Optimizing climatic comfort: Glass roofs and Atriums
Comfort modeling to optimize climate management systems for glass roofs and atria
EOLIOS is an expert in thermo-aerodynamic modelling for atria, halls and high-rise spaces.
- Analysis of solar radiation and heat gain
- 3D CFD modeling of indoor air flows
- Comfort assessment according to PMV and PPD
- Identification of hot zones and air stagnation
- Optimized air supply and mixing
- Integration of actual site climate scenarios
- Analysis of natural ventilation potential
- Help with HVAC sizing and control
- Validation of architectural choices and glass façades
EOLIOS is an expert in comfort in large glazed spaces. Our CFD simulations reveal areas of discomfort and optimize the design for a high-performance, controlled indoor climate.
Understanding the challenges of comfort in large spaces
Spaces of high architectural value but thermally complex
Atriums, reception halls and high-rise spaces play a central role in contemporary architecture. As showcases for tertiary, cultural or commercial buildings, they are distinguished by their generous volumes, their largely glazed walls and their direct link with the exterior. This transparency, a source of light and spatial quality, also becomes a major technical constraint. Solar gains, air mass stratification and the thermal inertia of structures constantly modify the balance of interior comfort.
Image of an atrium
In these open volumes, control of the indoor climate is based on a subtle dialogue between architectural design and flow physics. Warm air naturally tends to accumulate in the upper part of the building, while glass walls absorb and release solar radiation in rapid cycles. These effects, amplified by height and occupancy variability, create temperature gradients that are difficult to compensate for by a simple regulatory or static approach.
Dominant phenomena: radiation, stratification and inertia
Thermal comfort in a large hall depends on a combination of interdependent physical phenomena.
Solar radiation is the main source of incident energy. It passes through the glazing, transforms into heat on contact with interior surfaces, then radiates back to the occupants.
Thermal stratification, then, manifests itself in the superimposition of layers of air at different temperatures: warmer air rises, while denser, cooler air remains at the bottom, sometimes resulting in differences of several degrees between the ground and the canopy.
Finally, thethermal inertia of materials influences the reactivity of the building: solid walls or floors with high thermal capacity absorb variations, but can also release accumulated heat late in the day, prolonging episodes of discomfort.
Understanding these phenomena requires a dynamic approach, capable of reproducing the reciprocal exchanges between convection, conduction and radiation. It is precisely this complex interaction that EOLIOS seeks to model in order to predict the actual behavior of the building over time.
Comfort and energy performance objectives
Ensuring comfort in a high-rise space is not just a matter of maintaining an average temperature. It’s about creating a homogeneous, stable environment, where air velocities, radiant temperatures and vertical gradients remain within acceptable ranges for the majority of occupants. In these atypical volumes, the balance between comfort and energy performance is often fragile: excessive air mixing can alter the feeling of well-being, while undersizing the supply or cooling systems can lead to localized overheating.
The challenge is therefore twofold: to guarantee the perceived quality of the indoor climate while controlling the energy consumption of systems. Achieving this balance requires a detailed understanding of physical phenomena, a coupled approach to thermodynamics and aeraulics, and the use of simulation tools capable of reproducing the three-dimensional reality of comfort. This is the context in which EOLIOS deploys its expertise, integrating numerical analysis of the climatic behavior of large volumes right from the design stage.
The EOLIOS approach: modeling indoor climate
CFD simulation, a multi-physics analysis tool
Given the complexity of the phenomena that develop in an atrium or a high-rise hall, numerical simulation is today’s most effective tool for understanding and controlling indoor comfort. EOLIOS relies on Computational Fluid Dynamics (CFD ) to accurately reproduce the interactions between air, surfaces, heat and radiation.
These three-dimensional models simultaneously solve the conservation equations for mass, momentum and energy, providing a complete reading of the thermo-aerodynamic behavior of the volume.
This multi-physics approach makes it possible to analyze not only air velocities and pressures, but also heat transfer by convection and radiation. It thus offers a dynamic vision of how the building functions, highlighting stagnation zones, stratification phenomena or temperature imbalances between the different layers of air.
Thanks to the precision of the models developed, EOLIOS is able to reproduce the actual comfort conditions experienced, and deduce concrete optimization levers for air control, supply or distribution.
Taking solar radiation and climate scenarios into account
Solar gain is the main source of thermal imbalance in glazed areas. Their intensity, orientation and duration vary according to the season, the time of day and the transparency of the glazing.
To faithfully reproduce these conditions, EOLIOS integrates real meteorological data into its CFD models, combined with the position of the sun on the site under study. This approach simulates direct, diffuse and reflected radiation, taking into account the solar factor of glazing, shading of neighboring facades and the spectral behavior of materials.
The coupling of radiation and convection enables us to calculate the average radiant temperature, an essential parameter for assessing thermal sensations. Highly exposed areas under glass canopies or near facades can thus be identified and analyzed with precision.
Simulations are carried out for different extreme scenarios – hot summer, cold winter, mid-season – to ensure that the supply and cooling systems provide comfort under all conditions of use, even the most unfavorable.
This methodology gives EOLIOS studies a strong predictive value: it allows us to assess the behavior of the building in its climatic reality, and not in a fixed theoretical hypothesis.
Comfort assessment using PMV and PPD indices
Beyond temperatures or air speeds, the perception of comfort is based on a combination of physical and physiological factors. To objectify this perception, EOLIOS uses the standardized indicators PMV (Predicted Mean Vote) and PPD (Predicted Percentage of Dissatisfied), defined by ISO 7730.
The PMV quantifies the average thermal sensation of a group of occupants on a scale of -3 to +3, ranging from intense cold to excessive heat. The PPD, derived from PMV, estimates the percentage of people likely to be dissatisfied under simulated conditions. These indices take into account air temperature, mean radiant temperature, air speed, relative humidity, activity level and clothing.
By integrating these criteria into its CFD calculations, EOLIOS evaluates not only physical conditions but also their impact on human experience. This approach, centered on the occupants’ experience, makes it possible to precisely identify localized zones of discomfort and adjust system design to tend towards neutral comfort (PMV ≈ 0, PPD < 10%).
These analyses thus become an aid to design and regulation, ensuring that technical choices effectively reflect comfort and energy-saving objectives.
From diagnosis to climate strategy
Identify levers for action on diffusion and temperature
CFD analysis doesn’t just describe air flows: it reveals the precise mechanisms behind thermal imbalances. By visualizing the distribution of velocities, temperatures and vertical gradients, EOLIOS identifies recirculation zones, poorly mixed volumes or hot spots linked to localized solar gains.
Based on these observations, it becomes possible to formulate targeted action strategies, whether this involves adjusting the position of a supply air vent, modifying a diffusion angle or reviewing the regulation sequence. These optimizations, often minimal in material terms, can profoundly transform the quality of comfort in occupied zones.
In high-rise halls, air circulation control plays a central role. A subtle balance must be struck between speed and homogeneity: too rapid a flow generates a feeling of discomfort, while insufficient flow favors thermal stratification. Studies carried out by EOLIOS quantify these effects, enabling us to deduce the most appropriate settings for each configuration.
Integrating solar dynamics and energy regulation
Solar gain is a decisive variable in the thermal behaviour of large glazed areas. Their intensity and distribution vary according to the season, time of day and facade geometry, directly influencing the average radiant temperature and how occupants feel.
In its simulations, EOLIOS characterizes the effects of solar radiation in various representative operating regimes. By studying several contrasting situations – hot summer, cold winter, mid-season – the calculations highlight the areas most sensitive to solar gains and the thermal imbalances they can generate.
These results can then be used to make control recommendations, such as adapting the supply air flow rate, modulating the cooling floor or installing solar protection. The aim is not to simulate the control system in real time, but tohelp set its parameters and prioritize it, by defining the most effective levers for stabilizing comfort while limiting energy consumption.
In this way, CFD simulation becomes a decision-making tool for adjusting and sizing climatic systems, helping to ensure consistency between thermal comfort, solar gain and the building’s overall performance.
CFD simulation of the thermo-aerodynamic effects of an atrium
Design hybrid strategies: supply, exhaust and natural ventilation
Large interior volumes often feature such inertia that they can take advantage of natural phenomena to regulate their climate.
EOLIOS systematically studies the potential of natural ventilation and night-time free cooling, to assess the extent to which outside air can contribute to cooling or volume renewal. Simulations show how differences in air density between warm and cold layers can generate a natural thermal draught, which can be used to evacuate calories accumulated during the day.
This passive operating mode, combined with intelligent mechanical control, makes it possible to develop particularly effective hybrid strategies: natural ventilation at night, assisted blowing during the day, modulation of openings according to wind direction.
This integrated approach, at the crossroads of physics and architecture, aims to reduce energy dependency while guaranteeing constant air quality and thermal comfort.
Predictive comfort and simulation-aided design
Understanding before you build
Digital simulation allows us to observe a building before it is even built. By virtually reconstituting the geometry, materials and climatic conditions, EOLIOS can analyze the actual behavior of a high-rise space right from the design phase.
This predictive approach makes it possible toanticipate thermal and aeraulic phenomena likely to affect occupant comfort: heating under glass roofs, air stagnation zones, imbalances between sunny façades and shaded areas.
The studies carried out thus constitute a veritable virtual laboratory, in which architectural and technical choices can be tested, compared and optimized before implementation. This approach brings a concrete physical vision to decisions often guided by aesthetic or functional constraints, ensuring that the initial design remains compatible with lasting comfort of use.
Fine-tuning and making design more reliable
The results of CFD simulation are not fixed images: they serve to validate and adjust the design. Three-dimensional maps of temperature, velocity and pressure enable us to accurately assess the performance of the climate system, check the consistency of the blowing and detect areas for optimization.
These analyses help to make design choices more reliable by identifying the most sensitive parameters – nozzle orientation, air flow rates, supply air temperature, solar factor of glazing. Each configuration tested provides a more detailed understanding of the volume’s overall behavior, and guides sizing and balancing decisions.
This scientific approach, based on measurement and comparison, enhances the quality of projects and reduces the uncertainties associated with great heights or complex geometries. It guarantees that the building, once completed, will faithfully reproduce the expected performance.
Conceiving comfort as a performance criterion
In the EOLIOS approach, comfort is not just a consequence of the project: it becomes a central performance criterion. CFD studies make it possible to integrate notions of thermal comfort and radiation right from the sketch phase, assisting architects and HVAC engineers in their choices of spatial organization, air diffusion and façade transparency.
This collaborative approach favors integrated design, where physical constraints are translated into architectural opportunities. By assessing comfort conditions prior to construction, it becomes possible to steer the design towards solutions that are elegant, sober and efficient.
Finally, the use of digital simulation adds an essential dimension of predictability: it ensures that comfort conditions, thermal stability and energy performance will be achieved, whatever the building’s mode of operation. This mastery of the interior climate prior to construction is a decisive advantage for atrium and large hall projects, where the perception of space depends directly on the quality of the thermal and lighting ambience.
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Initially created in France, EOLIOS Ingénierie is the benchmark thermal and aeraulic simulation consultancy for data centers in Europe and worldwide. The company supports operators, designers and project owners at every stage in the life of a data center: design, optimization, renovation or extension.
By combining cutting-edge scientific expertise, state-of-the-art simulation tools and in-depth knowledge of the data center ecosystem, EOLIOS Ingénierie is a trusted partner for ensuring the availability, security and energy performance of IT infrastructures, while anticipating sustainability issues.
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