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.

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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.

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Green at Its Core

An innovative and robust seismic frame is a key part of a San Francisco office building's sustainable strategy and its bid for LEED Platinum.

CANADA PHARMACY

Postponed and nearly derailed several times, the just-topped out concrete structure of the 13-story office building at 525 Golden Gate Avenue, a half block away from San Francisco City Hall, now seems on a smooth path toward completion next summer, more than a decade after the project was first conceived. Twelve years ago, the city acquired the site, which contained a vacant state office building damaged beyond repair by the 1989 Loma Prieta earthquake. The intention was to build a new tower, designed by a joint venture of the San Francisco−based firms Kaplan McLaughlin Diaz (KMD) and Stevens + Associates, for several city departments. But in 2002, with design development for the 277,500-square-foot building well advanced, work stalled in the wake of the dot-com bust.

Then in 2006, the San Francisco Public Utilities Commission (PUC) resuscitated the project with plans to consolidate 1,000 employees from two leased locations. The city already had green goals for the building, targeting a LEED Silver rating. But the PUC, which provides water, wastewater treatment, and power generation services to city and Bay Area customers, had more aggressive goals, asking for a revised design that would achieve LEED Platinum and include on-site renewable power and a wastewater-reclamation system, among other features. But before construction could begin, the project was almost scuttled again when estimates solicited in 2008's heated construction market came in several million dollars over budget.

After a rigorous value-engineering exercise, the now $133 million building is still on target for the higher rating. The tower will use one-third less energy from the grid than a typical office building, saving $118 million in energy costs over the next 75 years, according to Brook Mebrahtu, 525 Golden Gate project manager for the city's Department of Public Works.

To achieve these savings, the building deploys a host of tightly coordinated resource conservation and energy production measures that are almost de rigueur on a green office tower. Except for a swath of Sierra white granite that appears to travel over the roof between the east and west facades, the tower is wrapped in double-glazed, high-performance curtain wall. The building has interior and exterior shading devices for controlling glare and minimizing heat gain, light shelves for daylight harvesting, an under-floor air-distribution system, and a 200 kW roof-mounted photovoltaic (PV) array expected to supply about 7 percent of the facility's electricity.

The building also incorporates a few technologies that are still considered a bit exotic. For example, the tower will have a "living machine."

It includes a man-made wetland that will serve as an ornamental feature at the perimeter of the lobby. By mimicking natural processes and relying on plants and other beneficial organisms, the system will cleanse the gray and blackwater generated by the tower, making it suitable for uses such as toilet and urinal flushing. The PUC also hopes to use the reclaimed water for irrigation, but San Francisco does not yet have a permitting process for such systems. According to Mebrahtu, the state and city departments of public health are currently reviewing the relevant regulations.

Another unusual element of 525 Golden Gate is building-integrated wind technology. Six to eight vertical axis turbines, of about 1 kW each, will be mounted on a stair tower on the north facade, taking advantage of a steady wind from the north-northwest. Although they are expected to generate less than 1 percent of the electricity consumed by the building, the PUC will have the option of swapping the turbines out for more efficient ones when the still-nascent building-integrated wind technology improves. In addition, the rotating turbines will serve an important function as a visible source of renewable power, points out Todd Ravenscroft, an associate and project manager in the San Francisco office of Arup, which developed the building's mechanical engineering concept. "You won't be able to see the PVs making energy," he says

The turbines and the wastewater-reclamation system are on the leading edge. However, they are not the building's most unusual sustainable elements. Arguably, it is the structural frame, described as "self-healing" by the project's Berkeley-based seismic consultants, Tipping Mar. After a design basis earthquake (DBE) - a major temblor calculated to have a return period of about 475 years - the tower should remain  undamaged and safe for employees to occupy immediately. And after a much more powerful and statistically less likely event - a maximumcredible earthquake (MCE) - one with a 2,475-year return period - the building should suffer negligible damage. A MCE is the most severe earthquake that can be expected to occur at a given site on the basis of geologic and seismologic evidence. But following such an event, the PUC building should need repair only to the skin or other architectural elements. 

The LEED rating system contains no credits that pertain to seismic design. Nevertheless, the PUC team members regard the structural frame as one of the building's primary green attributes. They hope that this durability will earn the project points for innovation. "Resilience is one of the fundamental design goals," says David Mar, Tipping Mar principal. "It is deeply coupled with the client's notion of sustainability."

The structural system includes what is sometimes referred to as a "rocking mechanism" because its

elements are designed to return to their original position after an earthquake's shaking. It relies on post-tensioned concrete slabs and two vertically post-tensioned concrete cores. The tensioned tendons, housed unbonded inside ducts placed between the rebar, provide a restoring force, closing cracks that will develop in the concrete during a quake, explains Mar.

Initially, plans for the PUC building called for a steel structure - one with the same column grid and core locations - but with a special-moment frame that included viscous dampers. Like the post-tensioned concrete building under construction now, the steel version was designed to allow the agency's staff to maintain continuous operations after a DBE. But during a more extreme event, the concrete frame should perform better, especially in the area of internal acceleration, says Mar. For example, his team studied the ability of the two sytems to protect mechanical equipment secured with standard bracing. They found that the concrete scheme was able to withstand higher accelerations.

Curiously, this level of performance was not the primary motivation for the substitution in structural systems. Instead, the main impetus was the need to cut costs. The moved shaved about $10 million from the construction price, with about half of those savings attributed to the associated elimination of architectural elements, such as fireproofing and finishes, including suspended ceilings. This approach meant that much of the poured-in-place structure would be left exposed, a look that the PUC apparently had no objections to. "You need a client who is able to accept that aesthetic," points out David Hobstetter, KMD principal.

One bonus of the redesigned structural system was that it permitted the team to reduce the floor-to-floor height by a foot and insert an additional office level within the same zoning envelope. But it also provides other synergistic advantages - for the daylighting scheme in particular. The new concrete structure eliminates the sunlight-blocking deep perimeter beams that were a key part of the special moment frame solution. In addition, the new frame allowed designers to taper the underside of floor slabs toward the curtain wall to help bounce the sun's rays from light shelves to the ceiling, and then into the interior of the largely open office floors.

Photo cells control indirect lighting, dimming fixtures when daylight levels are sufficient. To make sure the ceiling's color would be compatible with this illumination strategy, designers set a minimum reflectivity for the concrete in the project's specifications - an unusual request for poured-in-place construction. "We received a lot of RFIs," says Hobstetter.

The PUC has a raised floor for managing data infrastructure and for distributing conditioned air. The system was also included in the steel-framed version of the building, but the cavity provides an added benefit now that the structure is made of concrete. The structure's mass should act like a thermal battery, storing heat generated by people, equipment, and lighting during the day. At night, facility managers should be able to purge this heat by drawing cool outdoor air through the under-floor cavity, helping reduce load on the building's chillers. Unfortunately, because of the limitations of analysis software, engineers weren't able to fully exploit the heat-storing capacity of the structure in their design so that they could, for example, make mechanical equipment smaller. "Modeling tools don't quantify the contribution of thermal mass well," says Ravenscroft.  "But we believe there is some benefit."

While the project team tried to make the most of any synergies between the frame and the other building systems, at the same time they worked to reduce the embodied energy typically associated with a concrete structure. To minimize its carbon footprint, engineers have substituted about 70 percent of the Portland cement in a standard concrete mix with supplemental cementitious materials (SCMs), including slag (a byproduct of steelmaking) and fly ash (a byproduct of energy generation from coal-fired power plants). By replacing a material that is energy-intensive to manufacture with waste products that might otherwise have be sent to landfills, team members say that they have cut the carbon emissions of the PUC's concrete in half.

The unusual mix has not been without its challenges, especially for the general contractor, Webcor Builders. Although it already had experience with cement replacement, the PUC structure called for a much higher proportions of SCMs than any of the company's earlier projects. With such a high level of substitution, "the products begin to significantly change the dynamics of hydration," says Matt Rossie, Webcor's project director, referring to the chemical reaction that allows concrete to set and harden when cement is combined with water. In general, SCMs like slag and fly ash slow the process, but understanding just how much is critical to estimating how quickly a particular mixture will gain strength, which in turn is important to both the quality of the finished product and the construction schedule.

To help determine how soon formwork can be stripped and when post-tensioning can be applied Webcor and its subcontractor, San Jose−based Central Concrete Supply, are relying on a process known as "maturity testing." The method involves monitoring the heat generated as a result of hydration with embedded sensors and then correlating those results to laboratory tests for the same mix. "Early strength gain is just a function of temperature and time," explains Mike Donovan, Central's manager of technical services.

Relying on this testing method, contractors have been removing forms from the columns about 24 hours after concrete placement and tensioning the horizontal tendons around three days after each slab pour. At press time in mid-May, the frame was almost complete, with only the tensioning of the core tendons remaining. With all the projects' fits and starts, the contractor is relieved to have reached this milestone. Says Rossie, "It's extremely satisfying to see the structural system come to fruition."

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Zeroing In on Net-Zero Energy

With an office building for its Colorado campus, a national research lab aims to prove that super-green can be cost effective and replicable.

Given its mission of developing renewable energy and energy-efficient technologies, it isn't so surprising that the National Renewable Energy Laboratory (NREL), in Golden, Colorado, would want an ultra-high-performance building for the more than 800 staff members it planned to move from leased office space to its research campus at the base of South Table Mountain. The building, the 220,000-square-foot Research Support Facility, or RSF, which opened in June, is designed to be just that. If it performs as intended, the RSF will consume only 35 kBtu per square foot annually, even taking into account the power requirements for a data center that serves all 2,200 NREL employees. This energy use intensity (a measurement of the amount of energy consumed by a building relative to its size) is about 50 percent less than that for one that complies with the 2004 version of the ASHRAE 90.1 standard. If it operates as expected, the facility should also qualify as the largest net-zero energy building in the U.S.

The RSF isn't only about ambitious energy-efficiency goals, however. NREL, which is part of the U.S. Department of Energy (DOE), hoped that the project would demonstrate that large-scale super-green buildings could be both cost effective and commercially viable. With a construction cost of $57.4 million, or $259 a square foot, the RSF's budget is in line with other recently completed office buildings in nearby Denver. "It isn't just a cool building. It is a new class of real estate," says Philip Macey, AIA, director of engineering and sustainability for Haselden Construction, one half of the RSF design-build team.

Net zero defined

What is a net-zero building? At the most fundamental level, it is a building that annually generates enough energy on site from renewable sources to equal or exceed demand. Like the NREL facility, most zero-energy buildings are grid-connected, drawing power from, and supplying it to, a local utility. In the case of the RSF, a 450 kW roof-mounted photovoltaic (PV) array, supplied through a power purchase agreement with solar energy provider SunEdison, serves as the renewable source.

Curiously, a net-zero building was not one of the highest-priority elements of the RSF program. A request for proposals released in late 2007 ranked the client's needs into "mission critical," "highly desirable," and "if possible" project goals. The document, part of a procurement process the DOE has dubbed "performance-based design-build," listed the highest level of LEED certification among the top priorities (the RSF is on track for a Platinum rating), but put net zero with those objectives under the "if possible" heading.

By establishing this hierarchy and deviating from the DOE's traditional design-bid-build delivery method, the owners hoped to encourage teams competing for the project to come up with the optimal design solution within tight schedule and budget constraints. The goal was not to build the least expensive building. "The budget was fixed, so there was no incentive to build the RSF for less," explains Paul Torcellini, NREL group manager for commercial buildings research. "Instead we wanted to achieve the best value with the money we had available," he says.

The design-build team eventually selected for the project - architecture and planning firm RNL and Haselden Construction - aimed to satisfy all of the owner's ambitions, even the items on the wish list. "We decided that if we didn't give the clients everything they wanted, we wouldn't win," says Craig Randock, AIA, RNL principal. Of the three short-listed teams invited to submit a detailed conceptual design, the RNL-Haselden group was the only one that offered a net-zero building in its proposal.

Synergies and strategies

Bringing the aggressive performance goals within reach would require a scheme that lowered energy use with little or no addition to first costs. So even before meeting the rest of the team, Andary began working on the project, performing modeling and simulations. These studies produced an initial concept that included a narrow floor plate to assist daylighting and natural ventilation, a radiant system for heating and cooling, and plenty of building mass to help moderate indoor temperatures.

"We came to the first face-to-face meeting prepared to offer solutions," he says.

The design-build team quickly understood that no one move would make reaching net zero possible. The building would need to rely on a host of tightly coordinated strategies, each offering an incremental benefit, "but when combined, they create synergies," explains Macey, who recently joined Haselden from RNL, where he served as manager of the RSF project.

The scheme ultimately realized has a steel frame and a plan that resembles an out-of-kilter H, with a 454-foot-long, four-story wing to the north and a 364-foot-long, three-story wing to the south, connected to define a pair of courtyards. The wings, devoted primarily to open ­office space, are each 60 feet wide. This depth, along with a system of light shelves and louvers, facilitates penetration of daylight, allowing employees to work with little electric illumination for much of the day.

In addition to reducing the energy consumed by lighting fixtures, this tactic produced a number of additional benefits, including a corresponding reduction in the heat rejected from the lighting, which in turn lessened cooling loads and the portion of the budget that would need to be allocated to mechanical systems and the PV array.

One consequence of the building's configuration, with its elongated, daylight-oriented wings, was more exterior envelope than would have been required by a scheme enclosing the same volume but with deeper floor plates. As a result, the skin was an important focus of the project team's efforts. Designers developed an assembly of insulated precast concrete panels with the required thermal properties. These components had the added benefit of helping speed construction because of their off-site fabrication. Windows, which are triple-glazed, make up only about 25 percent of the long north and south facades. On the much smaller east and west elevations, electrochromic and thermochromic glass, or so-called switchable glazing, helps control heat gain and glare.

The building envelope also incorporates NREL-developed technology - devices called "transpired solar collectors" that consist of perforated corrugated metal mounted on the south facades. These rely on the sun to passively preheat outside air trapped in the cavity between the collectors and the precast panels making up the weatherproof enclosure. The air is then drawn into a crawl space underneath the building. In the winter, the heat from this outside air, along with waste heat from the data center, is stored in the staggered poured-in-place concrete walls making up this "thermal labyrinth." This stored thermal energy is subsequently used to preheat ventilation air delivered to the offices through a raised floor system. In the summer, cool night air flushes the labyrinth and the RSF's occupied spaces. The inertia of the exterior walls, which are left exposed without a drywall interior finish, along with the radiant piping ­embedded in the ceiling slabs, helps maintain the occupants' thermal comfort throughout the course of the day.

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Architecture Animation

Architectural Animation: is a short architectural movie created on a computer. A computer-generated building is created along with landscaping and sometimes moving people and vehicles. Unlike an architectural rendering, which is a single image from a single point of view, an architectural animation is a series of hundreds or even thousands of still images. When these images are assembled and played back they produce a movie effect much like a real movie camera except all images are artificially created by computer. It is possible to add a computer-created environment around the building to enhance reality and to better convey its relationship to the surrounding area; this can all be done before the project is built giving designers and stakeholders a realistic view of the completed project. Architectural renderings are often used along with architectural animation.

WHO USES IT......

Commercial demand for computer-generated rendering is on the rise, but three-dimensional scale models are still popular. Typically members of the AIA (American Institute of Architects) and NAHB (National Association of Home Builders) prefer to use 3D animations and single renderings for their customers before starting on a construction project. These professionals often find their clients are unable to grasp the complexity and spacial qualities of large projects without the help of computer generated visual aids. The animations and renderings are usually supplied by small animation studios.

FUTURE......

Architectural animation is not considered to be the ambition of most small computer rendering firms because of the man hours and computer rendering time that is required to create so many single still images. Not all studios have the software to assemble and incorporate them into a moving sequence. Some smaller companies specialize in high quality single frame computer renderings. Architectural animations require a larger team of artists and animators than single renderings and a much longer time frame is required to complete an animation project. However, many architectural firms are now using architectural animation because it attracts investors and customers who may not know much about building designs. Architectural animation is considered to have a bright future ahead of it as more and more architects and real estate developers are including computer animations in their marketing programs.

• Architectural visualization:

3D rendering

3D walk-through

3D demo of city planning

3D demo of landscape planning

Restoration of ancient architecture

• Animation:

Rendering

Simulation of product and engineering design

• Virtual Reality:

Digital sand-table system for city/community planning

GIS (Geographic information system)

Multifunctional educational system

Simulation and restoration of cultural heritage and ancient architecture

Virtual shopping mall

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The Importance Of Lighting In Interior Design

How you light your house is an important part of redecorating. A change in the lighting can change how the room is viewed. Lighting interior design contributes greatly to the look and feel of a room. There are many types of lighting which can be used in various rooms. We are no longer restricted to a few lamps around the room.

Ambient lighting is a hidden light source that washes the room with a glow. This creates very few shadows and tends to flatten a room. Japanese paper lanterns and wall sconces both produce ambient lighting. For temporary ambient effects, use a dimmer with your ordinary lighting.

Accent lighting provides interest to a room. This method of lighting interior design highlights and object or architectural feature. To use accent lighting, you only need a bulb and a shield to direct the light to the desired focus. Halogen spotlights and opaquely shaded table lamps both provide accent lighting.

Another kind of lighting used in interior design is task lighting. This is a more practical lighting strategy, highlighting an area for daily activities such as reading, cooking, and sewing. Effective task lighting prevents eyes strain and helps with the performance of vital activities. The kitchen is a particularly good place to incorporate task lighting in your interior design. Task lighting sources should be unobtrusive and shielded to prevent glare. Task lighting can be effectively combined with accent lighting to produce lovely effects.

Some lighting can be a work of art in and of itself. Aesthetic lighting is purely decorative, such as a neon sculpture or a spotlight illuminating a statue or painting. This type of lighting must not be used alone, but accompanied by other lighting strategies in your interior design.

Of course, no survey of lighting interior design would be complete without a mention of natural light. Rooms can be arranged to take advantage of the position of the sun at different times of day. This type of lighting is also called kinetic lighting because the light from outside moves. It is one of the less reliable types, as it is affected by the seasons and the weather, but natural lighting can produce an effect unequaled by any artificial light source when used properly.

Lighting is an important tool in your design collection. The way you do your lighting interior design affects the perception of any room. Lighting is also versatile. Using several strategies at once in a room allows you to turn any of them off, changing the look and feel with the flick of a switch. This can be effective for creating different moods in different rooms at night. Light is an essential part of our daily activities. Just like we need air, water and food to survive we need light in order to function efficiently.

Gone are the days when people used to stop working after sunset. The invention of electricity has made life easier and has helped to improve efficiency.

The use of light in interior spaces greatly affects the environment and "mood" inside the space. Here are some of the aspects that can be considered while lighting an interior space.

1) Natural light:

The Sun is the biggest source of light available on our planet.We all are dependant on it. Sunlight is not only required to function but is also responsible for biological balance of the Earth. Sunlight also keeps the air clean by killing any possible bacterial attacks which might be harmful to health.

It is normally assumed that sunlight can penetrate inside a space for about 7 feet (approximately 20 meters). If the architect has taken proper care during planning of the structure, then sunlight can be a very good and free source of ight.

2) Artificial filler lights:

These types of lights work on electricity and are required mostly at the night times. But this is not always true. There are some geographical locations where the weather is cloudy for most months in a year.

At such times filler lights in the form of fluorescent tube lights. These types of light are used to create the same effect that the sunlight would create. As the name suggests. these types of lights "fill" the space evenly with light, eliminating any dark spaces.

3) Special lighting for special spaces:

Special lighting is required at spaces where it is necessary to create a "mood" or special "ambience" inside a space. To achieve this use of color is done. Lighting fixtures like spot lights are used which divert the attention of the crowd at certain focused areas.

These kind of techniques are also used in commercial showrooms, to enhance the importance of the display areas. If you have visited car shows, exhibition pavilions, you will see this kind of lighting extensively used.

Special type of lighting requires more number of light fixtures, because the area they cover is very limited.

4) Extreme lighting:

This type of lighting is used in spaces where the activities have a special purpose, such as movie studios, pubs, dance floors, etc.. Here the lighting used can be of movable types, or can have more sophisticated controls such as intensity, color, movement, controlled through music beats

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