Window Performance

WINDOWS

Performance

North Star windows are manufactured to guard against Canadian winters. The windows have been tested and certified by laboratories in both Canada and the United States. These tests have shown North Star windows to be so effective in keeping cold air out and warm air inside that they have earned the ability to use the Energy Star^® logo by the Department of Energy.

Why Do I Feel Cold Around My Windows?
There are three ways that windows can make you feel cold – Infiltration, Radiation, and Convection.

When the wind blows and air leaks in around your windows, this is called air infiltration. At some homes air infiltration is so bad that you can even see the curtains blowing in the wind. North Star’s double hung windows have a jamb stop that seals against the backside of the upper and lower sashes. This allows the addition of a third set of weather-stripping on the side of the sash. When the wind hits the outside of the sash, it has to make two right angle turns before it could ever reach the inside of the house. Look at other wood, vinyl, or aluminum windows. They do not have this jamb stop. Their weather-stripping on the side of the sash is the only barrier to air infiltration. It is a straight shot to the outside. These windows are missing this jamb stop.

When two objects are not the same temperature, nature moves heat from the warmer object to the colder object. This is a matter of physics. When your windows get cold during the winter, heat radiates from your warm body to the cold window. That’s why you feel cold or chilled when you sit next to a window. The warmer the glass temperature the less heat is transferred from your body to the window. Think about it, you don’t feel cold sitting next to that same window during the summer! North Star windows will make your glass warmer, because they come standard with Low-E glass and a non-metal Super Spacer between the pieces of glass. (Almost all insulated glass is made with a metal spacer. This metal transfers cold from the outside glass to the inside glass. This is what can make even new windows have cold glass and sweat.)

Even if the wind is not blowing, why do I feel air moving around my windows? Cold glass can create uncomfortable drafts or convection currents around your windows. As air next to a cold window is cooled, it drops to the floor. Warm air moves in to take the place of the air that has just dropped to the floor. The cold glass again cools the warm air. Now it drops to the floor. This process continues forming what is called a draft. This is why we say we feel air moving in a room even if there is no wind blowing outside. You can get this same feeling during the summer. Stand in your bare feet in front of the refrigerator and open the door, your feet feel cold. The cold air is falling out of the refrigerator and moving across your feet. You know there is no wind blowing out of the refrigerator. This is the same draft or convection current that is set up in your home during the winter when warm air is cooled by cold windows. You can eliminate these drafts by having warmer windows.

Lower Fuel Bills
The only reason the furnace turns on in the winter is to replace the heat that is lost. When cold air leaks in or heat radiates outside, the temperature in the house falls. If you never lost any heat during the winter, you could heat the house up once in the fall. The furnace would never have to turn on again. We can’t perfectly insulate our homes, but with North Star windows from DuHadway you can reduce how often the furnace runs. Designed for cold Canadian winters, North Star windows are different than other windows. They reduce air infiltration by the addition of the jamb stop. The glass temperature is warmer by using the non-metal Super Spacer and eliminating the cold metal spacer used by other companies to make insulated glass. These factors combine to make a well-insulated window that will make you and your pocket book more comfortable in the winter.

U-Values and R-Values
U-values measure the heat flow through a glazing system (glass of the windows). The lower the value the better the insulating quality. The R-value is the resistance of a material to heat flow. Higher R-values show the material has a better resistance to heat flow. U’s and R’s are different ways at looking at the same information. U’s are determined by dividing 1 by the R-value (U=1/R).

When trying to compare windows, homeowners often look for U or R ratings. While these numbers are important, you must understand how the rating was obtained since there is no standardized testing procedure.

Since over 80% of a window is glass, how the glass reduces heat transfer is very important. When listing U-values, window manufactures many times only show the U-values for the center of the glass in the sash. They do that because the center is the warmest part of the glass. This is the way to get the highest U-values. The only U-value that is truly important is the overall U-value. This rating takes into account the temperature at the center, but also measures the temperature at the edge of the glass. This is where the glass will be the coldest. The reason manufactures do not want to list this U-value is because it would show the effects of the metal spacers transferring cold at the edges. The lower temperatures on the edge of the glass would give lower U-value ratings. North Star using Super Spacer, non-metal structural foam, dramatically increases the edge temperature of the glass. By raising the edge temperature the center temperature is also raised. The whole window is warmer and feels warmer in the winter.

Ask DuHadway, an Energy Star® Partner, for windows that meet Energy Star Guidelines.

DuHadaway Corp.
2214 Wayne Trace | Fort Wayne, IN 46803 | 260.426.2000