Advances in curtain walls: Fibre-reinforced polymer technology

by arslan_ahmed | March 8, 2024 9:27 pm

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By Greg Koch

As energy codes and sustainability standards continue to drive industry innovation, specifiers can now choose curtain wall systems that waste significantly less energy than their predecessors.

Some manufacturers are using fibre-reinforced polymer (FRP) technology to create curtain wall components, reinforcements, and pressure plates that can be incorporated into the hollow chambers of aluminum frames to significantly bolster the system’s overall energy performance.

During the energy crisis in the 1970s and 1980s, it was discovered that a thermal break in the middle of an aluminum frame could deliver much greater thermal efficiency. Since then, this technology has progressed, but very slowly. From polyamide 6.6 to today’s polyester and polyurethane thermal blocks, and new part innovations, the industry is beginning to develop more ways to use FRP technology. It has been a very slow process, but material developments in this sphere are now gaining in popularity.

FRP materials can be manufactured with the same strength and stiffness as metal, and they exhibit almost zero creep under structural loads. FRP components possess a flexural modulus of up to 51,710 MPa (7,500 ksi), versus the flexural modulus of aluminum, which is 68,947 MPa (10,000 ksi). This difference of 25 per cent allows FRP materials to have 25 per cent more relevant cross-sectional area to match the strength of aluminum. This also provides them with higher resistance to linear compression, screw pull-out, abrasion, cracking, splitting, and flexural fatigue. They are also unaffected by environmental conditions such as salt air/water corrosion, water absorption, extreme hot/cold climates, and common chemicals. The result is a material as strong as aluminum yet boasting better environmental and thermal properties.

In terms of thermal efficiency, FRP materials can boast up to 900 times the thermal effectiveness of aluminum.² This translates to savings for large-scale commercial structures. It helps structures make the most use of the energy being used to moderate their interior temperatures by not allowing nearly as much heat loss or gain to occur through the building envelope.

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Component options

There are several key areas of the curtain wall framing where FRP materials can be used as a solution.

Pressure plates

Pressure plates are fastened to the outside of mullions in a curtain wall system to hold the glass in place. FRP pressure plates can be custom designed to fit into a fabricator or original equipment manufacturer’s (OEM’s) proprietary fenestration system.

Commercial projects using FRP pressure plates will notice significant thermal benefits because of the material’s low thermal conductivity rate, especially when compared to aluminum. In addition to outperforming aluminum, FRP pressure plates provide more compressive and flexural strength head-to-head against other materials often used for this purpose, including plastics or polyamide.

Structural thermal struts

Structural thermal struts are used for a thermal break between windows, doors, and curtain walls and can be created from FRP materials to deliver a solution that is better than old, outmoded options. FRP struts replace pour and de-bridge thermal fills and offer added structural strength, flexibility, and faster assembly for workers. They also perform well with polyurethane adhesives.

Additional curtain wall components

In a single, custom solution, FRP curtain wall components can be used by specifiers to meet the needs of an array of architectural designs for structural support and the energy efficiency of the overall building and curtain wall system they are used on.

FRP components also remain impermeable to virtually any reasonable natural heat or cold with temperature resistance ranging from -40 C (-40 F) to more than 93 C (200 F) for suitability in any climate in Canada or the U.S.

FRP curtain wall components can work with both primary types of curtain wall construction methods/designs: unitized or stick-built systems.

There are no current standards for using fibreglass in architectural aluminum, making it more difficult to specify. Curtain wall designers are beginning to see that using FRP materials in their systems can significantly improve the thermal performance of their designs. However, most designers are still not using these products. The responsibility is on FRP manufacturers to promote the technology to designers and architects. Recently, there are more large curtain wall manufacturers adding these products to their designs. In fact, some manufacturers have created entire window walls out of the material.

According to the Fenestration & Glazing Industry Alliance (FGIA),¹ curtain wall sightlines are typically 57.15- to 76.3-mm (2.25- to 3-in.) wide, with a system depth of approximately 152.4 to 254 mm (6 to 10 in.). Regardless of which construction type or dimensions are selected for the curtain wall, FRP manufacturers can recommend how to best integrate these components into new or existing curtain wall systems to expedite the production process for the fabricator and the installation process for glazing contractors.

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The industry as a whole is now realizing advanced FRP is available as an option for curtain wall design, too. Therefore, many curtain wall systems used today are similar to those designed back in the 1980s and 1990s. Often, it is through industry conferences, such as The Buiding Envelope Conference and GlassBuild America, that designers are seeing these materials firsthand.

An example of FRP technology in use was in the upgrade of an old, drafty curtain wall at a Porsche/Maserati dealership. The owners needed a new curtain wall that would parallel the performance of the brands’ industry leading supercars, considering the previous wall was letting in air leaks and would fog up when it was cold outside. FRP pressure plates were incorporated into thermally broken curtain wall hardware components designed to meet or exceed the industry’s most stringent energy codes. The FRP pressure plates allowed the project to achieve a condensation resistance factor of 80 in the frame and 70 in the glass. In addition to thermal performance, the FRP pressure plates provide structural strength for the entire curtain wall system, outperforming polyamide alternatives in both compressive and flexural strength and exhibiting no creep under sustained loads. The final result delivered a comfortable interior climate for staff and customers. The new curtain wall with FRP technology also reduces the facility’s energy usage for a cleaner, greener footprint.

FRP thermal pressure plates were also used for Vaisala’s North American Headquarters. The custom designed pressure plates were again added to a thermally broken curtain wall system and proved to be a keystone in the development of one of Colorado’s most sustainable buildings. The headquarters was built in Scandinavian style with an exceptional energy-efficient profile. FRP thermal pressure plates were combined with warm edge spacers to achieve a system U-factor of 0.32 with excellent condensation resistance (up to 80 CRF), as well as exceptional air, water, structural, and acoustic performance all confirmed by independent laboratory testing.

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Conclusion

Curtain wall usage is accelerating in commercial construction; therefore, it is critical for all construction stakeholders in charge of the design, fabrication, and specification of curtain walls and their components to seek the industry’s highest-performing solutions.

Identifying manufacturers that can create an array of applicable curtain wall components that address thermal bridging, condensation, structural integrity, and long-term durability will be critical for the many developments seeking LEED certification or those striving to achieve near- and long-term greenhouse gas (GHG) emission targets.

Notes

¹ Refer to the curtain wall section at fgiaonline.org/pages/curtain-walls[5].

² Visit the National Fenestration Rating Council (NFRC) 101-2020.

[6]Author

Greg Koch is the vice-president of sales and marketing for Deceuninck North America and has been with the organization for nearly nine years. Koch is a hands-on executive leader with deep expertise in the fenestration and window and door extrusion industry. Over the past 30 years, he has held leadership positions at several top organizations dedicated to window, door, and curtain wall manufacturing.

Source URL: https://www.constructioncanada.net/advances-in-curtain-walls-fibre-reinforced-polymer-technology/

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