How Breathable Should Facades Be? Exploring Permeability and Impermeability in Building Envelopes
The main role of architecture is to create structures that protect us from the environment and create spaces that are safe and comfortable for all types of needs and activities. By providing shelter, architecture also shapes the way people interact with their surroundings. Building technologies of the past rarely managed, however, to create a complete separation between us and the outside world.
While impermeability was a desired outcome, the porous building materials available always allowed some water, wind, or outside particles to leak into the interior spaces. In contrast, modern technologies now allow for almost completely impermeable building envelopes, allowing for complete separation between indoors and outdoors, thus relying on engineered systems to regulate temperature, airflow, or humidity. This article explores the differences between these two contrasting approaches, exploring how building facades are equipped to regulate indoor comfort and its environmental impact.
Often in the case of vernacular architecture well-adapted to local climates, this presence of natural elements in our built spaces is exploited and manipulated to become a positive factor that contributes to the comfort of said spaces. One such example is natural ventilation, a passive strategy that uses winds and cross-ventilation to bring fresh outdoor air inside, using it to regulate temperatures, humidity, and air movement.
Related Article
Balancing Function and Aesthetics: Incorporating Natural Light and Ventilation in Facades
Even in the absence of such mitigating factors, historical structures built with natural materials such as wood, stone, and adobe tend to be more permeable, allowing water to enter the structure to some degree. This aspect must be taken into consideration especially when rehabilitating historical facades, as adding modern impermeable layers can change the initial balance, running the risk of trapping water inside certain substructures, thus leading to accelerated degradations.
Permeable building envelopes have, however, a range of associated risks, including moisture infiltration, mold growth, and structural degradation. In the search for more resilient strategies, technological advancements allowed for more and more impermeable building designs. Since the rise of modern architectural movements, the predominant design technologies favored impermeable building envelopes that create more stable interior conditions, thus reducing the resources needed to create the desired level of comfort.
This had a significant impact on the energy efficiency of buildings, as reduced thermic and chemical exchanges meant fewer resources needed to create the desired level of comfort. At the opposite end of the traditional envelopes, there are structures following standards such as Passivhaus, which prompt as complete separation as possible. New and perfected building techniques such as advanced insulation materials and airtight construction techniques allow for this type of separation.
In the last few years, passive house standards have developed into an international currency for energy-efficient construction. The system requires advanced thermal performance and air-tight construction to minimize unnecessary loss or gain of heat. To control air quality, moisture, and temperature, they rely on engineered mechanical systems such as heat recovery ventilation. Together with on-site renewable energy production, this has enabled the building of “positive energy” buildings, producing more energy than they consume.
Such a complex and tight-knit system does come, however, with several challenges. In addition to the high initial costs, a meticulous building process, and constant maintenance, the mechanical systems can be somewhat difficult to adapt to occupant behavior and unaccounted-for climate fluctuations. The dependence on building technologies also raises concerns about the long-term reliability and compatibility with future innovations.
As technologies continue to advance, a balance between permeability and impermeability seems to take shape as an advantageous alternative, integrating passive strategies with active systems to create dynamic, responsive buildings. Beyond reducing energy consumption, buildings must provide healthy, inviting spaces that enhance occupants’ quality of life. Passive design strategies such as ample daylighting, natural ventilation, and thermal comfort play a crucial role in promoting occupant health, productivity, and satisfaction. In addition, integrating biophilic design principles, such as incorporating natural materials and vegetation, further fosters a connection with nature and enhances the overall indoor environment.
Among these hybrid approaches, one example is the integration of mixed-mode ventilation systems, which leverage natural airflow supplemented by mechanical ventilation to adapt to varying environmental conditions. Adaptive facades, incorporating movable elements and responsive technologies, further enhance building performance by modulating solar heat gain and daylight penetration. Hybrid designs may also incorporate thermal mass materials, such as concrete, stone, or rammed earth to optimize temperature fluctuations and reduce heating and cooling loads.
Additionally, hybrid passive solar designs combine passive solar principles, such as orientation, shading, and glazing ratios, with supplemental mechanical systems. Buildings using this often feature insulated glazing and thermal mass elements to maximize solar heat gain during the winter, supplemented by mechanical ventilation and shading controls to mitigate overheating in summer. Drawing inspiration from vernacular architecture, designers are also embracing locally sourced materials, traditional craftsmanship, and bioclimatic design solutions, thus contributing to the local culture and heritage while minimizing the carbon footprint.
It is undeniable that passive house standards represent a significant advancement in sustainable building design, offering a new level of energy efficiency and environmental performance. However, to realize their full potential, it’s essential to adopt a balanced approach that considers the complex interplay between permeability and impermeability, sustainability impact, occupant comfort, and market acceptance. Taking a page out of traditional and vernacular building techniques has the potential to further enhance both the environmental footprint and comfort and the health, satisfaction, and well-being of occupants.
This article is part of the ArchDaily Topics: Building Envelope, proudly presented by Vitrocsa, the original minimalist windows since 1992.
Vitrocsa designed the original minimalist window systems, a unique range of solutions, dedicated to the frameless window boasting the narrowest sightline barriers in the world: Manufactured in line with the renowned Swiss Made tradition for 30 years, Vitrocsa’s systems “are the product of unrivaled expertise and a constant quest for innovation, enabling us to meet the most ambitious architectural visions.”
Every month we explore a topic in-depth through articles, interviews, news, and architecture projects. We invite you to learn more about our ArchDaily Topics. And, as always, at ArchDaily we welcome the contributions of our readers; if you want to submit an article or project, contact us.
