Ask Sir Walter: Window Shopping Tips

Q: There are so many options when it comes to choosing windows. Why is it so complicated to save as much energy, hassle and money as possible? - Looking For A Clear View

A: Dear Looking For A Clear View:
It is easier than it seems to reduce energy loss, save money on your energy bills and eliminate the hassle of maintaining windows!

The right windows will block the energy flow out of or into your controlled indoor environment. Protect your indoor environment by choosing windows with the appropriate glass coatings, gas fillings, glass spacers and window frames for your climate. Here are a few things to keep in mind:

• Glazing: The sun emits visible light (VT), ultraviolet radiation (UV) and heat that are absorbed through the window. Glass coatings only allow specified wavelengths of energy to pass through.
• Gas Fillings: Added between the layers of glass, the gas filling reduces the conduction of the air space between the layers. Argon and krypton fills are common gases that show measurable improvements in thermal performance.
• Glass Spacers: More important for cooler climates, the spacer greatly affects the rate that heat will transfer through a window's edge. The less conductive the material, the better.
• Window Frames: The four most common frame types are wood, vinyl, fiberglass and aluminum.
  • Wood is usually the most eye-appealing. Wood-clad windows are also a great option.
  • Vinyl continues to grow in popularity. This material is energy-efficient and very durable.
  • Fiberglass frames are relatively new to the market. They are very strong and expand well for less air leakage.
  • Aluminum windows are light, tough and low maintenance. However, they are generally not as energy-efficient.

The best tool you can use to compare window performance is the National Fenestration Rating Council (NFRC) label. The information on this label is produced in a certified NFRC lab that has simulated the entire performance of the window. There are four areas measured on this label:

• U-Factor determines how well a product prevents heat from escaping. U-Factor ratings generally fall between 0.20 and 1.20. The lower the U-value, the greater a window's resistance to heat flow and the better its insulating values.
• Solar Heat Gain Coefficient (SHGC) surveys how well a window blocks heat caused by sunlight. SHGC is expressed as a number between 0 and 1. The lower a window's solar heat gain coefficient, the less solar heat it transmits.
• Visible Transmittance (VT) gauges how much light comes through a product. VT is expressed as a number between 0 and 1. The higher the VT, the more natural light in your home.
• Air Leakage is an optional measurement. Air Leakage (AL) is indicated by an air leakage rating expressed as the equivalent cubic feet of air passing through a square foot of window area (cfm/sq ft). The lower the AL, the less air will pass through cracks in the window assembly.

You can also find the NFRC information on any existing window by locating the small, permanent NFRC serial code etched on an inconspicuous part of the window. By providing this number to the NFRC, you will be able to determine that window's level of performance.

Best regards,
Sir Walter Lindal

If you have further window-related or other home building questions, click here to get a personal response from Sir Walter.

To view samples, options and the NFRC ratings of Lindal windows, visit your local Lindal dealer. There you will see some of the finest windows available, including cedar windows, wood clad and high performance vinyl. All of these Lindal windows have earned the Energy Star label.