Better Daylighting

solera : Image Credit: Advanced Glazings, Ltd.Lighting for buildings is a major part of their energy use. Increasingly, green building design is recognizing the importance of providing natural daylight as a means of lighting the building and reducing energy use. Not only does natural daylight reduce the building's energy use, but it also increases comfort for the people in the building. The LEED system includes credit for providing at least 75% of the spaces in the building with natural lighting and views, and the credit is increased if 90% of the spaces are naturally lit.

Windows are good for providing views to the exterior. Skylights can be used to bring in more daylight, but they are not without issues. The problem with skylights is that they tend to create glare. The high contrast between areas where the daylight is streaming through the windows and other parts of the space that are not directly lit is visually (and sometimes even literally) uncomfortable. There's either too much light or too little. Diffuse light is more even and comfortable, and avoids areas of deep shadow and sharp glare. This is why so many older buildings had north oriented skylights or clerestory windows (or south-oriented in the southern hemisphere), and why those spaces were so well thought of as artists' spaces and galleries. The light quality is much better when it is from an indirect source.

Most diffuser options do little to spread the light around. Typical etched or frosted glass has little effect. The light patterns are a little bit softer edged from frosted glass than they are from clear glass, but when it is directly lit, it is little better than clear glass. Advanced Glazings, Ltd. offers much better performance for incorporating daylighting into buildings with a line of insulated glazing called Solera. Architects have known of Kalwall, another company that has been making translucent panels for many years. Kalwall is a panel of polyester and fiberglass that offers translucency and some insulation.

Like Kalwall, Solera is principally a commercial product. However, it is designed for use in standard 1" aluminum window frames (what you find in many offices, stores, and other commercial locations). High end home projects and experimental uses in residential uses are sure to follow. Since there are many manufacturers of aluminum window frames, it is easy for an architect to incorporate Solera into a project without creating complexity for the builder to have to deal with. Contractors like to use standard products that they are familiar with. Solera is also appealing because it uses glass, rather than plastic, which tends to yellow over time.

Even more exciting than the daylighting aspect alone, a new Solera unit is coming out that incorporates nanogel insulation. The 3" thick glazing unit has a specially shaped edge that allows it to be installed in a standard 1" frame. But the window will have an R value of around 20! A standard double glazed window typically has an R value around 1. And a typical insulated 2 x 4 stud wall has an R value of around 15. (Kalwall also offers a nanogel unit.) For most buildings, the windows are the weakest part of the energy envelope, where the greatest amount of energy was lost. Incorporating well insulated diffusing windows and skylights into a high performance building would provide exceptional energy performance in addition to daylighting.