High-Pressure Laminates in Rainscreen Facade

A highly durable solution with design freedom and flexibility
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Sponsored by Trespa North America Ltd.
By Peter J. Arsenault, FAIA, NCARB, LEED AP

Design Characteristics of HPL Panels

Architects looking for a cladding material that provides ultimate design freedom for facades can find it in HPL panels used on a rainscreen system. This can be true if the design intent is to make a dramatic statement, blend the building in with its surroundings, or just about any approach in between. The nature of this HPL homogenous product means that it is very economical both to purchase and install, thus removing budget limitations on building design that can come with other materials.

Based on these fundamental characteristics, manufacturers of HPL facade cladding panels offer a very wide and broad palette of materials that architects can select from, mix, match, or otherwise work with. The common design choices are summarized as follows.

  • Wide color range: HPL panel color is determined primarily by the selection of the decorative layer on the panels. Hence, manufacturers can readily offer a full range of choices in a broad color spectrum that allows for creative expression and even inspirational design. Since there are so many standard colors available, it can be quite economical to use multiple colors on a facade design and create quite sophisticated looks as a result. For large projects, it is even possible and justifiable to work with a manufacturer to create specific project colors for more expressive and individualized facades.
  • Single- or double-sided color: Since multiple layers are used to create the finished product, it is possible to choose HPL panels that have a finish color on only one side or both sides. Further, if both sides are selected, the colors could be different on each side, as may be appropriate to the needs of a project.
  • Multiple finish styles: HPL panels are available in a variety of standard finish styles. In addition to uniform colors that are characteristically solid and consistent, there are other popular facade options too. Some finishes simulate the look and sleek characteristics of raw or finished popular metals used on facades but with much less weight and expense. Similarly, panels with the appearance of wood grain or stone offer a natural look with different stained wood grain or stone texture options. Metallic finishes bring some unique capabilities by reflecting light in predictable but intriguing patterns that offer a very unique look.
  • Variety of textures: The manufacturing process allows for a choice of surface sheens, including a range from subtle matte finishes to various degrees of gloss. It is also possible for the surface to mimic the texture of rock finishes or emulate stained wood surface textures.
  • Multiple panel sizes: Sometimes the design of a facade can be limited by the size of the cladding products available. HPL panels are available in a range of sizes, with at least one manufacturer offering four different standard sizes that are intended to work with common facade dimensioning. This allows for the efficient integration of the HPL panels into architectural designs with greater control over seams, geometric patterns, and final designs. Further, since the material can be easily cut in a fabrication shop or on-site with common carpentry tools, custom sizes and shapes are easy to achieve. In those cases, the most efficient and economical size can be selected to cut multiple custom shapes so as to minimize waste.
  • Different panel thicknesses: Like any sheet material, the strength and rigidity of HPL increases as the thickness of the panel increases. In some facade designs, the size and span of the panel between supports is large, suggesting that a thicker panel is needed to remain rigid. In other cases where the panel span is shorter, the thickness may be able to be reduced to take full advantage of the possible weight and cost savings.
  • Perforations: Not all facades need all of the cladding to be solid. Rather, some perforation may be desired for design aesthetics, enhanced airflow, or other reasons. Perforated HPL panels can be used in this case with the perforations following a standard pattern or in some cases as a custom design. The size of the perforation can range from very small to quite large.
  • Unique panel shapes: There is no reason that HPL panels need to be limited to rectangular shapes. Rather, their ease of workability and the variety of size, thickness, and other features means that unique geometric or other shapes can be designed, fabricated, and installed to create dynamic, custom, and unique building facades.
  • Multiple uses: The general opaque wall areas are usually the focus of facade design, but the versatility of HPL panels means that they are not restricted to just facade surfaces but can also be used in ancillary or visually supporting locations. Such applications can include soffits, canopies, and sunscreens as well as balcony enclosure panels. However, please note that they are not suitable for floor or roof surfaces.
  • Renovation projects: All of the design attributes of HPL panels can clearly benefit new construction, but they are also ideal for renovation projects. In this case, the light weight and thin material can allow direct application over existing facades, thus avoiding unnecessary selective demolition costs. Recladding existing buildings can also transform them from looking outdated and worn into a new, vibrant, and more current design.

With all of these different design capabilities, it is easy to see why architects can enjoy great design freedom when using HPL cladding panels to create notable and appealing building facades.

Images courtesy of Trespa North America Ltd.

The range of design characteristics of HPL panels allows for complete design freedom when creating building facades.

Performance Characteristics of HPL Panels

It is always good to find and use a cladding product that looks great and provides for a lot of design freedom, but in addition, it needs to perform as intended. In this regard, HPL panels bring a substantial collection of beneficial properties. It is important to recognize that all the performance characteristics discussed below can be verified by manufacturers or independent third parties based on specific laboratory testing for each. There are also plenty of building projects that have been in place for decades that exhibit each of these characteristics and can be verified as well.

  • Weather resistance: The dense makeup of HPL panels combined with the clear, protective outer layers means that weather does not have much impact on the material. It readily sheds water, is not bothered by wind, and even long periods of bright sun exposure do not impact the panels.
  • Harsh climate tolerance: Project locations with particularly harsh conditions, such as saltwater spray, intense heat, or severe weather events, are suitable locations for HPL cladding panels. Panels are designed to withstand exterior elements.
  • Inherent panel strength: The laminated makeup of the HPL and the combination of resins used, all contribute to the overall strength and rigidity of the panels. Even in lesser thicknesses, the density and integrity of the material is high. This means that it can tolerate high winds and other imposed loading in addition to carrying its own weight. The thickness can be increased as needed to suit local conditions with increased strength. Relatedly, it should be noted that the strength and integrity of the panel is not compromised when the material is cut. Rather, simply shaping the cut edges, much the same way as shaping cut hardwood, maintains the integrity of the product without fear of moisture seeping into the product from the cut edges. The phenolic resins in the layers resist this.
  • UV resistance: HPL panels with clear, protective layers have consistently demonstrated excellent resistance to ultraviolet (UV) rays from sunlight. This is a particular advantage since many other materials do not tolerate UV light as well and can degrade over time.
  • Color stability: Accelerated and real-time testing of HPL panels and samples has shown that the colors remain remarkably stable over time. In many cases, minimal fading or other changes to the panel have occurred. Manufacturers understandably relish in taking new pieces of a product, placing them next to a facade that has been in place for years, and straining to see any difference between the old and new. This is not only a benefit for the original facades, but it also makes additions or renovations easier since the new panels will likely not be visually discernable from the original, older panels.
  • Longevity: With the inherent resistance capabilities and color-retention qualities of HPL panels, it should be no surprise that they provide excellent long-term performance. Longer service life means operational savings for the building owner as well as some assurance that the building will continue to look good over time.
  • Resistance to acid rain: The same things that make the surface highly resistant to weather and other conditions can also make it quite resistant to acid rain. The dense material and impenetrable surfaces provide a nonreactive surface that deflects away acid rain that might otherwise show up on a different facade material.
  • Low maintenance: All of these preceding performance characteristics also mean that HPL panels are indeed easy to clean. The dense, resistant surface means that dirt, grime, graffiti, and other surface issues are all easily cleaned. The owner gets the benefit of this low maintenance characteristic, which is typically anticipated to last over the entire life of the building.

A big part of the success behind the performance of HPL panels on building facades has to do with the way they are manufactured. At least one manufacturer uses an electron beam curing process to assure the overall integrity and long-lasting nature of the decorative layer. For the proper protection and use as an exterior cladding product, the outermost layer can also be formulated specifically as an environmental barrier coating. It is always recommended to compare products between manufacturers and verify the unique processes used that directly impact performance results.

Images courtesy of Trespa North America Ltd.

HPL surfaces are remarkably color stable and UV resistant, as shown by comparing new panel pieces against those that have been on this building in the Netherlands for 24 years.

HPL Cladding Support and Installation

The design of a rainscreen is the first step in a successful building facade that is necessarily followed by a professional installation. Understanding the support and installation process informs the design and influences the overall performance of a project.

Support Systems

While the HPL panels are the visible pieces that receive a lot of design attention, the underlying support systems are the components that make the whole system work. Selecting and designing the proper support configuration helps assure that the cladding is held properly in place, creates the appropriately sized drainage space, and minimizes interruption of continuous insulation and WRBs. It is also the system that allows HPL panels to be installed vertically, horizontally, or at an angle to suit different project designs.

The support system for HPL panels most commonly consists of specially fabricated aluminum channels or angles. The channels are typically installed vertically although other variations are possible. The preferred approach is for the channels to be secured by using separate clips or supports that penetrate minimally through the continuous insulation into suitable building structural members. Other approaches are possible, but it is important that the selected system is compatible with the cladding so that the cladding and support systems work together.

Photos courtesy of Trespa North America Ltd.

HPL panel installation is very straightforward using conventional carpentry tools and techniques.

 

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Originally published in February 2021

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