Showing posts with label u-factor. Show all posts
Showing posts with label u-factor. Show all posts

Sunday, November 30, 2008

U-Factor More Important Than R-Factor For Windows and Doors

The window and door industry have their products measured in the form of U-Factor rather than R-Factor. U-Factor is the standard adopted by the National Fenestration Rating Council for windows and doors because it measures the rate of heat transfer (or loss) by the product being rated. It is a more important factor than the R-Factor because R-Factor measures conductivity. Windows and door are obviously not stationary so the measurement of heat loss gives us a better indication of how energy efficient a window or door is.

Radiant heat transfer is heat flow via absorption and then re-radiation.Radiant Heat Transfer

Radiant heat transfer is heat flow via absorption and then re-radiation. (An easy example is when you put your arm into the direct summer sun and it starts to warm up.)

The NFRC gives each window a U-factor rating. The U-factor is the inverse of the more familiar R-factor used in attic insulation. So a U-factor of .5 equals an R-factor of 2. The lower the U-factor the better.

When comparing windows, check for the NFRC label. Look for the U-factor. The first number after the words "U-factor" is the rating that's appropriate for residential purposes. It will be marked "AA" or "Residential." The U-factor marked "BB" or "Non-Residential" is for commercial window applications. Use the U-factor rating to make meaningful comparisons. Be wary of a window vendor who won't provide this number.

How far should you go? Obviously, you need to get price comparisons to make a decision. Keep in mind that a good portion of your cost is installation, so it makes sense to leverage those costs by installing a better window.

Conduction is heat transfer through materials.Convection Heat Transfer

Convection is the transmission of heat caused by movement of molecules from cool regions to warmer regions of lower density. The word "convection" is derived from the latin term convehere (to bring together).

Convection heat transfer is heat flow via air movement. (An easy example is when you turn on a hair dryer and the hot air is projected from the end of the hair dryer.)

Conduction Heat Transfer

Conduction is heat transfer through materials. (An easy example of conduction is when the handle of a pot on the stove gets warm. The heat is being conducted from the bottom of the pot all the way to the handle.)

Convection is heat flow movement.An energy efficient window designed for heating-dominated climates minimizes heat loss by controlling all three sources of heat (energy) transfer.

Creating Energy Efficient Windows For Cold Climates Like Minnesota

The window industry uses the term u-value to measure heat flow. (A lower u-value means better thermal performance.)
There are a number of glass-related options that window manufacturers can use to design energy-efficient windows in cold climates. Most of these techniques improve the thermal performance of the glass. A brief explanation of each follows:

  • Insulating Glass
    Insulating glass is comprised of two (or more) pieces of glass separated by a spacer material and sealed together to create an insulating glass unit (IG unit). IG units reduce convection and conduction heat loss.
  • Low-E Glass
    Low-E glass has an almost invisible, microscopically thin coating that reflects long-wave infrared energy (or heat). When interior heat energy tries to escape to the colder outside, the Low-E coating reflects the heat back to the inside. The Low-E coating reduces radiant heat loss through the glass.
  • "Warm-Edge" Spacer System
    The spacer material separating the two glass panes can be a source of conductive heat loss in cold climates. The thermal performance of IG units can be enhanced by using the SST spacer material that has a lower energy conductance rate and/or has less physical mass which equates to a lower energy transfer path.

Saturday, November 29, 2008

Sustainable Building- PPG's New Century of Architectural Significance

Today’s architects occupy the leading edge of a growing global environmental consciousness. While the industry’s earlier masters were celebrated mainly for the extraordinary design and functionality of their work, the contemporary practitioner is now focused with equal intensity on creating structures that harmonize with the delicate ecosystems they occupy.

Concepts such as sustainability, renewability, reclamation, upcycling and lifecycle analysis, only marginally understood a decade ago, have become common to the architect’s vernacular.

Today, these terms are being codified into a new canon of architectural standards. Perhaps the most widely recognized standards are those administered by the United States Green Building Council (USGBC), whose LEED (Leadership in Energy and Environmental Design) Green Building Rating System™ has gained primacy among governmental agencies, municipalities and major corporations eager to benefit from sustainable building.

The American Society for Testing and Materials (ASTM) also has established ASTM E 2129. This is another recognized standard designed to assess the “sustainability of elements or products” used in commercial and residential construction, as well as a building’s overall design efficiency, its impact on the habits of its occupants, and its influence on the surrounding climate.

The ASTM E 2129 standard addresses the potential environmental sustainability of a building project according to five major criteria, encompassing Materials, Manufacturing, Operational Performance of Installed Product, Indoor Environmental Quality and Corporate Environmental Policy. Rather than establishing specific standards within each of these categories, ASTM E 2129 poses a series of questions. Answers to those questions demonstrate to what degree a structure adheres to the principle of sustainable building.

While LEED does not certify individual building products, it does recognize that the selection of such products can play a vital role in making a building LEED compliant. PPG manufactures a variety of glass, paint and coating products that can help architects earn LEED certification for their projects. These products also positively address sustainability issues outlined in the ASTM E 2129 standard.

A Global Commitment
While the growth of green building is a relatively new phenomenon, PPG’s commitment to environmental responsibility is long-standing. For decades, PPG has been committed to making products and pursuing business practices that help sustain a healthy global environment.

In fact, most PPG building products transcend the LEED standard by addressing long-term economic, quality and manufacturing issues that impact the environment, yet fall outside LEED performance parameters. Many of these issues, such as corporate environmental policy, are addressed in the ASTM E 2129 standard.

On the corporate level, this commitment is articulated through PPG’s EHS (Environment, Health and Safety) policy, which fosters partnerships with governmental agencies and environmentally focused groups around the world. These partnerships support programs and meet strict standards for resource conservation, habitat preservation, and cleaner air and water.

A strong environmental awareness also pervades PPG’s research and product development efforts, which span numerous industries beyond the architectural field.

The result is a vast reservoir of technical knowledge and engineering expertise that enables PPG to translate the environmental advances it makes in one industry into exciting new products that serve another.

The Benefits are Clear
EcoLogical Glass for Architecture
Glass is one of the architects’ most versatile tools. Fused from raw materials that are abundant and inexpensive, glass is a low-maintenance material that has the capacity to retain or deflect the sun’s energy, while protecting building occupants from wind, rain, snow and other disruptive environmental forces.

Architects also treasure glass’s transparency, which can frame a dramatic view or present limitless color, shape and reflectivity options. Along with its decorative potential, architectural glass also performs two important functions that are critical to sustainable building, LEED and the ASTM E 2129 evaluation process.

Spectral Selectivity
For sustainable building projects, the ideal architectural glass is one that permits the greatest amount of natural light to enter a building while limiting, to the furthest extent possible, the thermal effects of infrared energy and solar heat gain.

A glass’s ability to balance this “spectral ideal” is quantified by its Light to Solar Gain ratio (LSG). Any glass that achieves an LSG of more than 1.25 is considered by the U.S. Department of Energy (DOE) to be . This designation became especially significant when the DOE, following a study by the Lawrence Berkeley National Laboratories (LBNL), recommended that all commercial buildings in the U.S. be glazed with spectrally selective glass.

Not surprisingly, PPG was a trailblazer in the development of these critical products more than 50 years ago. The company supplied the first spectrally selective glass to New York’s landmark Lever House Building in 1952, the first major skyscraper to use tinted glass as a design and environmental control element. PPG also made history 30 years later when it debuted the first Low-E coated product, Sungate® glass.

Today, the technologies that originated with these two products are industry standards. The glass featured on the Lever House Building, now known as Solexia™, is part of PPG’s inspiring Oceans of Color™ collection. With LSGs ranging from 1.28 to 1.34, Oceans of Color represents the world’s most unique and best performing line of spectrally selective tinted glasses.

Meanwhile, PPG’s original Sungate technology has evolved into two of the industry’s most effective and widely specified products, Solarban® 60 and Solarban® 80 Solar Control Low-E Glasses.

Solarban 60 Low-E Glass and PPG’s other low-emissivity architectural glass products are especially important to architects seeking to manage infrared heat gain while capitalizing on the benefits of natural daylight. These versatile, high-performance products can be combined with clear glass—or a complete range of earth- and ocean-inspired tints—to offer clients an unsurpassed selection of aesthetic and solar control capabilities.

Through their exceptional amalgamation of light transmittance and solar control engineering, PPG architectural glasses help architects satisfy LEED prerequisites in nearly every LEED environmental category, but especially those related to energy performance, daylighting and views, and thermal comfort.

The Glass is Always Greener
Lower heating and lighting costs aren’t the only way PPG glass enhances the environment. We’re making positive contributions through our manufacturing practices as well.

PPG was a leading pioneer in oxygen-fuel furnace technology and one of the first companies to install it on a float glass production line in North America. Today, this technology is in operation at two major PPG glass production facilities.

Thanks to this extraordinary advancement, PPG has cut the amount of fuel needed to make finished glass by more than 15 percent. Carbon dioxide emissions at these two plants also have been reduced by 10 percent and emissions of nitrogen oxide have been lowered by 50 percent. Finally, more than 70 tons of annual hazardous waste has been eliminated from the production cycle in these two facilities alone.

Recycling
Buildings also can earn LEED credits based on the amount of their recycled content. All PPG glass products contain a minimum 20 percent of post-industrial recycled glass. What’s more, every PPG glassmaking plant is equipped with extensive systems to recover and store discarded glass. Otherwise known as “cullet,” these materials are combined with other batch materials during the melting process. A full 100 percent of the unused glass PPG produces internally is recycled into production.

Finally, many of PPG’s glass products are shipped in reusable steel cases. As a result, the amount of disposable packaging that accompanies architectural glass products has been reduced from 75 percent to 10 percent.

Local Sourcing
PPG Certified Fabricator® Program
At least 20 percent of a project’s building materials must be manufactured within a 500-mile radius of the construction site, according to LEED mandates. ASTM E 2129 also advocates efforts to minimize the use of nonrenewable energy in the delivery of building products to the building site.

PPG’s Certified Fabricator® Program (CFP) is a network of highly trained and qualified suppliers with fabricating plants throughout the United States. They specialize in the fabrication of high-performance solar control and spectrally selective glasses, such as Solarban and Oceans of Color.

By purchasing glass from a local CFP, architects not only receive the highest possible level of quality and performance from their glass supplier, but they also can claim additional credit toward LEED certification, depending on the percentage of glass material used in their project.

Friday, November 28, 2008

Replacement Window Information For Building Professionals

The purpose of this blog will be to provide updated technical information about windows and glass technology on a timely basis. Many times new technology is released and building professionals don't hear about it in time to make better decisions.

Right now the replacement window industry is having a huge jump in energy efficiency and manufacturing technology. On the flip side, manufacturers that can't retool in order to compete are failing. Recently Kensington, a well known manufacturer, closed their doors. Unfortunately, we expect more window manufacturers and a large number of exterior remodeling companies to close their doors over the coming winter.

It's important that there is an industry source that can be counted on to distribute that kind of information. We hope to fill that role for many.

If you have any research requests or questions please feel free to email me. I look forward to helping.