In assessing the "Green Rating" of a window product we must look at the total picture: Energy efficiency. resource efficiency (durability) and how the manufacturing process impacts the environment are three important points in determining how "Green" a product is.

Energy Retention and Loss
Windows have always been important in regard to energy efficiency. When looking at the "green" aspects of windows we must consider both heat loss and heat gain and not forget that windows allow access to daylight and fresh air. Windows with standard insulated glass have an insulating or "R" value of about 2.0. With new coatings and the addition of inert gasses window R values can reach 3.0 and beyond. The low-E coating on the outboard pane controls the loss of radiant heat from the building mass. By replacing the air between the panes with a less dense gas, argon, convection within the unit is slower, thus improving the thermal performance of the glass. Nevertheless, when we compare these numbers to the standard wall section with an R value of 13, it is easy to see where heat loss or gain through windows is critical to the building envelope. Therefore we must consider and apply all the latest improvements in glass technology to increase window performance.

Durability and Maintenance
The window material composition and exterior membrane are very important, especially in the green context. Products should be chosen for their longevity and ease of maintenance. The exterior surface should be resistant to the rigors of normal weather cycles (heat, cold, driving water, standing water) and harmful effects from the sun's ultraviolet rays. In recent years a few of the larger window manufacturers have been developing new materials from which window and door components can be fabricated. In some applications new materials are composed of recycled plastic and I or wood fibers mixed with resins. In other cases, new combinations of traditional materials like glass fibers are mixed with a high-tech resin and then pulled through a die to produce a new kind of material called a "pultrusion." By all accounts these new materials are stronger, lighter, and less thermally conductive than wood.

Environmental Impact
The use of new materials in the fabrication of windows versus the traditionally all-wood window has a positive side in relation to the environment. Quite simply, the demand for clear lumber has been reduced. But for most homeowners the warmth and beauty of real wood is still a very important element in the design of their home, and thus the demand for windows with wood interiors will remain for many years to come. Using engineered materials on the exterior protects the building and the window interior Itself from the elements. Many of these new window materials come from the factory with an extremely durable exterior finish already applied, so the need to use solvent-based paint or finishes in the field is reduced or eliminated.

High quality architectural coatings have been avail able for years, but some of the most resilient coatings have a negative environmental impact. Quite often the fabricating process itself is overlooked when judging the environmental impact of a particular product. In recent years, a few leaders in the industry have become very active in developing cleaner and more efficient manufacturing facilities. Inspired engineering has produced systems that recycle everything from water to plastic to scrap wood. At Marvin's new Integrity® plant engineers have developed a new system of finishing their product. The finish is applied using a flow coat process. After "Ultrex®" is drawn through a die (producing a pultrusion) it is passed through a liquid "curtain" of coating. The coating and pultrusion quickly cure together creating a unique bond. This process can be considered a green enhancement because more of the coating ends up on the intended part than in a conventional s pray painted process.

Environmental stewardship is the buzz term of the day. One of the biggest names in the window industry, Andersen has taken this role seriously by setting a positive example through aggressive waste management and drama tic reductions In TRI (Toxic Re lease Index). Active in the community as well. Andersen sponsors Eco Education and the Environmental Initiative Awards given annually by the Minnesota Environmental initiative. Answers to some basic questions provide a useful guide to selecting Windows in relation to the green criteria:

Environmental: Are the choice of materials and the fabrication process itself clean and "eco-friendly?" Does the company have a good track record for environmental stewards hip?

Quality: Are all the materials - the hardware, glass and exterior finishes of a high quality from a reputable company? Look for a minimum warranty of ten years on the glass, and where possible, on the entire unit.

Energy Efficiency: Does the window have a good energy rating from a reliable source (National Fenestration Rating Council or NFRC, Energy Star or National Wood Window and Door Association or NWWDA). Energy efficient windows reduce the use of fossil fuels, which saves on natural resources and reduces the emission of toxic elements into the atmosphere.