Technologies for Energy Efficiency

Professionals have many choices for the delivery of energy-efficient solutions to their clients, from harnessing the sun for solar hot water, to providing options for indoor air delivery and using energy-efficient windows.
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Sponsored by Heliodyne, Milgard Windows & Doors, The Modern Fan Co., Tate Access Floors
Celeste Allen Novak AIA, LEED AP

Standards and LEED® credits

The purpose of the Solar Rating and Certification Corporation is "to administer a certification, rating, and labeling program for solar collectors and a similar program for complete solar water heating systems."8 Solar collectors are tested for wind load, hail, structural stability as well as thermal performance by third party testing laboratories. They provide guidelines on the use of PEX, sizing, component substitutions and installations. Manufacturers have performance ratings of their collectors certified by the SRRC.

ENERGY STAR provides a list of approved solar water heaters that are eligible for tax credits.9 Tax credits are available to consumers at 30 percent of the cost, with no upper limit for the purchase and installaton of an approved solar hot water heating system through 2016 for both existing and new homes. The credit is not availale for heating a swimming pool or a hot tub, it is meant to offset the heating for domestic use in the home.10 For residential installations, there can be a good rate of return on the homeowner's investment. With the included Federal tax credit, most homeowners can expect to recoup their investments within eleven years or less.

It is not as easy to predict the ROI on commercial installations. In the home, or in a small hot water system, professionals report savings as much as 80 percent off of their water heating bill in Hawaii, a warm, sunny climate, to 50 percent in Alaska. According to Heliodyne's Pilgaard, "The professional should find the balance between the size of the system and the offset savings. To analyze what is correct, the bigger system might not be the best investment."

In LEED® 2009, professionals can receive credits in many categories. Solar hot water is a renewable energy system that with the rising cost of fuel, particularly in sunny climates, makes sense as a primary tool for energy savings.

PROVIDING ACCESS TO DAYLIGHT AND THREE- DIMENSIONAL WINDOW DESIGN

Recognizing the environmental impact of energy-efficient windows is a good part of designing an energy-efficient building envelope. An energy-efficient window is a synergy of its components. Maureen Faccia identified these components as the "three dimensions of energy-efficient window design." These include the glass, spacer and the frame. The professional should choose a window that has good performance in all of these dimensions.

Glass, Spacer, Frames

Single-pane, double-pane and triple-pane - windows can be chosen with many types of glazing. Maureen Faccia recommends that professionals log into a web tool provided by the Efficient Windows Collaborative.11 This site was developed jointly by the Center for Sustainable Building Research, at the University of Minnesota, the Alliance to Save Energy and the Lawrence Berkeley Lab and provides descriptions of how energy-efficient windows work, information on building codes and numerous resources for manufacturers as well as for the professional. In order to compare costs for a typical house, a map of the United States broken into four climate zones is provided and by selecting on a city nearest to your location, the annual energy use from computer simulations for a typical house in your city can be compared for different window options.12

Diagram of the three dimensions of window design that includes the glass, spacer and frame.

Photo courtesy of Milgard Windows & Doors

The glazing in a window means the difference between keeping cool in the summer and warm in the winter, reduces condensation and protects finishes and furniture from fading from the sun's rays. Dual-pane designs use an air- or gas-filled space between two panes of glass. This insulates much better than a single pane. Special Low-E coating on the glass blocks infrared light and filters damaging ultraviolet light (UV). ENERGY STAR describes the anatomy of an energy-efficient window13 and labels those windows which meet set energy performance criteria. The ENERGY STAR label is an independent third party certification from the National Fenestration Rating Council (NFRC). U-factors, or the rate of heat transfer, generally range from .0.25 to 1.25 and ENERGY STAR also provides a map with four climate zones for selecting the appropriate U-factor for your region, identifying approximate dollar savings per region.14 Choosing a Low-E glass contributes to energy savings by deflecting heat before it enters the occupied zones of a building.

Additional NFRC ratings are provided for the Solar Heat Gain Coefficient, Visible Transmittance, Air Leakage, and Condensation Resistance. Windows are rated with respect to performance of the glass within the unit. Insulating spacers between the panes of glass reduce heat transfer and prevents condensation. Early single-paned windows in metal frames had to be scraped of frost on the inside to peer out into a cold winter day in the 1950's. Condensation in southern climates, warped wood frames and provided a breeding ground for mold and mildew. A spacer keeps a window's dual-glass panes the correct distance apart for optimal airflow between panes. Too much or too little airflow can affect the insulating glass efficiency. The design and material of the spacer also can make a big difference in the ability to handle expansion and contraction and thus reducing condensation.

Along with performance, one of the most important aesthetic decisions to make when choosing a window is the frame. A window frame holds the sash or casement and window hardware. A properly designed frame helps minimize thermal transfer throught the window. Engineered for performance, new vinyl and fiberglass frames are available with chambers within the frame that enhance strength, noise reduction and have a greater insulation value. These frames provide a wide palette of colors, and design styles.

According to the Denver AIA Committee on the Environment, in the Sustainable Design Resource Guide, "Fiberglass frames have a low embodied energy, their thermal performance is comparable to wood and vinyl, and it is durable and maintenance free. The cost is presently comparable to a good wood window. More common are fiberglass doors with insulating cores which perform as well thermally as steel insulating doors."15 Fiberglass frames are available for both commercial and residential projects. Pultruded fiberglass window frames are manufactured from raw materials that include liquid resin, fillers, specialized additives and reinforced fibers. This process also uses limited natural resources. Based on product longevity and its low pollution levels during manufacturing, in 2007, the EPA labeled pultruded fiberglass environmentally friendly. Professionals can address energy efficiency, sustainability and green through producst as well as processes by choosing a fiberglass frame for energy-efficient windows.

 

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Originally published in GreenSource
Originally published in July 2009

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