Wind comfort – Balconies
In a few words
EOLIOS contributed its technical expertise in the understanding and modeling of large-volume outdoor airflow in relation to the realization of CFD studies.
Wind comfort study for balconies
Year
2023
Customer
Location
France
Typology
Air & Wind
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Wind study on a block of flats
Before any new building is constructed involving individual outdoor spaces such as balconies, it is necessary to assess the thermal comfort of occupants on balconies and identify any problem areas. There are many ways to protect your balcony from the wind. The solution studied here is the use of sliding panels that do not completely enclose the balcony. Winds are colder and have a higher amplitude in winter. However, if the balcony is not fully enclosed during this period, it cannot be used due to the very low temperatures.
The aim of the wind study is to verify the wind speed profile on the building’s balconies, mainly those on the highest floors, and then to propose alternatives for optimizing the comfort of residents on their balconies.
Theclimatic analysis of the site is a fundamental step in any study of comfort on balconies. It allows us to determine the maximum speed reached over a year and the prevailing winds at the site using wind roses.
CFD studies have enabled us to visualize the various aeraulic phenomena for different wind orientations, which in turn has enabled us to optimize the geometry for the best possible wind turbine performance.
Comfort level on balconies
Before a building is constructed, the question of occupant comfort arises. Balconies are usually exposed to the wind. Depending on their amplitude, these winds can make balconies unoccupiable. It is therefore necessary to ensure that a good level of comfort on balconies is possible, at least in spring and summer when the weather is warm and sunny. Balconies are rated uncomfortable when wind speeds exceed 1 m/s.
Here are some orders of magnitude for V wind speeds:
- V < 0.2: speed in a closed space
- 0.2 < V < 0.5: velocity in a closed space when the window is opened, i.e. with an air current
- 0.4 < V < 1: breeze
- V > 1: when a fan is running
- V > 2: unpleasant wind
CFD simulation of wind around the building
CFD simulation enables us to control the specific aeraulic phenomena induced by the particular geometry of balconies, by studying the airflow around the building. Air velocities give an indication of the comfort level of inhabitants. Before any simulation, a 3D CFD model of the structure is produced. In this project, the interior of the building is not important, only the balconies have been modeled in detail.
Depending on the origin of the wind, air recirculation is sometimes observed at the rear of the building. As a result, some of the air arriving on the ground will be slowed down by friction, and will tend to flow upwards towards the building. Air then rushes into certain balconies, which can cause discomfort even when the wind is not blowing towards the building facade. This particular phenomenon must be taken into account before any building is constructed.
To determine the level of comfort on balconies, a local study of air speeds is carried out. It is possible to obtain the velocity vectors within each balcony. This makes it possible to observe areas of recirculation that are not disruptive, but also to detect areas of high speed and airflow.
Solutions to enhance residents' comfort
To maximize the comfort of the project’s inhabitants on their balconies, it is necessary to protect them from the wind. Artificial or plant-based windbreaks can be installed to limit wind speed in certain areas, break up turbulence or guide air flows. In this study, we have seen the effects of sliding panels as a solution against wind on balconies. Enclosed spaces and glazed railings are also possible solutions for this building project.
- Sliding panels
Installing a large number of sliding panels on balconies helps keep the wind out. The main feature of these panels is that they can be moved at will. This solution seems perfect for the study under consideration. The mobility of the panels means they can be opened in summer, allowing the balcony to be ventilated. This prevents overheating in balconies in summer. What’s more, in winter, the panels create a winter garden with a greenhouse effect in the balcony, thereby raising the temperature. This leads to a reduction in the use or power of the heating system during this period.
- Enclosed spaces
The ideal solution for protection from the wind is to create an enclosed space completely isolated from the outside. Being completely isolated from external flows, you don’t feel the wind. These enclosed spaces have their drawbacks. In fact, they can’t be opened to the outside, which leads to overheating in summer. What’s more, people feel differently on a veranda than on a balcony. Enclosed spaces don’t give you the feeling of being outside.
Other solutions could have been envisaged, such as railings, fixed fences, awnings or windbreaks.
