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Designing an exterior wall system that guarantees long-lasting integrity is crucial for architecture professionals. By understanding Gravity, Momentum, Surface Tension, Capillary Action, and Air Pressure Differences, which influence water movement through walls, designers can make informed decisions and ask the right questions during the detailing process. This article will guide you through these five steps, empowering you to create exterior wall systems that excel in durability, moisture management, and overall performance. Before discussing the empowering ways to ensure water tightness, let us discuss the five conceptual approaches that an architectural professional should be aware of when proceeding to detail any exterior wall system.
5 Conceptual Approaches to Water Tightness
1. Gravity
Gravity is the natural force that causes water to flow downward. If water accumulates on the exterior surface of a wall or if it enters through openings, gravity can cause it to flow vertically and potentially penetrate the wall assembly.
2. Momentum
Bulk water movement, aka momentum, refers to water movement in large quantities, such as during rainstorms or due to hydrostatic pressure. If there are breaches in the exterior wall system or inadequate drainage, bulk water can exert pressure and force its way through the wall assembly.
3. Surface Tension
Surface tension affects how water interacts with the exterior cladding material. It causes water to bead up and resist spreading out across the surface. In severe cases, it can adhere to the underside of a cladding material that is Ill-equipped to maintain its position outside the building. How the water tends to stick to building materials
4. Capillary Action
Capillary action is the ability of water to move through small spaces or gaps in a material, contrary to the force of gravity. If the wall materials, such as masonry or porous materials, have capillary pathways, water can be drawn upward against gravity, leading to moisture infiltration.
5. Air Pressure Differences, AKA Wind Currents
Differences in air pressure between the exterior and interior of a building can influence the movement of water vapor through the wall assembly. Air pressure differentials can force air and moisture into or out of the wall system, depending on the direction of the pressure gradient.
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Now that we have discussed the 5 Conceptual approaches to water tightness let us take a more analytical approach to challenging our detailing process when detailing exterior wall systems. Here are five steps to navigate this task.
Step 1: Assessing Gravity’s Impact
When detailing an exterior wall system, consider how gravity affects water movement. Ask yourself:
- How will gravity influence water drainage on the wall’s surface?
- Are there potential areas where water may accumulate or pool?
- How can you ensure proper sloping and surface runoff to prevent water infiltration?
Step 2: Confronting Bulk Water Movement
Bulk water movement poses a significant challenge to the integrity of exterior walls. To address it effectively, consider the following questions:
- How can you design an effective drainage system to handle heavy rain or hydrostatic pressure?
- Are there potential vulnerabilities in the wall assembly that may allow bulk water infiltration?
- What materials and techniques can mitigate the impact of bulk water movement?
Step 3: Conquering Capillary Action
Capillary Action can enable water to penetrate walls against the force of gravity. As you navigate this step, reflect on the following inquiries:
- Are there materials with capillary pathways that might contribute to moisture infiltration?
- How can you break capillary pathways or use capillary breaks to prevent water from moving vertically?
- What strategies can be employed to enhance the moisture resistance of the wall system?
Step 4: Managing Air Pressure Differences
Understanding air pressure differentials is crucial to prevent the migration of moisture-laden air through the wall system. Consider the following questions:
- How will pressure differences impact air and vapor movement?
- Can you identify potential areas where air or moisture might be forced into the wall assembly?
- What measures can equalize pressure and maintain the wall’s integrity?
Step 5: Addressing Vapor Diffusion
Vapor diffusion can lead to moisture-related issues within the wall assembly. While considering this step, keep the following questions in mind:
- How can you control and manage vapor diffusion through the wall system?
- What vapor retarders or barriers should be integrated to minimize moisture transfer?
- Can materials or construction techniques enhance the wall’s resistance to vapor diffusion?
In summation, design professionals can ensure maximum integrity and performance by following these five steps and posing these critical questions during the exterior wall system detailing process. Remember, each project has unique considerations, so adapt these steps to suit specific requirements. By actively engaging with these forces, you will create exterior wall systems that excel in durability, moisture management, and long-term functionality.
Remember that bulk water prevention is the most important thing above all else. Buildings get wet via roofing, window perimeters, window sills, and below-ground where the building meets the soil. Be sure to understand that most decisions are heavily dependent on the microclimate. Typical materials used to mitigate most water intrusion in the common areas are stones and highly effective materials like metals. By considering how buildings experience these common conditions and interact with building corners, window sills, and below-ground materials like Masnony brick, you can quickly reduce or find solutions for leaks from air and moisture.
Let’s examine a concrete case study and listen to architect Chris Benedict discuss the passive house techniques that resulted in her project, Knickerbocker Commons, being recognized as one of the affordable housing complexes constructed to meet “passive house” standards in the country.
Project Information & Tangible Case Study Knickerbocker Commons
| Project Type: | Affordable Residential Housing |
| Project Address: | 803 Knickerbocker Ave Brooklyn |
| Project Architect: | Chris Benedict R.A |
| Project cost: | $251 per square feet |
| Project Objective: | Housing initiatives for Knickerbocker Commons Passive Houses feature super-insulated and airtight structures. These residences employ various strategies, including strategically positioned windows and highly effective air circulation systems, to minimize energy expenses significantly. |
| Project Materials and energy savings: | Utilizing steel construction, a sculpted EIFS façade maximizes solar gain/shading, displacing the conventional heating system. Incorporating low-voltage equipment and water reuse systems results in an 80% reduction in energy costs compared to the average. |
| Project Size and Program: | Six Story Building 24 Rental Units Child Care Facility on the First Floor 5,000 Square feet of community facility space Total Square ft. 34,581 sq. ft. |
Project Photos
An Overview From the Architect
Check out this Webinar by Building Enclosure titled “Building Enclosure Control Layer Fundamentals” for more expansive information.
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JOURNAL
Le Chateau De Pierre is an Architecture and Interior Design Journal dedicated to sharing and exploring tips for emerging professionals and educating readers about great architecture and building design concepts. Our publication is designed to inspire and inform both new and experienced Interior designers, architects, and those interested in the field of architecture.
Resource Credit
Allen, E., & Iano, J. (1983). Fundamentals of Building Construction Materials and Methods (5th ed., p. 791 Figure 19.6). John Wiley & Sons.
