With so many options available for windows selecting the type that best suits your needs can a complicated. We thought it would be an excellent opportunity to review the types of windows, what energy efficiency ratings really mean, and how the choice of window can affect your enjoyment of your log home.
Window styles find a place
Understanding the different styles of windows available can help you better plan where and what kind of windows to select.
- Double hung windows— The traditional type of window, they have upper and lower sashes that slide up and down vertically. A single hung window looks the same as a double but only one sash slides up and down. These windows require not extra interior or exterior clearance as the windows do not open in or out.
- Hinged windows— these windows come in several configurations and are hinged on one side to allow air flow to enter. An awning style window is hinged on the top, casement windows have the hinge on one side and hopper windows have the hinge on the bottom edge. A tilt and turn offers two actions and hinged areas, one on the side for opening and one hinge at the bottom that cal open the window like a hopper for ventilation. These windows require some consideration to clearance inside or outside. Windows that swing out should be avoided over walkways or decks, and may interfere with window treatments.
- Sliding windows— These windows slide back and forth like patio doors.
- Fixed windows—These don’t open at all and because they can be configured in many shapes offer lots of possibilities for adding light.
Windows and Heat
Windows transmit light and heat, both into and out of the home. Just how much is transmitted depends on the type of window, its orientation, its composition and energy rating. The climate your home is in will also determine the type of window may be the best suited for your home.
Homeowners in colder climates will want a window that transmits some of the solar heat into the room, while keeping heat from inside from escaping. Homeowners in warmer, sunny climates will expect their windows to minimize the solar heat transferred into the home while maximizing the insulation qualities of the windows to keep cooled air in. UV protection in the form of thin films can reflect harmful sunlight that can fade carpets and furniture.
Homeowners who select windows based on the solar exposure —north versus south—will also be able to brighten areas on the northern side of the home with more efficient glazing, while either blocking or transmitting passive solar energy in south-facing windows.
Airflow is a factor
Windows also offer an opportunity to improve airflow and ventilation in a home. By ensuring that a window is tightly sealed when closed with little leakage, unwanted infiltration of outside air can be controlled. But positioning windows to take advantage of cooling breezes when open can optimize airflow and save money in warmer months when the air conditioning can be turned off.
Anatomy of a window
Three elements of a window can affect its cost and performance: the window frame, the glazing and the insulation, including the spacers between the panes of glass and the weather stripping around the sashes.
Frames are the most visible part of the window and influence the overall cost of the window most dramatically.
- Aluminum frames are strong, durable and inexpensive. The aluminum conducts heat very well, so they can lead to significant heat loss in colder climates. They are best suited to mild desert climates or on impact resistant windows in hurricane zones.
- Vinyl frames are extruded polyvinylcloride (PVC) and have multiple chambers for rigidity that can also be filled with foam for extra insulation. They typically are made in lighter colors as darker colors can absorb enough heat to deform and degrade the vinyl.
- Wood frames moderately priced, and have good insulating value and structural strength. They require quite a bit of maintenance, with periodic cleaning and painting. They do allow a wide choice of colors, limited only by the paint chosen.
- Fiberglass frames are an excellent choice for climates that experience extremes of temperature. They offer maximum insulation, as fiberglass the least conductive material from which frames are constructed. Fiberglass frames require little maintenance and are durable and strong. As air temperatures change, the fiberglass expands and contracts at the same rate a the glass it surrounds, which prevents seals from failing.
Double- and triple-glazing in windows can create extra insulation by using airspaces in between the glass panes to slow the transmission of heat. To maximize the insulating factors, gases—either argon or krypton—replace air in these spaces. Thus the sealant qualities of the spacing materials between the panes of glass become essential in maintaining the integrity of the insulation. Spacers can be made of many materials, including aluminum, steel, fiberglass, foam or thermoplastics. Foam has the best insulation performance; aluminum the worst.
Weather stripping along the edges can affect how tightly the window closes and minimizes heat loss.
U-factors, performance ratings and new efficiency requirements
The National Fenestration Rating Council provides rating for windows sold in the U.S. U-factor calculates the overall insulating value of the components of the window. A lower number means better insulation and greater performance. The Solar Heat Gain Coefficient (SHGC) tells the percentage of solar heat that passes through the window, and a higher number can indicate the potential for solar heating gains.
Visible transmittance (VT) measures the amount of visible light that passes through the window with a value range of 0 to 1. A higher VT number would mean that more light would pass through and a good choice for windows that maximize daylight and views. Look for air leakage (AL) ratings below 0.3; lower is better. Finally condensation resistance is a relative scale of 0 to 100 that predicts the likelihood of condensation based on the windows properties. Here, higher numbers are better.
New federally mandated building codes (2009 IEEC) call for U-factors of 0.35 for zones 4-8 (northern half of the US with higher amounts for southern regions. Requirements for window SHGC are 0.30 for southern zones 1,2 and 3, and not required for northern zones 4-8. For additional 2009 IEEC information click here. [link to IEEC info on website here]
Katahdin offers Andersen windows that meet or exceed the new 2009 IEEC requirements as standard windows for our packages. Upgrades with additional UV protection and glazing are available. Your Katahdin dealer or representative can help you determine the most effective window configuration for your log home, land and climate.