Fiberglass Benefits Drive Contradictory Trend in a Depressed Market
August 30, 2010Fiberglass as a material system in windows and doors continues to gain momentum. The AAMA/WDMA 2009/2010 U.S. Industry Market Studies show, for example, that while the demand for window units of all types plunged a heart-stopping 44.8 percent during the recent contraction from a 2005 peak to the trough in 2009, the market share for fiberglass nearly doubled from 1.6 percent to 3.1 percent. That share is expected to reach 4.3 percent in 2013, led primarily by sales for new construction applications. While these share figures are still small, the trend is clear, and several mainstream window and door manufacturers have introduced fiberglass lines to their array of window and door products over recent years.
The fiberglass success story is traceable to the following benefits:
- High tensile strength
- High strength-to-weight ratio (light weight)
- Stiffness
- Compatible thermal expansion
- Low thermal transmittance (U-factor)
- Acoustic properties and good insulation
- Durability (low-maintenance life cycle)
- Flexible and attractive finishing options
- Sustainability
High Strength
Fiberglass profiles have about the same strength as steel (based on tensile strength) and are thus able to be fabricated in large sizes with large expanses of glass, without the need for extra support or reinforcement. They exhibit strong wind load performance and good forced entry resistance, even in relatively narrow profiles. This makes fiberglass windows applicable to many commercial as well as residential applications.
High Strength-to-Weight Ratio
The relatively light weight of fiberglass gives it a high strength per unit of weight – another benefit for designing larger window products, as well as those with complex integral shapes and minimal sightlines. This enables accurate historical replication for restoration projects, as well as maximizing daylighting to enhance green building designs.
Stiffness
The high modulus of elasticity means fiberglass windows have the ability to resist deformation or bending under load, reducing sash sagging or mullion deflection. This ensures smooth operation over a long service life, reducing the stress on operating hardware. Large expanses may need reinforcement, however, to meet the industry standard L/175 deflection limit for high-performance structures.
Strength and stiffness facilitate the installation process, in that windows remain square, level and plumb. They also resist warping throughout handling, installation and in use for long-term leak resistance.
Compatible Thermal Expansion
Fiberglass frames and glass windowpanes have a similar coefficient of thermal expansion (CTE), which means the window will readily maintain frame-to-seal integrity through daily and seasonal temperature swings. This reduces the potential for air infiltration, a major factor in a building’s loss of energy efficiency.
Low Thermal Transmittance
Fiberglass’ competitive U-factor (the cornerstone of energy efficiency), aids in energy efficiency and thus provides for lower building operating costs, higher condensation resistance and increased occupant comfort. This is particularly important in these days of conservation consciousness and green building practices.
In 2009, DOE significantly tightened ENERGY STAR® Window performance criteria. Northern climate zone U-values ranged from under 0.30 up to 0.32, based on tradeoffs of solar heat gain. North Central and South Central Zones required 0.32 and 0.35 or less, respectively, while the Southern Zone limited U-factor to 0.60.
However, this higher performance bar remains well within the capabilities of fiberglass-framed windows, which exhibit typical U-factors of 0.22-0.29, depending on the glazing. Plus, any fiberglass-framed windows, like products framed with other materials, can attain required solar heat gain coefficient (SHGC) values by using spectrally-selective low-E glazing (typically within the 0.21 – 0.41 range).
Further updates of ENERGY STAR are on the horizon for development starting in 2011 and introduction in 2013 or 2014, as EPA takes over the ENERGY STAR reins from DOE. While most of these upgrades appear likely to involve field testing, durability and installation, changes to air infiltration requirements and life cycle analysis being considered appear to also be conducive to fiberglass’ positive attributes.
Acoustic Properties
Excellent heat transmission performance also has the added benefit of offering good insulation against sound transmission – a plus for homes or institutions in noisy urban environments.
Durability
Fiberglass windows offer high performance over a long service life. They can handle both extreme cold and heat, and resist rot, corrosion and peeling. This makes them excellent candidates for use in corrosive seacoast environments. In addition, fiberglass is extremely hard and thus highly scratch, dent and impact resistant, and its strength is unaffected by time or temperature. This durability makes installed fiberglass fenestration essentially maintenance free, although it can be easily painted when desired for a rejuvenated décor.
Flexible and Attractive Finishing Options
The attributes of dimensional stability – low thermal expansion and contraction – allow fiberglass to be coated in a full range of colors – bright white to pitch black, and everything in between – and still stand up to the extreme temperature and UV exposure ranges from Arizona to Alaska.
There are a variety of both liquid and powder coatings for fiberglass in use today, and all have their own application technologies. Common among these are environmentally-friendly water- and solvent-based liquid coatings (acrylic enamels, polyurethanes, etc.) and dry coatings, such as powder coatings, similar to those used with aluminum. Also available are acrylic capstocks, which are typically co-extruded with the pultrusion of profiles.
As with exterior coatings, a variety of options are also available for interior finishes. Wood veneer interiors are popular, giving a composite fiberglass window or door the appeal and warmth of wood. The veneer is composed of very thin slices of wood (as thin as .020”) and comes in a variety of species, vertical grain fir, oak, alder, pine, etc.
Sustainability
Fiberglass is also a sustainable material with widely available raw material feedstocks and an excellent life-cycle cost profile. In fact, EPA has said that pultruded fiberglass is “truly” environmentally friendly based on product longevity and embodied energy, as well as limited use of resources and low pollution levels emitted during the manufacturing process.
Its inherent inertness also makes fiberglass non-magnetic, non-reflective and non-sparking and can be formulated for low flammability.
A 21st Century Material
The only attributes that have opposed a potentially faster penetration of the market by fiberglass fenestration are two-fold: its price and lead-time, attributed primarily to the complex fabrication process.
Yet as consumers weigh the short term vs. long-term costs, fiberglass is becoming the choice for some homeowners because of what fiberglass has to offer them.
And, onrushing advances in raw materials, the pultrusion process, die design, coating technology and fabrication and assembly equipment continues to accelerate as the demand increases. Such advances have already driven down the cost and improved lead time capabilities. This trend, along with recognition of the performance benefits, is propelling fiberglass windows and doors ever further into the mainstream – undeterred by the construction recession and spurred by green initiatives.
American Architectural