Window Styles
Choosing Choosing The Right BC Window Style:
There are two main types of windows: those that open and those that don't. Those that open are called Operable and those that don't are called Fixed.
Fixed:
Fixed windows tend to be more energy efficient as they quite simply don't open and properly installed offer fewer opportunities for drafts.
Operable:
There are five main types of operable windows, Casements, Awnings, Hoppers, Sliders, and Tilt and Turn windows. Sliders can be further broken down into three main styles. Vertical Sliders that slide up from the bottom, Horizontal Sliders that slide from left to right or right to left and Double Hung Sliders that allow both the top to slide down and the bottom to slide up. Lets look at these in more detail.
Please choose from the following:
Operating Styles, Frame Types, The ABC's of Windows.
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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. Virtually the entire casement window area can be opened, while sliders are limited to less than half of the window area.
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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. Similar to casements, the entire window area can be opened, while sliders are limited to less than half of the window area.
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Hopper:
Hopper windows are hinged at the bottom and open inward. Hinged windows such as hoppers 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 exterior of the window unit. Similar to casements, the entire window area can be opened, while sliders are limited to less than half of the window area.
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Slider:
Both sashes slide horizontally in a double-sliding window. Only one sash slides in a single-sliding window. A Vertical Slider or Single Hung window, as it is also known, is identical to a Horizontal Slider but the bottom slides up. 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. Horizontally sliding windows generally have higher air leakage rates than projecting or hinged windows.
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Single and 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. Sliding windows, such as single- or double-hung units generally have higher air leakage rates than projecting or hinged windows.
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Tilt and Turn:
Tilt and turn windows employ special hinges that allow the sashes to tilt to the inside and turn to the inside. Typically they offer the most energy efficiency of all the window styles. They close like a fridge door. Because of their reinforced construction they can have very large opening and can even be made into French Doors.
Frames are particularly important since they can reduce the overall performance of the window. For example it was determined that standard double glazed aluminum framed windows weren't very efficient so in 1993 the National Building Code changed and the result was that they were eliminated. So it’s crucial that you consider both the materials and the design used. There are several frame materials to choose from. Let's look at the frame choices more closely.
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Aluminum:
Aluminum window frames are light, strong, durable, and easily extruded into the complex shapes required for window parts. Aluminum frames are available in anodized and factory-baked enamel finishes that are extremely durable and low-maintenance. The biggest disadvantage of aluminum as a window frame material is its high thermal conductance. It readily conducts heat, greatly raising the over all U-factor of a window unit. In cold climates, a simple aluminum frame can easily become cold enough to condense moisture or frost on the inside surfaces of window frames. Even more than the problem of heat loss, the condensation problem spurred has development of better insulating aluminum frames (see Aluminum with Thermal Break). In hot climates, where solar gain is often more important than conductive heat transfer, improving the insulating value of the frame can be much less important than using a higher-performance glazing system. It should also be mentioned that this type of frame, as of 1993, is no longer available.
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Aluminum Thermal Break:
Aluminum window frames are light, strong, durable, and easily extruded into the complex shapes required for window parts. Aluminum frames are available in anodized and factory-baked enamel finishes that are extremely durable and low-maintenance.
The biggest disadvantage of aluminum as a window frame material is its high thermal conductance. It readily conducts heat, greatly lowering the overall R value of a window unit. In cold climates, a simple aluminum frame can easily become cold enough to condense moisture or frost on the inside surfaces of window frames. Even more than the problem of heat loss, the condensation problem has spurred development of better insulating aluminum frames. The most common solution to the heat conduction problem of aluminum frames is to provide a "thermal break" Sby splitting the frame components into interior and exterior pieces and use a less conductive material to join them. Current technology with standard thermal breaks has increased the aluminum frame R value (heat loss rate) from roughly 2.0 to about 1.0 Btu/hr-sq. ft-°F. In hot climates, where solar gain is often more important than conductive heat transfer, improving the insulating value of the frame can be much less important than using a higher-performance glazing system.
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Vinyl:
Plastics are relative newcomers as window frame materials in North America. Vinyl, also known as polyvinyl chloride (PVC), is a very versatile plastic with good insulating value. Vinyl window frames do not require painting and have good moisture resistance. Because the color goes all the way through, there is no finish coat that can be damaged or deteriorate over time -- the surface is therefore maintenance-free. Some vinyl window manufacturers are now offering surface treatments like laminates (wood veneer, printable/stainable, maintenance free) and coatings. These products increase color selection and surface appearance options. Recent advances have improved dimensional stability and resistance to degradation from sunlight and temperature extremes. In terms of thermal performance, vinyl frames are comparable with wood, while there are minor differences, depending on the frame construction. Small hollow chambers within the frame reduces convection exchange, as does adding an insulating material.
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Wood:
The traditional window frame material is wood, because of its availability and ease of milling into the complex shapes required to make windows. Wood is favored in many residential applications because of its appearance and traditional place in house design. From a thermal point of view, wood-framed windows perform well with frame U-factors in the range of 0.3 to 0.5 Btu/hr-sq. ft-°F. Wood is not intrinsically the most durable window frame material, because of its susceptibility to rot, but well-built and well-maintained wood windows can have a very long life. Paint protects the exterior surface and allows an easy change in color schemes
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Wood Clad:
A variation of the wood-framed window is to clad the exterior face of the frame with either vinyl or aluminum, creating a permanent weather-resistant surface. Clad frames thus have lower maintenance requirements, while retaining the attractive wood finish on the interior. While vinyl and enameled metal claddings offer much longer protection to wood frames, they are generally available in a limited number of colors.
Images courtesy of the Efficient Windows Collaborative USA.
The ABC's of Windows:
Canadian Window and Door Manufacturers Association:
What ever window style you choose it's equally important to pick windows that have been certified by the Canadian Window and Door Manufacturers Association (CWDMA). That they meet or exceed the requirements under the National Building Code and that they are Energy Rated.
CWDMA Window Certification Program:
With the CWDMA Certification Program, Manufacturers undergo an in-plant quality control program and products are rigorously tested by accredited labs before certification is awarded. This is your assurance the products meet or exceed performance claims.
Energy Star® Ratings:
The first piece of information to look for on the label is the Energy Rating ( also referred to as the ER Rating ). The Energy Star® rating system for windows was developed by the Canadian Standards Association at the request of the Government of Canada and various energy utilities, and is now being used by manufactures.
The concept is simple. A windows energy rating is based on how mush heat comes in, and how much heat goes out, and the air leakage of the window.
A negative ER number means that the window loses more heat than it gains (expressed in watts per square meter). Most operating windows (windows that open and close) have a negative number because there is always some air leakage. However, some windows do have a positive number since they actually contribute heat to the house not only by taking advantage of solar energy, but also by having excellent frame and glazing unit designs.
The ER number can help you make the best energy efficiency decision. The ratings for single glazed windows are typically -17, for standard double glazed windows +3, and for typical double glazed Low E Argon filled windows +21 to +37.
