As promised in last week’s GreenHouse, the second part of local sustainable architect Hyland Fisher’s advice on buying new windows for your home is appearing in this week’s column:
Part 2: “In last week’s article I discussed window frames. This week I will discuss different window-glass requirements, glazing options, orientation and treatments,” Fisher says. “This information applies when selecting windows for your new home or replacements for your existing home.
“Be sure to understand code requirements:
• Safety glazing (aka tempered glass) is required by code in certain locations, such as near stairs, doors and bathtubs. It is also required in new homes in Fire Hazard Severity Zones (e.g., forested areas).
• An emergency-egress (exit) window is required by code in all bedrooms. The window must be a certain size and minimum distance from the floor.
Glazing options to consider:
• The current window-glass standard is dual pane, low-e[missivity]. This option performs well and protects your interior finishes from sun damage. Higher performing triple pane, low-e windows are available but are more commonly used in colder climates.
• If you have a passive solar home, uncoated or ‘hard-coat’ low-e glass should be used in south-facing windows to heat the home in cooler months. Uncoated glass will provide the most solar gain; however, keep in mind it will not protect interior finishes from UV damage.
• ORNILUX is an innovative new window glass available to some window manufacturers. The glass is coated with a pattern that is practically invisible to humans but is visible to birds. This option significantly reduces bird-kills due to collisions with glass.
“Orientation and treatment considerations:
• It is critical to properly size your windows based on solar orientation. If done incorrectly, rooms may be too hot or cold, or they may be too dark or bright. Done correctly, the windows will help heat your home in the cooler months and provide the right amount of natural light.
• To minimize overheating in the warmer months, it is important to shade south- and west-facing windows. Properly located and sized exterior shading (e.g., trees, awnings, and overhangs) is more effective than interior shading (e.g., drapes, blinds).
“Finally, be sure that your windows are correctly flashed and caulked when they are installed. Water penetration and air infiltration are significant problems that can be avoided [see “Air-seal your home against the cold,” The GreenHouse, Jan. 17, 2013].”
