Aluminum vs. Fiberglass vs. RAU-FIPRO

Aluminum

Aluminum window profiles offer numerous advantages:

• a highly versatile structural material
• very rigid, with a modulus of elasticity (E) of approximately 60 GPa, although not as rigid as steel (E~200 GPa)
• strong and durable
• approximately one third the density of steel, allowing properly engineered aluminum systems to achieve excellent strength with significantly less weight
• most alloys are corrosion resistant

These characteristics make aluminum an excellent material for windows and doors, particularly in warm and moderate climates. However, aluminum’s greatest strength is also its greatest weakness: it conducts heat extremely well. As a result, aluminum windows and doors can present several challenges in colder climates:

• suffer in cold climates
• poor energy efficiency
• greater susceptibility to condensation

Despite these limitations, aluminum remains widely used where structural performance is the primary consideration. Most people have experienced sitting beside an aluminum-framed window on a cold day in a restaurant or commercial building and feeling the cold radiating from the frame. Until recently, there have been few materials capable of delivering comparable structural performance while significantly improving thermal efficiency.

Fiberglass

The 20th century brought a revolution in composite materials, many of which combined reinforcing fibers with a plastic matrix. The most familiar example is fiberglass, which consists of glass fibers embedded in a polymer resin. Composite materials became increasingly popular in aerospace and other high-performance applications, often complementing or replacing aluminum because of their unique combination of strength and thermal performance. The most common matrix is a thermoset plastic. A thermoset plastic, once cured, cannot be melted for reshaping or joining.

Fiberglass window profiles have been used successfully for decades and offer several key advantages:

• excellent structural properties
• low thermal conductivity

Conventional fiberglass profiles have become a popular alternative to aluminum in very cold climates though time has shown a few drawbacks to these systems: 

• First, because traditional fiberglass profiles use glass fibers embedded in a thermoset resin, corners must be joined mechanically or bonded with adhesives rather than welded. Over time, these joints can deteriorate, potentially allowing water infiltration into the building envelope
• Another challenge is screw retention. Conventional fiberglass does not hold screws particularly well because the fasteners can cut through the glass fibers, reducing long-term holding strength. While aerospace applications overcome these issues through highly engineered fastening methods, those solutions are generally impractical for window hardware, operators, and hinges.

RAU-FIPRO

In the mid-2000s, REHAU transformed the window industry with the introduction of RAU-FIPRO, an advanced glass fiber composite material that combines the strength of fiberglass with the versatility of a thermoplastic matrix. Unlike conventional fiberglass systems that rely on thermoset resins, RAU-FIPRO can be extruded into complex profile geometries. This allows for:

Access Windows & Doors built with RAU-FIPRO deliver the benefits of fiberglass without many of the drawbacks associated with conventional fiberglass systems. By combining RAU-FIPRO glass fiber composite profiles with engineered reinforcement couplings, we can span window and door openings that were once achievable only with aluminum systems. Our mullions are specifically engineered so that structural reinforcements, rather than the glass itself, carry the design wind loads. This approach helps prevent premature glass stress and failure while maintaining exceptional structural integrity.