Windows 101

This page serves as your entry point to learning more about Replacement Windows. Browse through all the sections, or just a few. At any point feel free to Request a Quote.

Section I. Window Diagram
Section II. Common Types of Windows
Section III. Types of Materials Used in Replacement Windows
Section IV. Layers of Glass and Air Spaces
Section V. Types of Glass
Section VI. Window Rating Systems

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Window Diagram

1. Head -The main horizontal member forming the top of the window or door frame.
2. Jamb -The main vertical members forming the sides of a window or door frame.
3. Frame -The enclosure in which window sash or door panels are mounted.
4. Glazing Glass in a window or door; the act or process of fitting with glass.
5. Pane A - framed sheet of glass within a window.
6. Sash A - single assembly of stiles and rails made into a frame for holding glass.
7. Sill - The main horizontal member forming the bottom of the frame of a window or door.
8. Muntin Bar - Any small bar that divides a windows glass. Also called a grille or windowpane divider.

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Common Types of Windows Single-Hung/Double Hung

In double-hung units, both sashes slide vertically. Only the bottom sash slides upward in a single-hung window. Ventilation area can vary from a small crack to an opening of one-half the total glass area. Screens can be placed on the exterior or interior of the window unit.

Casement Casement windows are hinged at the sides. Hinged windows such as casements generally have lower air leakage rates than sliding windows from the same manufacturer because the sash closes by pressing against the frame. Casement windows project outward, providing significantly better ventilation than sliders of equal size. Because the sash protrudes from the plane of the wall, it can be controlled to catch passing breezes, but screens must be placed on the interior side.

Awning Awning windows are hinged at the top and open outward. Hinged windows such as awnings generally have lower air leakage rates than sliding windows from the same manufacturer because the sash closes by pressing against the frame. Screens are placed on the interior of the window unit.

Bay Window A bay window is made up of three or more windows. The side or flanker units project out from the building in 30, 45, or 90 degree angles. The center is parallel with building wall and is made up of one or more windows. All the units can be stationary, operating, or any combination thereof.

Bow Window A series of four or more adjoining window units, commonly five in number, installed on a radius from the wall of the building.

Fixed Frame Refers to windows that are non-venting or inoperable.

 

Skylight A window installed in a roof and assuming the same slope. Depending on which direction they face, skylights can bring in more light and heat than windows. For example, in the summer months, an unshaded south-facing skylight will bring in more direct sunlight and heat than a window. In a cold climate, a north-facing skylight gives almost five times more light than a north-facing window with almost the same amount of heat loss.

Slider Both sashes slide horizontally in a double-sliding window. Only one sash slides in a single-sliding window. Ventilation area can vary from a small crack to an opening of one-half the total glass area. Screens can be placed on the exterior or interior of the window unit.

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Types of Materials Used in Replacement Windows

Window frames are available in a variety of materials including aluminum, wood, vinyl, and fiberglass. Frames may be primarily composed of one material, or they may be a combination of different materials such as wood and vinyl. Each frame material has its advantages and disadvantages. Aluminum. Though ideal for customized window design, aluminum frames cause conductive heat loss (i.e., they have low R-values) and condensation. However, thermal breaks made of insulating plastic strips placed between the inside and outside of the frame and sash greatly improve the thermal resistance of aluminum frames. Wood. Wood produces higher R-values, are unaffected by temperature extremes, and are less prone to condensation, but they require considerable maintenance in the form of periodic painting. If wood frames are not properly protected from moisture, they can warp, crack, and stick. Vinyl. Vinyl windows are made primarily from polyvinyl chloride (pvc), which offers many advantages. They are available in a wide range of styles and shapes, have moderate to high R-values, are easily customized, are competitively priced, require low maintenance, and mold easily into almost any shape. Fiberglass. Fiberglass is relatively new and not yet widely available. They have the highest R-values of all frames; thus, they are excellent for insulating and will not warp, shrink, swell, rot, or corrode. Fiberglass frames can be made in a variety of colors and can hold large expanses of glass. Some fiberglass frames are hollow; others are filled with fiberglass insulation.

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Layers of Glass and Air Spaces Single-pane.

This has very little insulating value with (approximately r-1). It provides only a thin barrier to the outside and can account for considerable heat loss and gain. Double-pane. To improve a window's energy efficiency the number of glass panes in the unit is doubled, because multiple layers of glass increase the window's ability to resist heat flow.

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Types of Glass

There are various types of glass manufacturers use in constructing windows. Clear glass has been the primary material available for window panes in homes. However, in recent years, the market for glazing--or cutting and fitting window panes into frames--has changed significantly. Now several types of special glazing's are available that can help control heat loss and condensation. Low-emissivity (low-e) glass. This has a special surface coating to reduce heat transfer back through the window. These coatings reflect from 40% to 70% of the heat that is normally transmitted through clear glass, while allowing the full amount of light to pass through. Heat-absorbing glass. This contains special tints that allow it to absorb as much as 45% of the incoming solar energy, reducing heat gain. Some of the absorbed heat, however, passes through the window by conduction and re-radiation. Reflective glass. This has been coated with a reflective film and is useful in controlling solar heat gain during the summer. It also reduces the passage of light all year long, and, like heat-absorbing glass, it reduces solar transmittance.

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Rating Systems

There is now one predominant way to rate windows. You want to make sure that you are comparing windows that have been tested and measured in accordance with the National Fenestration Rating Council's (NFRC) 100-97 method. Most quality window manufacturers will "sticker" their windows. In other words, their windows will come with a simple, easy to read and understand sticker that has 2 values on it, U-factor and SHGC, also known as the Solar Heat Gain Coefficient. The result is what's known as a U-factor or value. If a window's U-value is low, it will lose less heat than one with a high U-value.

When comparing different windows, you should ensure that all U-values listed by manufacturers: (1) Are based upon the National Fenestration Rating Council's most recent testing guidelines (2) Are calculated for the entire window, including the frame, and not just for the center of the glass, and (3) Represent the same size and style of window from brand to brand.

The relationship you have with your contractor is an important one. You will want one who is qualified, trustworthy and capable of explaining the differences in various products and installations

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