latter aspects become central, since the internal surfaces and windows exposed to the sun contribute significantly to the thermal perception.

An irradiated glass surface can behave like a hot body, increasing the local radiant temperature, while direct solar radiation can hit the occupants, causing discomfort even in apparently comfortable air conditions.

For this reason, the most advanced comfort models explicitly consider the radiative contribution, distinguishing between direct and diffuse share and evaluating the effect of the shielding.

This leads to a shift in design scale: not just designing the space, but the body's microclimate within it. In operational terms, this implies:

• Avoid fixed locations exposed direct radiation during critical hours;
• Designing screens as tools irradiation control on surfaces and people;
• Interpret the comfort as a dynamic condition, variable over the seasons.

Facades and windows: balancing light, energy efficiency, and thermal stability

The facade works as a system of exchanges between inside and outside, in which the window plays a decisive role in the energy performance and comfort of the rooms.

In fact, several mechanisms are activated through the window frame – thermal transmission, solar gain, airtightness and natural lighting – which act simultaneously and interdependently.

The quality of the project does not therefore depend on a single performance parameter, but on the ability to manage these factors in a homogeneous and integrated manner.

In this sense, it is not only the quantity of glass surface that determines the result, but also its distribution and design: facades with the same percentage of transparency can behave very differently depending on the position, continuity of the openings and the full/empty ratio.

Also the window depth plays a significant design role: recesses, splays, jambs and sills generate self-shading effects and contribute to glare control.

A clear consequence follows: before increasing transparency for spatial or perceptual reasons, it is necessary design solar gain control, so that the facade does not become a source of thermal instability.

Shielding: "optical" devices before energy ones

Le solar shading they are often perceived as mere accessory elements, but they are actually real architectural components capable of regulating the relationship between building, sky and sun, and of combining solar control and spatial quality.

Their primary function is optical in nature: they select portions of the visible sky and intercept radiation before it enters internal spaces, directly influencing their thermal equilibrium and behavior.

Effective shading reduces solar gains and summer load peaks, making an important contribution to microclimatic stability of environments; but not all sunscreens are the same.

External solutions are generally more effective, as they block radiation before it passes through the glass, while internal ones improve visual comfort, as they intervene once the heat has already partially penetrated.

Solar Designs. ENI SpA Building – Energy Revolution at EUR
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From a design point of view, the shields translate into measurable geometries:

• Horizontal overhangs for the high sun;
• Vertical sunshades for low sun;
• Adjustable slats for adaptive control;
• Morphological solutions integrated into the shape of the building.

Also read: "Bioclimatic architecture: principles for good design"

Inertia, ventilation and layout: thermal balance throughout the day

If orientation and screening regulate the amount of radiation entering the building, thermal inertia and ventilation determine its behavior over time.

The thermal mass, made of materials with a high accumulation capacity, absorbs excess heat and releases it gradually, helping to dampen peaks and stabilize the internal temperature trend. This effect is especially effective when the mass is integrated into a coherent solar collection and control strategy.

In this context, layout plays a crucial role. The distribution of spaces and massive surfaces directly influences the quality of comfort and thermal perception.

In particular, it is useful:

• Place the mass in areas that receive controlled solar gains, avoiding radiant asymmetries;
• Separate the rooms based on functions and times of use, inserting buffer spaces between exposed facades and sensitive rooms;
• use the natural ventilation, especially at night, as a tool for dissipating accumulated heat.

The result of a good “solar design” is a building with reduced fluctuations in operating and radiant temperatures, which is therefore more stable and comfortable under real-world conditions of use.

Conclusions

Designing for the sun means building a dynamic thermal balance between geometry, matter and use of spacesOrientation, façade, shading, massing, and ventilation act as parts of a single system, capable of managing solar radiation and transforming it from a critical factor into a design resource.

The quality of architecture emerges when the control of solar gains translates into microclimatic stability and real comfort in the living hours of the environments, reducing dependence on downstream corrective solutions.

Learning to manage the contribution of the sun in architecture means developing a transversal skill that runs through architectural design and measures its technical and cultural awareness.