Frequently Asked Questions

Q. What is “Low E” glass?

A: Low E glass products give you year round energy savings and comfort by helping manage the sun’s energy and the heating system energy in your home. Low E glass products are coated with microscopically thin, optically transparent layers of silver sandwiched between layers of antireflective metal oxide coatings. In the summer, Low E glass products let in visible sunlight while blocking infrared and ultraviolet solar energy that drives up cooling costs and damages curtains, window treatments, carpeting and furnishings. And in the winter, Low E glass products offer greater confort and reduced heating costs by reflecting room side heat back into the room. Emissivity is a measure of how much heat is emitted from an object by radiation. Heat is transferred to and from objects through three processes: conduction, convection and radiation. For instance, on a hot night, heat will be conducted through a window from the outside, causing the inside pane to become warm.

Convection, or natural circulation, of the air in the room pst the window will transfer some of the heat into the room. But the window will also radiate heat as infared waves, which will harm objects throughout the room. The radiative heating is why you can feel the red-hot piece of metal (for instance, a heating element on an electric stove) from several feet away. Low-emissivity, or low-e, coatings are put on windows to reduce the amount of heat they give off through radiation. In hot climates, where the outside of the window will typically be hotter than the inside, low-e coatings work best on the interior of the outside window pane. In cold climates, where the inside of the window is typically hotter than the outside, the low-e coatings work best on the inside window pane, on the side that faces toward the outside

Q: What is U-Value?

A: The U-Value, also called the U –factor, is a measure of how well heat flows through an object (thermal conductivity) it is also referred to as the heat transfer coefficient of heat transmission. The U-Value is measured by how much heat (Btu) flows through a certain area (a square foot) each hour for a certain temperature difference(° F) , so it is measured in bru/ft2-hr-°F. The U-value is the reciprocal of the R-value: the lower the U-value, the better the insulation value of the material. Many build-ing and insulation products have their U-value indicated on their label. A U-value of 0.35 or less is recommended in cold cli-mates. In warm climates a low U-value is helpful during hot days or whenever heating is needed, but it is less important than SHGC (Solar Heat Gain Coefficient).

Q: What is R-Value?

A: R-value measures insulating power. The higher the R-value, the better the insulating power. To find the R-value you need to, check with your local power company. The R-value is the inverse of the U-value. Remember: If you install more insulation than necessary, you’ll waste money. When having insulation installed by a contractor, be sure to discuss what R-value is best for your home. Ask retailers and home installers for a fact sheet on insulation before buying. The fact sheet, required by the Feder-al Trade Commission (FTC), tells you the type of insulation, its R-value, and the area it will cover. When the contractor installs your insulation, they must give you a contract or receipt showing the insulation R-values, coverage area, and thickness. If loose-fill insulation is installed, the number of bags used must be included.

Q: What is Solar Heat Gain Coefficient (SHGC)?

A: The Solar Heat Gain Coefficient is the fraction of the incident solar radiation admitted through a window, both directly transmitted and absorbed and subsequently released inward. SHGC is expressed as a number between 0 and 1. The lower a windows solar heat gain coefficient, the less solar heat it transmits. A SHGC of 0.40 or less is recommended in warm climates. In heating-dominant climates, a high SHGC increases passive solar gain for the heating, but reduces cooling season performance, but reduces passive solar gain for heating.

Q: What is Visible Transmittance (VT)?

A: The visible transmittance (VT) is an optical property that indicates the amount of visible light transmitted through the glass. VT is expressed as a number between 0 and 1. The higher the VT, the more daylight is transmitted. A high VT is desirable to maximize daylight.

Q: What is Air Leakage (AL)?

A: The air leakage rate (AL) is a measure of how much air leaks through the crack between the window sash and frame. The rating reflects the leakage from the window exposed to a 25 mile-per-hour wind, and is measured in cubic feet per minute per linear foot of sash crack. Heat loss and gain occur by inflation through cracks in the window assembly. The lower the AL, the less air will pass through cracks in the window assembly. An air leakage rating (AL) of 0.30 cfm/sq ft or less is recommended.

Q: What is an NFRC rating?

A: The National Fenestration Rating Council (NFRC) is a non-profit collaborative of manufactures, builders, designers, govern-ment officials, utilities and consumers which provides unbiased energy performance ratings for window, door, skylight (or “fenestration”). NFRC’s labels provide product-specific performance ratings for technical qualities such as U-factor (the rate of heat loss from your home through the window), and Solar Heat Gain Coefficient (how much heat your house gains from the sun as a result of the window’s performance). Look for lower U-factor and appropriate SHGC numbers for highest efficiency performance in your area of the country.

Q: What is Energy Star?

A: Energy Star windows is a program designed to help consumers identify efficient windows, doors and skylights. By choosing Energy Star window products you can cut down your heating and cooling costs, and make your home more comfortable at the same time. Energy Star labeled windows are twice as efficient as the average window produced just ten years ago.

Q: Can I Trust My Measurements?

A: Yes, however we will not. Your windows will be re-measured by your installer at your pre-installation conference before your custom window order is placed with the manufacture.

Q: How Long before My New Windows are Installed?

A: Typically, your windows will be custom manufactured within three (3) weeks from the time we you order then. When they are ready, we will then coordinate an installation date that works with your schedule.

Q: How Long Does the Actual Window Installation Take?

A: Up to six (6) windows and one (1) patio door can usually be installed in one (1) day.

Q: Will I Lose Some of My Window Sill Space?

A: Sometimes. Some windows in home today have narrower frames whan replacement windows. Builders often use new con-struction (low grade) windows on new homes. Replacement windows are usually (1) to one and a half (1.5) inches thicker than the new construction windows.

Q: Can I Have New Construction Windows Installed In My Older Home?\

A: Yes, however, they are not recommended, and they cost only a few dollars less than a true replacement window.

Q: Do I Need Triple Pane Glass?

A: Not usually. These windows are designed for areas with prolonged extreme cold. With a third pane of glass the air space between the inside and outside pane is typically the same as two panes. The third pane adds 30% more weight to the sashes, placing an additional strain on moving parts. Three panes require two spacers which doubles the surface area that can fail. With new technologies in Low-E coatings, you can achieve better results against heat gain with two panes of 1/8 inch glass than you can with three panes. Glass is a conductor of heat. It does not insulate.Tucson Window & Door