Safety & Energy Articles from FEC

The Rural Missouri NEWS Service
Jim McCarty 573-635-6857, ext. 3402

July 2008

Can We Talk (About Energy)?

Do you know what’s going on with energy today? If not, we need to talk. As a member-owner of an electric cooperative, you need to know what is driving up the price you will pay for the electricity you use.

Your electric cooperative is working hard to start a national dialogue about energy and the future. That dialogue needs to take place between your cooperative and its members, and between those members and
the people elected to represent them in the state and federal governments. Already electric rates are on the
rise for a variety of reasons:

The price for fuel to generate electricity - coal and natural gas - is increasing.
Environmental legislation requires adding emission control equipment that is costing millions to construct and operate.
Increased demand for electricity from larger homes and more members means low-cost power must be supplemented with higher-cost peaking units to meet demand.
That increased demand means more power plants must be built, and these plants will be extremely expensive.
To move that power where it’s needed, more transmission lines must be built and existing ones must be upgraded.

While these factors are pushing rates higher, another issue looms on the horizon that has the potential to make electricity unaffordable for most Americans. Congress is now considering legislation that will limit emissions of carbon dioxide in response to claims that this gas is contributing to global warming. Since carbon dioxide is released from both coal and natural gas fueled power plants, it is easy to see that any limits on emissions will lead to higher generation costs.

Your electric cooperative believes Congress can solve the climate change problem without breaking the economy. To do this, however, will require major investment into new technology. It will also take a balanced approach to providing electricity, using coal, natural gas, nuclear, hydro, wind and other renewable resources. No single source of power will meet the goals of ensuring an adequate supply of electricity at rates consumers can afford.

As Congress debates energy policy in a carbon constrained world, we need your help to ensure they get it right. Future generations depend on this. You can make a difference. If you have Internet access, log on to www.ourenergy.coop and follow the steps to send an e-mail to your elected officials. If you don’t have Internet
access, contact your electric cooperative and we will do it for you. As we talk about our energy future, we won’t be debating whether global warming is a reality or what source of electricity is the best. Instead, we are asking our elected officials to ensure the United States will continue to have dependable, affordable electricity for all.

Efficient Window Primer

The windows of your home are like the eyes in your face. They express the character of the house. They admit light to brighten and warm the interior of your house. They provide natural ventilation. They allow you to view the outside world without stepping outside into drenching rain, a blizzard or intense humidity. In centuries past, citizens were taxed based on the number of glassed windows, so windows of any kind became a status
symbol of sorts. Even today, rooms and offices with windows are still highly valued.

In these times of enhanced energy consciousness, however, inefficient windows can be a huge energy drain. If you have single-pane windows without weatherstripping or caulking, without screens or awnings, you might as well leave your front door wide open. The loss of energy through inefficient windows can be that bad. In winter,
windows may account for up to 30 percent of a home’s total heat loss, according to the University of Missouri Extension.

Fortunately, there are many things you can do to make existing windows more efficient and reduce your energy bills. And if you’re ready to replace old windows, you may be surprised at how efficient panes of glass have become. One resource to check out is Residential Windows: A Guide to New Technology and Energy Performance, available at www.amazon.com or from bookstores. This book was supported by the U.S. Department of Energy, Lawrence Berkeley National Laboratory and Oak Ridge National Laboratory. It covers window installation, energy efficiency and building codes and is an essential resource for anyone considering purchasing or installing new windows.

Know your windows: a glossary of window terms

The National Fenestration Rating Council (NFRC) is a nonprofit organization that tests, certifies and labels windows, doors and skylights based on their energy-performance ratings. At www.nfrc.org, you will find a handy glossary for understanding window terminology. The site includes a sample label that provides a reliable way to determine a window’s energy properties.

U-factor – A measurement of how well glass prevents heat from escaping. Ratings generally fall between 0.20
and 1.20. The lower the U-factor, the better the glass is at keeping heat in. Note that U-factor doesn’t apply to the frame and weatherstripping around the glass, which can lose a great deal of heat if not tightly fitted or properly applied.

Solar heat gain coefficient (SHGC) – A measurement of how well a window blocks heat from the sun. SHGC is expressed as a number between 0 and 1. The lower the SHGC, the better a window is in blocking unwanted heat gain, particularly important during the summer. In winter, of course, you want maximum heat gain from south-facing windows.

Condensation resistance (CR) – A measurement of how well a window resists condensation. CR is expressed as a number between 1 and 100. The higher the number, the better a product is able to resist condensation. Not all manufacturers include this rating on their labels.

Air leakage (AL) or infiltration – A measurement of how much outside air comes into a building through a window. AL rates typically fall between 0.1 and 0.3. The lower the AL, the better a window is at keeping air out. Not all manufacturers include this rating on their labels.

Visible transmittance (VT) - A measurement of how much light comes through a window. VT is expressed as a number between 0 and 1. The higher the VT, the higher the potential for daylighting.

How windows block heat

Paul Fisette, director of the Building Materials Technology and Management Program at the University of Massachusetts, writes in a Fine Homebuilding article about how windows lose and gain heat in four ways. This heat transfer is expressed in U-values or U-factors. The lower the U-value, the higher the insulating value.

Conduction is the movement of heat through a solid material. Touch a hot skillet, and you feel heat conducted from the stove through the pan. The same process occurs in a window. By introducing less conductive material into a window, you impede heat flow. Multiple-glazed windows contain low-conductance gas such
as argon between panes of glass. Thermally resistant edge spacers and window frames can reduce conduction, too.

Convection occurs when heated indoor air rubs against the interior surface of window glass. The air cools and drops to the floor. Warm air rushes in to take its place on the glass. This convective loop is self-perpetuating
and feels like a cold draft. The temptation is to turn up the heat (each 1 degree Fahrenheit increases energy use 2 percent). Multiple panes of glass separated by low-conductance gas and good edge spacers, combined with thermally resistant frames, raise interior glass temperatures, slow convection and improve comfort.

Radiation is the movement of heat as long-wave heat energy from a warmer body to a cooler body. Stand near a woodstove, and you experience radiant transfer. Clear glass absorbs heat and re-radiates it outdoors. Radiant-heat loss through windows can be greatly reduced by placing low-e coatings on glass that reflect specific wavelengths of energy.

Air leaks siphon about half of an average home’s heating and cooling energy to the outdoors. Much of this
occurs through windows. Well-designed windows have durable weatherstripping and high-quality closing devices that effectively block air leakage. Hinged windows such as casements and awnings clamp more tightly against weatherstripping than do double-hung windows. How well the individual pieces of the window unit are joined together also affects air leakage. Glass-to-frame, frame-to-frame and sash-to-frame connections must be tight. The technical specifications for windows list values for air leakage as cubic feet per minute per square foot of window. Look for windows with certified air-leakage rates of less than 0.30. Lowest values are best.

Glass: it isn’t what it used to be

The Missouri Department of Natural Resources (DNR) points out that until recently conventional, clear glass was the primary material for residential windows. Now, several types of special glass are available that can help control heat loss or gain, thereby reducing the amount of energy used for heating or cooling.

Low-emissivity (low-e) glass – This glass has a special coating that admits the full spectrum of sunlight but blocks radiant heat from escaping. While the air space in normal double-paned windows reduces some of the heat loss, a significant amount of heat is transferred from the warm inner pane to the colder outer pane. Coatings on low-e glass reduce the emissivity and increase the R-value (resistance to heat flow) of double-paned units. The incoming visible light is reflected only slightly, so low-e glass appears almost clear rather than mirror-like. Windows with low-e coatings cost about 10 percent to 15 percent more but can reduce
energy flow by 30 percent to 50 percent.

DNR recommends new windows be the low-e type with a U-value (conductance of heat) of .35 or less to control conduction losses. The windows also should have a shading coefficient of .5 or less to control radiant heat gain in the summer. (Shading coefficient, which measures the effectiveness of a shading device, is being phased out in favor of solar heat gain coefficient (SHGC). Shading coefficient is about equal to SHGC multiplied by 1.15.) If a large expanse of glass is used on the south side for solar heating, then a shading coefficient approaching 1.00 should be used for these windows with the radiant heat gain controlled with shades or awnings or both.

Heat-absorbing glass – Special tints in this more expensive glass allow it to absorb as much as 45 percent of the incoming solar energy, reducing heat gain. Part of the absorbed heat, however, will continue to pass into the structure. An inner layer of regular glass reduces this transfer. Heat-absorbing glass reflects only a small percentage of visible light and, therefore, does not have the mirror-like appearance of reflective glass.

Reflective glass – This glass is coated with a reflective film. It controls solar heat gain during the summer, but
it also reduces the passage of light all year long and, like heat-absorbing glass, reduces solar transmittance in winter. Heat-absorbing glass and reflective glass should not be used in passive solar heating applications, such as south-facing windows.

What about retrofitting windows?

If your son slams a baseball into your house, shattering a pane of glass but not the entire window, does it make sense to replace the entire window or just the pane? The answer depends, but if the window frame is in good shape and doesn’t leak, then retrofitting a pane into the existing frame is probably the way to go. However, Bill and Kevin Burnett in an article on www.doityourself.com caution that retrofitting steel casement type windows used in the 1950s or the aluminum windows used in the 1960s, 1970s and 1980s should be done only when you’re convinced the installer can make the retrofit airtight.

Retrofitting the double-hung wooden windows common in older houses requires removing the sash and attaching the new window unit to the old wood frames with shims and screws. If properly installed and joints are caulked, this type of retrofit can be airtight. Note, though, that retrofitting new glass into old frames to
save electricity won’t result in a quick payback.

Save $ on your power bill with existing windows

Double-pane windows cost about twice as much as single-pane but pay for themselves in decreased energy
costs. But if you can’t afford to replace your single-pane windows, the Missouri Department of Natural Resources (DNR) offers these inexpensive alternatives that will save you energy dollars:

Storm windows – For homes with single-pane windows, storm windows can sometimes be even more effective in blocking heat transfer than double-paned windows. The least expensive type of storm window is plastic sheeting installed outside or better yet inside the windows. More expensive glass storm windows with wood, metal or vinyl frames can be attached to the window frame with clips or screws. Storm windows over single-pane glass can save 50 percent of heating losses through the window. How much can you save with storm windows? DNR estimates payback ranges from several months to a year for plastic sheeting to five to 10 years for glass.
Window treatments – Insulating shades, shutters and drapes provide some insulation to windows in the winter by reducing heat loss at night and allowing sunlight in during the day. Tight-fitting plasticized roller shades or Roman shades also can reduce heat loss through single-pane windows. When choosing a more elaborate window covering, select a tightly woven fabric with separate or reflective lining. A cornice over the top of the draperies will prevent a draft tunnel effect. Mini-blinds are effective for light control but may not reduce solar gain. In summer, keep windows closed and covered during the hottest hours of the day. On overcast winter days and at night, keep shades and draperies closed; open them on sunny days to take advantage of solar gain.
Shading devices – Awnings, exterior shutters or screens can be used to reduce unwanted heat gain in summer.
Reflective films – This treatment reflects sunlight away from windows and reflects heat back into the room.
Caulking and weatherstripping – These inexpensive methods stop air leaks around windows and can be applied by most homeowners themselves. In older houses and historic houses, replace window glazings that are cracked.

Moisture on windows: what to do

It’s difficult to completely eliminate moisture on windows. Single-pane windows with metal frames or high moisture with inadequate ventilation can result in condensation, frost or pools of water on windows and sills. Such condensation can rot wood and lead to mold and mildew. Here’s what Energy Star recommends for fixing the problem:

Use ventilation fans in kitchens and baths to control moisture
Vent your clothes dryer directly outside, where possible
Install storm windows over single-pane windows, especially with metal frames – or replace them with
energy-efficient windows
Install a shrink film or polyethylene sheet, window insulation kit from a home center or hardware store if you can’t afford storm windows or new windows
In winter, check your humidifier to make sure it’s not adding too much moisture to your indoor air; 30 percent to 50 percent interior humidity is recommended; use a dehumidifier if higher

Anatomy of an energy-efficient window

Energy Star offers this analysis of efficient window components:

Improved frame materials – Wood composites, vinyl and fiberglass frames reduce heat transfer and help insulate better.
Low-e glass – Special coatings reflect infrared light, keeping heat inside in winter and outside in summer. They also reflect damaging ultraviolet light, which helps protect interior furnishings from fading.
Gas fills – Some energy-efficient windows have argon, krypton or other gases between the panes. These odorless, colorless, nontoxic gases insulate better than regular air. Gas-filled windows are more expensive, and over 10 years, the gas may leak out.
Warm-edge spacers – A spacer keeps a window’s glass panes the correct distance apart. Today’s warm edge spacers – made of steel, foam, fiberglass or vinyl – reduce heat flow and prevent condensation.
Multiple panes – Two panes of glass, with an air or gas-filled space in the middle, insulate much better than a single pane. Some Energy Star-qualified windows have three or more panes for even greater efficiency, increased impact resistance and sound insulation.

Energy-saving tips for windows

Energy Star offers these energy-saving tips for windows that will reduce your energy use:

Proper installation – Have your windows installed by trained professionals following the manufacturer’s instructions. Otherwise, your warranty may be void.
Window orientation – When building a new home, renovating or planning a major addition, orient as many windows as possible to the south and use roof overhangs to shade windows on the east and west from the sun in summer. Overhangs are much less effective against the lower angles of the east and west sun. Therefore, reduce the size and number of east- and west-facing windows to reduce energy use.
Plant a tree – Strategically planting deciduous trees near south-, east- and west-facing windows will provide needed shade in the summer but let in the sun’s heat during winter.
Home sealing – If you add up all the hidden air leaks in your home, they can equal a hole the size of an open window. To maximize home efficiency, seal all the gaps where air can leak in or out, including those around windows.

What to look for when buying new windows

The U.S. Department of Energy offers a comprehensive window checklist that covers insulating value and
condensation resistance, solar control and ultraviolet protection; daylight and view; ventilation and air-tightness; sound control; privacy, safety and security; maintenance, durability and lifetime; installation; and economics. Here’s a sampling of some key points:

Insulating value and condensation resistance

Look for the National Fenestration Rating Council’s U-factor ratings and labels to guide window selection
Select double-pane windows in all climates where heating is needed; select double- or triple-pane windows with low-e coatings and gas fills (argon, for example) in cold climates to reduce heat losses and condensation; low-e refers to glass with an invisible coating that admits the full spectrum of sunlight but blocks radiant heat from escaping
To reduce frame and edge heat losses and condensation in all climates where heating is needed, select windows with wood; vinyl; fiberglass; or properly designed, thermally broken aluminum frames; the latter refers to frames that include a thermal barrier that resists the transfer of cold air in winter to the inside of your house and slows the transfer of heat in summer
Use heavy drapes, thermal shades or thermal shutters to provide additional window insulation in cold climates

Solar control and ultraviolet protection

Look for NFRC solar heat gain coefficient ratings and labels to guide window selection; Look for low U-factors, low solar heat gain coefficients, high condensation resistance, low air leakage and low visible transmittance
Select windows with special tints or modified low-e coatings to reduce solar heat gains while maintaining high visible transmittance
Select tinted windows to reduce solar heat gains and control glare by lowering visible transmittance
Select special glazings to reduce ultraviolet transmission in rooms with furniture, carpets, drapes and pictures subject to fading
Select exterior shading devices to minimize the inward flow of absorbed solar heat
Select interior shading devices to reduce solar heat gains while providing for privacy and aesthetics
Select external horizontally oriented shading devices for south-facing windows and external vertically oriented shading devices for east- and west-facing windows
Use overhangs, exterior awnings or deciduous trees and shrubs to shade east-, west- and south-facing windows during the summer, while allowing beneficial solar heat gains during the winter

Ventilation and air-tightness

Select operable windows for rooms requiring substantial ventilation during mild weather and to meet building code egress requirements
Select casement or awning windows to maximize effective ventilation area
Select awning windows to better exclude precipitation while ventilating
Position operable windows in opposite walls of living spaces to maximize cross ventilation
Select fixed windows or windows with compression seals to minimize infiltration
Select windows and skylights with continuous edge seals to minimize infiltration
Seal and caulk around windows and skylight frames and sash to reduce infiltration

Selecting energy-efficient windows in Missouri

The International Energy Conservation Code (IECC) is a national model energy standard certified by the U.S. Department of Energy. In Missouri, the IECC assigns counties into Climate Zone 5 and Climate Zone 4 and sets efficiency requirements for windows in new buildings, remodeling and additions to existing buildings accordingly. You may download the requirements at the Efficient Windows Collaborative Web site at http://www.efficientwindows.org/codes2006/Missouri.pdf.

The following Missouri counties are assigned to Climate Zone 5: Adair, Andrew, Atchison, Buchanan, Caldwell, Chariton, Clark, Clinton, Daviess, De Kalb, Gentry, Grundy, Harrison, Holt, Knox, Lewis, Linn, Livingston, Macon, Marion, Mercer, Nodaway, Pike, Putnam, Ralls, Schuyler, Scotland, Shelby, Sullivan and Worth. All others are in Zone 4.

Tips to improve window efficiency summer and winter

The University of Missouri Extension offers a comprehensive guide on Shades and Shutters for Energy Efficiency (#GH2815) that you can download from http://extension.missouri.edu/explore/hesguide/intdes/gh2815.htm. It includes suggestions for improving the efficiency of your windows.

Summer – Close all window coverings during hours the air conditioner is operating. If the air conditioner is not in use, close those windows and window treatments receiving direct sunlight. Use shaded windows for ventilation.

Winter – In winter, there are about 16 hours a day when windows aren’t performing their intended function. Instead, they are enormous heat drains. Here’s how to maximize their efficiency:

South windows – Open the window treatment for the six best hours of sunshine. These windows gain more
heat during the day than they lose at night. Night insulation is very effective.
East and west windows – Open the window treatment for the three best hours of sunshine. Solar heat is gained through east windows during morning hours and through west windows in late afternoon.
North windows – Close unless there is sun in morning or evening. North windows receive no direct sunlight
and are always losing heat.

Cover those windows!

How much difference do window shades and shutters make in energy efficiency? The University of Missouri Extension provides some convincing evidence that it’s worth the investment in its comprehensive guide on Shades and Shutters for Energy Efficiency (#GH2815) that you can download from http://extension.missouri.edu/explore/hesguide/houseeq/gh4882.htm.

As it points out, a single-glazed window has an R-value (resistance to heat flow) of about 1 and a double-glazed window or a window with a storm window of about 2. In other words, 10 to 20 times more heat escapes through each square foot of window than through an insulated wall with an R-value of R-19 in Missouri. Extension states that window coverings with an R-value of 4 are considered cost-effective because they stop about 75 percent of heat loss. Here are more specifics from Extension:

Type of window or treatment & R-value

Single glazing, bare; 0.8-1.0
Double glazing, bare; 1.8-2.0
Single glazing, loose drapery; 1.10
Double glazing, pulled shade; 2.05
Double glazing, sealed drapery; 2.35
Double glazing, insulated shutters; 9.50 or more
Double glazing, insulated quilt, one layer polyester fiberfill; 4.55
Double glazing, insulated quilt, three layers of polyester; fiberfill 6.75

No current tax credits for windows

As of Dec. 31, 2007, most of the residential tax credits (windows, doors, roofs, insulation, HVAC, and non-solar water heaters) expired. On Feb. 27, 2008, the U.S. House of Representatives passed $18.1 billion in renewable energy tax incentives (H.R. 5351), including an extension of the tax credit for energy-efficient home improvements. H.R. 5351 must still pass in the Senate and be signed by the President to become law. Missouri currently offers no tax credits for windows.

Useful Web sites for windows

http://extension.missouri.edu/explore/hesguide/intdes/gh2815.htm - Download or buy the University of Missouri Extension’s GH2815, Shades and Shutters for Energy Efficiency, for information on reducing heat loss through window management. Also look for GH4882, Home Energy Management: Weatherstripping Your Windows,” at http://extension.missouri.edu/explore/hesguide/houseeq/gh4882.htm.
www.nfrc.org - The National Fenestration Rating Council offers a series of guides on replacement windows, daylighting and visible transmittance, windows and condensation, energy efficient windows, solar heat gain and windows and windows and heat loss.
http://www.eere.energy.gov/buildings/info/documents/pdfs/window_selection-777.pdf - Download the guide on Window Selection from the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy Web site. Other sections of this site include information on selecting new windows and replacement windows and energy ratings for windows.
http://www.dnr.mo.gov/energy/residential/windows.htm - The Missouri Department of Natural Resources offers much useful window information, specific to Missouri, as well as links to other Web sites about windows.
www.energystar.gov - Information on the Environmental Protection Agency’s Energy Star windows to help consumers identify efficient windows, doors and skylights.
www.efficientwindows.org - The Efficient Windows Collaborative promotes the manufacturing and usage of energy-efficient windows, doors and skylights. It provides information on the benefits of energy efficient windows, descriptions of how they work and recommendations for their selection and use.

Return to Top

PRINT THIS WINDOW
CLOSE THIS WINDOW