Fabric vs Glass vs Translucent Panels
What should you cover your building with if you want natural daylight? The options are many with a variety of costs, benefits, and long-term performance issues.
- Fabric is lightweight, comes in a variety of materials to address a number of surface configurations. The overall weight of the surface is always less than 5psf and great expanses of surface can be made with a few seams. Fabric and textiles can perform a number of features that allow for both water resistant services and breathable meshes. The material and application is always key to the performance. Deciding if you want an interior or exterior space also helps you select your fabric material. Most people think of fabric for canopies, entrances, or umbrellas. Some of the most advanced architectural structures utilized fabric, foil or a textile. Fabric’s apparent lightweight comes with a price and requires that it be planned and implemented from the beginning. The price is structure. Tension structures require a rigid frame. Just like a tennis racquet, the strength comes from the support. Fabric clad structures, on the other hand, just need structure to define the shape and need to be rigid to maintain the shape and keep the fabric in its desired form. Fabric produces nice diffuse lighting and provides a surface for nighttime lighting effects. The acoustic performance of fabric depends on so many things, the most critical being surface shape and material. Thermal performance depends mostly on material selection and the interior environment of the space. Other translucent options include foils like ETFE.
- Translucent panels are a sandwich structure that utilizes an inner and outer panel manufactured from plastics. There are also honeycomb structures, extruded planks and insulated panels using nano-gel. The interior superstructure is often aluminum and the panels are pre-manufactured to a variety of sizes and configurations based on span, loading, and desired performance. These products have been utilized mostly in secondary vision applications, such as clerestory, skylights, saw tooth roof structures, and privacy walls. The panel system is also lightweight, modular and supported off of structure if the span exceeds the panel’s capability. Panels are usually 4’x8’ in dimension or smaller depending on the span and loading. A variety of colors and performance characteristics for envelope applications are worked out with the supplier or manufacturer. The advantage is that they are easy to design with, spec and install. The most tauted disadvantage has to do with long-term discoloration or ‘yellowing’ of panels in direct sunlight. This has to do with the chemistry of the plastics and is an issue of performance and safety. Efforts have been made to address this issue. However, because of the cost structure of these panels, it is often cheaper to replace these panels than spend a lot of money to make sure they don’t discolor. The time line for replacement depends upon exposure and the panel materials chosen. The panels could need to be replaced as early as 5-7yrs or as late as 10-15yrs. The translucent panels are great for planar applications and low curvature profiles. They provide nice passive lighting and add an architectural lighting surface for nighttime applications.
- Glass is everywhere. Glass has experienced a renaissance in the many applications that are found for this transparent structural liquid. Glass is technically a liquid based on its chemistry and long term performance characteristics. Don’t worry, your building is not going to look like it’s melting. It takes hundreds of years. Glass comes in planar elements, can be rolled, formed, laminated, coated, and colorized. It really is a robust material. Glass performs best when it is in compression. So don’t pull too hard on glass or it will splinter, shatter or fracture. It may seem that glass isn’t good at all based on the previous statements. I just wanted to let you know that glass is not invulnerable. Glass has just been engineered and supported by other materials and strategies to address its weaknesses. Glass provides the ultimate visibility for building barriers, envelopes, and protection. Glass sometimes provides too much tranparency. So strategies, such as fritting, coatings, and printing patterns on to glass surfaces provide the appropriate levels of transparency. There are also electro chromatic films (privacy glass) that switch on and off with a current of electricity. Glass provides various levels of thermal performance depending on the layering and if the system is designed from IGUs. Glass weighs anywhere from 5psf all the way up to 50psf for blast resistant glass. Glass has great long-term performance characteristics. The considerations for its continued visual performance are cracking/chipping from impacts, etching from standing water, and scratches from improper use. Glass is often used in conjunction with other shading systems to address year-round solar exposure to address heat gain, glare, and solar angle. Glass does a great job as a cladding, and as structure. Glass can be custom manufactured to meet a variety of profiles and support conditions.
In the end, which is best? The answer lies in the design. Location is also key. So make an informed decision. Ask someone who specializes in these systems and the structures that support them. The cost of not knowing which is right for you can bring unexpected suprises later if you need change you mind.
