Fiberglass Windows: A Sustainable Choice in Non-Residential and Multi-Family Buildings

Selecting a window system for use in new or renovated commercial and institutional buildings has typically centered on aluminum, steel, aluminum-clad wood, or vinyl windows. In the last five years, however, another choice has gained popularity for a lot of good reasons. Fiberglass window systems are being specified and installed more and more in retail facilities, offices, schools, colleges, condominiums, apartments and many other buildings that commonly have relied only on metal window systems in the past. To understand this emerging trend, let's begin by looking at some of the basics of fiberglass window technology.

Natural Materials Blended with Technology

While the term "fiberglass" is used as if it were a single material, it actually is a composite that consists of glass fibers and a resin that binds those fibers together. Glass fiber, made from natural silica and other materials, has a surprisingly high tensile strength. This characteristic has been demonstrated in many building product applications showing it to act like the equivalent of many reinforcing bars in a concrete mix. The resin that is introduced acts like the concrete itself that forms and holds everything together with the added benefit of performing well in compression. Combined together, the glass fibers and resin create a material that is stronger than either of them individually and provides strength in both compression and tension.

A key point to remember is the type of resin used to make the composite fiberglass material. In general, all resins can be put in one of two categories: thermoplastic or thermoset. In simple terms, thermoplastic materials can be re-melted while thermosets cannot. Most commonly used plastics are made from thermoplastic resin including vinyl windows which are made from PVC, a thermoplastic resin. These materials soften as they are warmed and if heated high enough will melt. This is how plastics are recycled. Thermoset materials, in contrast, undergo an irreversible chemical reaction. Often initiated by heat, once this chemical reaction has occurred, thermosets do not soften or melt as they are reheated. Fiberglass composite windows are made using thermoset resin. As a result, fiberglass composite windows can be used in hot climates and can be painted dark colors, even in high sun exposure applications. If vinyl windows are used in these applications, it is possible for the vinyl to soften, causing the material to sag or warp. The term, "vinyl smile," is sometimes used in the industry to describe this phenomenon. This is most often seen when the head of a large span sags after becoming too hot.

The process of making fiberglass window frames is also different from making aluminum or vinyl frames where the process of extrusion is used, which means the material is pushed through a die to shape. Instead, fiberglass frames rely on a process called pultrusion, in which thousands of glass fibers (called rovings) are pulled through a steel die. (See Figure 1.)The resin and fiber are given shape as they are pulled through the die which is heated to initiate the resin's cure process. The hardened result is then cut to the desired length and prepared for finishing. A paint finish is applied to the fiberglass to provide the final coloring and UV resistance to protect the finished product from sun exposure.  In testing performed in accordance with the American Society of Testing and Materials (ASTM) testing standards, fiberglass composites manufactured in this manner consistently display superior performance in strength, ability to withstand extreme heat and cold, and resistance to dents and scratches.

There are several characteristics of fiberglass composite windows that have contributed to their increased use in commercial and institutional buildings, including:

• Durability. In addition to its great strength, certain factory-applied finishes render fiberglass composite virtually indestructible and long lasting. Further, it will not corrode or rot.

• Impact resistance. (See Figure 2.) Fiberglass composite withstands major impacts without deformation, especially in cold weather. Impact resistance is particularly important on the job site during installation, when dents and damage may inadvertently occur.

• Hot and cold performance.Fiberglass composite can handle a wide range of temperature extremes, withstanding heat up to 200 degrees Fahrenheit, and cold to -40 degrees Fahrenheit.

• Thermal expansion. (See Figure 3.) Fiberglass composite has a very low coefficient of expansion which is very similar to glass. As a result, it moves very little as the weather changes, resulting in less stress on the installation, seals, and glazing of the window. In addition, since fiberglass composite is very heat tolerant, it can be painted dark colors without concern for heat deformation.

• Energy efficiency. (See Figure 4a & b.) Fiberglass composites rank high because of their inherently low heat conductivity. Further, they are commonly offered with added insulation inside the cavities of the frames and sash, boosting the overall thermal resistance value of the unit. As a result, the material also has a higher condensation resistance than other materials. As shown in Figure 4a, fiberglass window units rate 2.4 times better than aluminum with a thermal break and even better compared to aluminum frames without a thermal break. As a result, they also provide superior thermal comfort to those seated near windows.
• Sustainability. Fiberglass composites consume less embodied energy to produce when compared to aluminum and vinyl.

• High performance. The finished units provide excellent resistance to air and water infiltration particularly in high winds making them very appropriate for coastal applications. They also serve as effective sound barriers between outdoor and indoor spaces.

• Finish. The final factory applied finish coat is typically scratch resistant, low-maintenance, and resists chalking and fading-even in dark colors.

• Installation, operation and maintenance. Fiberglass composite units typically arrive on-site pre-assembled and pre-finished, which makes them easy to install, and low maintenance over the long term.

The net result of all of these characteristics is that fiberglass composite windows offer an advanced alternative for commercial buildings of all types. They provide exceptional energy efficiency and durability even in extreme weather conditions while combining the beauty of durable finishes with the outstanding performance commercial projects demand.

Read More

Cool Roofs for Hot Projects

Imagine specifying a roof that is visually dynamic, yet also reduces cooling energy loads by 30 percent, combats global warming, and decreases roof maintenance costs. This miracle roof can meet all your expectations for comfort, cost and aesthetics and it is not some product from the future-it is a cool roof.
Technological advancements and ecological awareness have evolved cool roof materials from the flat, white roofs of yesterday to the myriad colors, materials, and profiles of today. Because they are so versatile, cool roofs can be applied to all styles of projects, from pitched residential to flat commercial roofs. Innovative technologies are pushing the "building" envelope with cool roofs that self-clean, change color accordingly to the temperature, or are holographic, bringing countless design options to an architect's table.

The extent of the energy benefits to be gained from cool roofing correlates to the building's location, type and use, as well as to the specific radiative properties of the selected roofing product. Fortunately, there is a broad range of locations in which cool roofs are proving to be a viable energy efficiency measure. Simply put, cool roofs are roofing products that integrate materials with greater spectral reflectance than their traditional, non-cool counterparts, and thereby minimize the transfer of heat to the building below. This is true for a broad range of product types, colors, textures and roof slope applications.

Cool Roofs 101:

Deciphering the Language of Cool Roofing

The energy performance properties of a roof can be determined by two characteristics of the surface layer: solar reflectance and thermal emittance (see diagram above). These radiative properties describe the roof's ability to minimize the solar heat gain of a building by first reflecting incoming radiation and then by quickly re-emitting the remaining absorbed portion. As a result, the cool roof stays cooler than a traditional roof of similar construction.

When sunlight hits an opaque surface, some of the energy is reflected. The measured fraction of solar energy that is reflected by a roofing material's surface is called solar reflectance, or albedo. Solar reflectance is measured on a scale of 0 to 1, where the higher the solar reflectance value the "cooler" the roof. High albedo, more reflective surfaces stay much cooler than low albedo, less reflective surfaces. Energy that is not reflected by the roof is potentially absorbed by it; this is where thermal emittance comes into play.

Thermal emittance is the relative ability for the roofing material to re-radiate absorbed heat as invisible infrared light (relative to a black body radiator). This absorbed heat will either be gradually or quickly re-radiated away from the roof; the quicker the better because the longer the heat is trapped at the surface of the roof the more likely it is to be transferred to the building below. Thermal emittance is also measured on a scale of 0 to 1, where a roofing material with a higher thermal emittance will re-emit absorbed thermal energy more quickly than a material with a low emittance and will result in a "cooler" roof.

Though most roofing materials have a fairly high thermal emittance, in order to accurately determine a roofing product's "coolness," or its ability to shield the building beneath it from heat, both solar reflectance and thermal emittance must be measured. It is possible for a roofing product to have mixed emittance and reflectance values ranging from very high to very low, although products with either a low reflectance or emittance would not typically be considered "cool" roofs. It is important to note that a high emittance value alone will not result in a "cool" roof nor will a high reflectance value alone. The Solar Reflectance Index can be a useful tool for determining the overall thermal properties of a roofing product

.

Solar Reflectance Index (SRI)

Codes, standards and programs that specify cool roofing requirements may also reference an additional calculated value, the Solar Reflectance Index (SRI). SRI allows actual measured solar reflectance and thermal emittance values to be combined into a single value by determining how hot a surface would get relative to standard black and standard white surfaces. In this manner, SRI measures a material's ability to reject solar energy, based on a scale of 0 to 100.

The standard black roofing material has a high emittance value (90 percent) but a low reflectance value (5 percent). This creates a hot roof surface because even though the emittance is high, there isn't enough reflectance to prevent excessive heat gain. As such, the standard black roof is given an SRI value of 0.

The standard white roofing material is highly reflective (80 percent) and has the same emittance as the standard black surface (90 percent). Its surface is much cooler and the standard white roof is assigned an SRI value of 100. It is important to note that materials with particularly poor or good radiative properties can have a negative SRI value, or a value that exceeds 100. Like solar reflectance and thermal emittance, a higher SRI value is synonymous with a cooler roof.

Calculating SRI

Lawrence Berkeley National Laboratory (LBNL) hosts an easy-to-use SRI calculator on their website. All that is required is the solar reflectance and thermal emittance values and the tool will calculate the SRI. The calculator is located at coolcolors.lbl.gov.

Cool Roofing:

A Win-Win for Building Owners and the Environment

When properly installed and maintained, cool roofs provide numerous benefits that contribute to the health of a community, to the occupants of the building and to the owner's pocket book.

Among the benefits to the building occupants and owner are:

• Improved comfort for occupants. The building's interior is subject to less thermal flux and stays cooler during the warm season.
• Energy savings from reduced cooling energy loads.
• Longer air conditioning unit life resulting from decreased use.
• Increased roof durability due to reduced thermal flux, as cool roofs can stay up to 70 °F cooler than dark roofs.
• ^{Cool roofs are distinguished among energy conservation measures because of the many environmental benefits they can provide. A crucial benefit of cool roofs is their ability to help mitigate the urban heat island effect. The urban heat island effect is a phenomenon that is characterized by a measured increase in the ambient air temperature in cities over their surrounding rural areas. This is due to roofs and other non-reflective surfaces that absorb and trap solar radiation-or heat. Cities can be 2° to 8°F warmer than their surrounding areas because this trapped heat gradually warms the ambient air temperature throughout the day and nighttime hours warming the urban core without any opportunity for temperatures to drop at night.2 Cool roofs help improve urban conditions by:}

• Contributing to cooler ambient temperatures by immediately reflecting solar radiation back into the atmosphere before it can degrade to heat, as well as reemitting a portion of infrared light.
• Indirectly reducing air-conditioning use by lowering the ambient air temperatures.
• Improving grid stability and increasing peak energy savings by reducing the need for air-conditioning at the hottest times of the year.
• Improving the Air We Breathe

Through mitigation of the urban heat island effect with the reduction of ambient air temperatures, cool roofs also improve air quality. Smog is created by photochemical reactions of air pollutants, and these reactions increase at higher temperatures. In Los Angeles alone, mitigation measures that reduce the average air temperature by 5 °F could yield a 12 percent reduction in smog (ozone) worth $360 million/year.³ Lower ambient air temperatures and the subsequent improved air quality also result in a reduction in heat-related and smog-related health issues, including heat stroke and asthma. In addition to the reduction of greenhouse gas emissions such as CO2, by conserving electricity for air conditioning cool roofs reduce the emission of nitrogen dioxide and sulfur dioxide particulates from power plants.

Specifying the Perfect Roof: Product Rating Resources, Product Types, Building Programs and Codes

A cool roof should be chosen based on the slope of the roof, energy savings goals, the project location and climate, local code requirement or green building credits, as well as aesthetic preferences. Designers who are seeking sustainable design credits may also want to consider the cradle-to-cradle aspects of their materials choices, including recycled content, end of life recyclability and avoidance of toxic materials. Other sustainability considerations include the source location and weight of the product, which affect raw material use and shipping fuel, as well as the environmental impact of raw material extraction and manufacture processes.

Once the project parameters have been established, an appropriate roofing product must be selected. Several building codes, as well as voluntary green building programs, either require or allow you to achieve credits for including cool roofs in a project. Fortunately there are product rating resources available to help you specify the perfect cool roof for your project.

Product Rating Resources

Rated product databases can assist the designer in selecting an appropriate cool roof product because they list pertinent product information that can be easily compared. The designer can search roofing products by the initial and aged solar reflectance, thermal emittance, and SRI values as well as the slope application and type of roofing material. Most specifications define a low-slope roof as having a pitch less than or equal to 2:12 and a steep-sloped roof with a pitch greater than 2:12.

While existing rating systems are complementary to one another, they do have slight differences in their requirements. ENERGY STAR, for example, aims to capture the most efficient products and set minimum requirements for both initial and aged solar reflectance. In order for a product to be listed by ENERGY STAR, it must meet their minimum requirements (initial solar reflectance of 0.65 and three-year aged value of 0.50 for low-slope products and an initial reflectance of 0.25 and aged value of 0.15 for steep sloped products). The Cool Roof Rating Council (CRRC), on the other hand, does not set minimum requirements, but does require that all testing be conducted by a licensed CRRC-accredited Independent Testing Laboratory. The primary values of independent ratings for the CRRC are standardized and consistent test methods for initial and aged ratings, credible test results, a strict chain of custody, equal subjection of products to weatherization in key climates, and reliable product comparisons.

Both rating systems include aged testing, where products are exposed to natural weather conditions for a three-year period of time. The CRRC uses three specific locations representing three key climate zones (hot/dry, hot/humid, and cold/temperate) to determine aged product performance. ENERGY STAR allows aged testing to be conducted on existing roofs in place of weatherization, but also accepts products that have been rated by the CRRC so long as the ratings meet ENERGY STAR's minimum requirements for both initial and aged reflectance values. The most reliable source for solar reflectance and thermal emittance data for cool roofs is independent roofing product ratings.

Product Types

The following is a list of common roofing materials. Once you have determined the appropriate material for your project, you can find cool roof options for most of these product types. Two useful resources to search for cool roofs by product type are the CRRC's Rated Product Directory and the ENERGY STAR Roof Product List.

• Field-Applied Roof Coatings. Field-applied coatings are applied directly onto the roof surface, either on a new roof assembly or over an existing roof surface and may require an appropriate primer. Once applied, the coating is what determines the reflective properties of the roofing product.
• Foam Roof Systems. Field-applied foam systems are sprayed on in liquid form and harden as they set on top of the roof. Factory-applied foam systems are formed into rigid panels and coated with a reflective coating in the factory. The foam usually gives the roof system additional insulation properties and the coatings provide the "cool" rating.
• Metal. Metal roofing products can be shaped to look like shingles or shakes, or to fit unique curvatures, in addition to a typical standing seam configuration. They come in a variety of factory-applied textures and colors, including darker "cool" colors with infrared reflective pigments. Metal products can also be coated in "cool" custom colors to meet a variety of client preferences.
• Modified Bitumen and Built-Up Roofing. Modified bitumen is bitumen (asphalt or tar) modified with plastic and layered with reinforcing materials then topped with a surfacing material. Built-up roofing (BUR) consists of built-up layers of coated asphalt and insulation applied on site and can be covered with a capsheet or field-applied coating (surfacing materials). The "cool" part of these roof products refers to the reflective properties of the capsheet, top coating or surface granules.
• Shingles. These roofing products are commonly used for residential or steeper-sloped buildings, including some commercial buildings. For "cool" colored shingles, the heightene d solar reflectance comes from granules that contain solar-reflective pigments.
• Single-ply. Single-ply roofing is a pre-fabricated sheet of rubber polymers. Single-ply roofing is laid down in a single layer over a roof. The single-ply membrane can be firmly set on the roof and attached with mechanical fasteners or adhesives. There are two main types of single-ply materials: single-ply thermoset and single-ply thermoplastic. These roofing products can be specified with an ultra-violet-resistant and highly reflective surface.
• Synthetic Polymer Composite Products. These polymer injection molded roofing products can be shaped into any form, often to look like wood shakes, tile or slate roofing products. "Cool" composite products are selected by color, or may have cool reflective pigment colorants built into the polymer formula. Some composite products are additionally sustainable are more sustainable if they are made from recycled materials or can be recycled after full-life use.
• Tile or Pavers. Tile products (clay or concrete) are available with solar-reflective surfaces that increase the number of "cool" colors from which the designer can choose. Additionally, the dense, earthen composition of tile products provides increased thermal mass and ventilation properties, which yield additional energy savings that are not captured through solar reflectance and thermal emittance measurements.

Solar and Green Roofs

Cool roofs can be designed to complement other sustainable roof systems allowing designers to maximize their roof options by combining green roofs and solar collection systems with cool roofs. Each sustainable system offers unique benefits and although green roofs and solar collection systems are not considered cool roofs, their benefits can be enhanced with a cool roof.

Green roofs or "living roofs" use plants as the roof covering. While green roofs have many benefits such as providing habitat, increasing roof lifespan, and reducing storm water runoff, they do not have high reflectance, a key feature of cool roofs. If you are specifying a green roof, consider using cool pavers for the pathways and using a cool roof on the non-green roof regions. Cool pavers act similarly to cool tile roofs, helping maintain a cool surface and ambient air temperatures that create a more pleasant environment for occupants and plants.

Several studies are currently being conducted on the interplay between cool roof coatings and solar photovoltaic systems. Because cool roofs can keep the roof surface 70 °F cooler than dark roofs, cool roofs may maintain solar photovoltaic and solar thermal systems at optimal temperatures, improving both performance and lifespan of the systems.1 Some solar photovoltaic systems are even designed with curved surfaces to capture solar radiation reflected off the cool roof surface

Comprehensive Design with a Cool Roof

Smart designers consider the pros and cons of a variety of sustainable design features for one project. A combination of energy efficient and energy generating design features can be used in passive solar design. You may choose to specify a cool roof coating and solar photovoltaic panels on the south side of the building to capitalize on the higher solar exposure. Tall plants on a green roof may be used to shade windows oriented west from high solar gain, or to distract from an unpleasant view. If your project has a tight budget, the vast array of cool roof options allows you to specify a cool roof for areas of the building that receive high solar radiation, such as the south and west sides of a pitched roof, while saving money on a visually similar, yet not cool product for the northern side. When designing your next project, consider integrating multiple roofing products or technologies to take advantage of their distinctive benefits.

Aging and Maintenance

Solar reflectance and thermal emittance are surface properties. The "coolness" of a roof is therefore dependent on the surface condition of roofing products, which must withstand years of harsh climates, solar radiation, pollutants and algae growth. ORNL studied the three-year aging and weathering of cool roofing membranes made of single-ply roofing at various locations across the United States.⁶ Results indicated that when washed with detergent, the majority of the roofs will still provide 90 percent of their un-weathered reflectance (in some cases an algaecide was required). Standard maintenance practices as suggested by the roofing manufacturer will keep your cool roof "cool" for a longer period.

Read More