A Review of the Impacts of Façade Features on UNI and Occupants’ Perceptual Reactions in Apartment Housing

Imagine living in a city where the air feels heavy with the roar of traffic, construction, and the hum of daily life. This constant din is not just an annoyance; it creates what researchers call "Urban Noise Islands," pockets of intense sound trapped within the concrete canyons of a city. When these noise levels become too high, people instinctively retreat indoors, closing their windows to find peace. This simple act of closing up tight, however, has a hidden cost. Without fresh air flowing through open windows, residents must rely on air conditioning to stay cool, which in turn pumps more heat into the city streets, making the environment even hotter and driving energy bills higher. The question facing architects and city planners is whether the design of a building's outer skin—the façade—can break this cycle. Can the shape, material, and details of an apartment building's exterior silence the noise enough to let people keep their windows open, thereby saving energy and improving health?

A team of researchers from Islamic Azad University set out to answer this by reviewing decades of scientific studies to see how the architecture of apartment buildings interacts with urban noise and the people living inside them. They did not conduct new experiments in a lab; instead, they gathered and analyzed findings from thirty-six different studies published between 2003 and 2026. Their goal was to understand the specific features of a building's face that could either amplify or dampen the noise coming from the street, and how those changes affect the well-being of the residents. They found that the answer lies in four main areas: the three-dimensional shape of the building, the materials used on its surface, added elements like screens or plants, and the quality of the surrounding neighborhood.

The researchers discovered that the geometry of a building plays a massive role in how sound behaves. A flat, smooth wall acts like a mirror for sound waves, bouncing traffic noise back into the street or toward neighboring buildings. However, when a façade is broken up with balconies, recessed windows, or angled surfaces, it scatters the sound, breaking up the noise waves and lowering their intensity. For instance, studies showed that adding an inclined ceiling to a balcony or using triangular shapes on the upper floors could reduce noise levels by up to 16 decibels in some cases. Even the placement of windows matters; moving an opening slightly or adding louvers can block the direct path of sound while still allowing air to flow through. One study noted that a simple change in the angle of an overhanging roof could reduce noise by as much as 15 decibels on higher floors, proving that small architectural tweaks can have a loud impact.

Beyond shape, the materials covering the building are equally critical. The review highlighted that hard, reflective surfaces like glass, stone, and metal tend to bounce sound around, keeping noise levels high. In contrast, porous materials that absorb sound, such as specialized foams or textured cladding, can soak up the noise energy. The researchers noted that using sound-absorbing materials on a façade could lower noise levels by up to 10 decibels compared to reflective ones. They also looked at "add-on" elements, such as green walls, vegetation on roofs, and acoustic screens. These features act as natural barriers, with green walls and inclined screens capable of reflecting sound away from the building or absorbing it entirely. One study found that solar panels placed on green roofs could reduce sound pressure by 5 decibels, showing that functional additions can serve a dual purpose.

The influence of the neighborhood itself cannot be ignored. The researchers found that the layout of the streets, the width of the roads, and the presence of green spaces or other buildings all interact with the apartment façade. A wide road with fast-moving traffic creates a different noise environment than a narrow, tree-lined street. Interestingly, the study suggested that placing noise-insensitive buildings, like offices or green spaces, between a noisy road and residential apartments can act as a buffer, protecting the homes without the need for expensive walls. The team emphasized that a building does not exist in a vacuum; its ability to mitigate noise depends heavily on how it fits into the surrounding urban fabric.

The ultimate goal of these architectural adjustments is to improve the lives of the people inside. The review connected the dots between noise, behavior, and energy use. When residents are exposed to high noise levels, they suffer from stress, sleeplessness, and anxiety, leading them to stay indoors with windows shut. This behavior forces a heavy reliance on air conditioning, which increases energy consumption and contributes to the "Urban Heat Island" effect, where cities become significantly hotter than the surrounding countryside. By designing façades that lower noise levels, architects can encourage residents to open their windows and use natural ventilation. The researchers cited findings suggesting that a 10-decibel reduction in noise could allow for a 45 percent decrease in cooling energy needs. This creates a positive feedback loop: less noise means more fresh air, which means less energy use and a cooler city.

While the review provides a clear roadmap for how building design can mitigate noise, the authors caution that these solutions are not yet standard practice in all architectural projects. They noted that while the science of sound reflection and absorption is well understood, translating these principles into everyday building designs requires more attention. The study suggests that future work should focus on field tests to see how these designs perform in real-world conditions, moving beyond simulations to actual buildings. For now, the evidence is strong: the way an apartment building looks and is built is not just a matter of aesthetics. It is a powerful tool that can quiet the city, protect the health of its residents, and reduce the energy needed to keep them comfortable. By treating the façade as a functional shield against noise, cities can begin to solve the complex puzzle of urban living, turning concrete shells into spaces that breathe.