Donovan Mirror and Glass

Most insulated glass units (IGUs) consist of two panes of glass (lites) connected by a spacer that encloses a space between the glass. Triple glazed IGUs are also available and offer improved energy efficiency over double glazed IGUs. IGUs are susceptible to seal failures, which is when air penetrates the space between the lites and increases the moisture level within. When it gets cold outside the moisture within the space can fog the glass or condense into water droplets. When this occurs only the IGU needs replacing, not the entire window sash. However, some window sashes have been made in such a way that reglazing is not an option. We will need to see the window before knowing for certain whether or not it can be reglazed.

Window energy efficiencies are rated by U-factor, which measures the heat flow rate. U-factor is the reciprocal of R-value (the resistance to heat flow), so the lower the U-factor the more efficient the window. Another important window measurement is the Solar Heat Gain Coefficient (SHGC), which measures the amount of heat gained on the inside from sunlight (the greenhouse effect). SHGCs do not need to be considered for windows not directly facing the sun, and in northern climates such as ours they are not as important as U-factors in determining energy efficiency. U-factors and SHGCs for IGUs are affected by glass coatings, the gas between the lites, number of lites, and types of spacers.

A double glazed IGU with both lites as clear 1/4" glass, with a 1/2" air space and an aluminum spacer has a U-factor of about 0.47 (R-value 2.1), a SHGC of about 0.70, and visible light transmittance of 79%.

An IGU with three lites is more energy efficient mainly because of the additional air space. A triple glazed unit without special coatings or gases will have a U-factor of about 0.33 (R-value 3.0). However, triple glazed IGUs are more susceptible to seal failures. A triple glazed unit has two seals and only one needs to fail for the window to fog up. Triple-glazed units are also more expensive than double glazed units. For these reasons most people choose to order double glazed IGUs from us.

The space between the two lites is filled with a gas and hermetically sealed with a desiccant within the spacer. The gas can be air, but for a lower U-factor we offer argon as an option. Adding argon gas to a double glazed IGU with clear 1/4" lites and a 1/2" air space will have a U-factor about 0.45 (R-value 2.2).

Low-emissivity (Low "e") glass coatings can be applied to surfaces of the glass to significantly increase energy efficiency. We offer several Low "e" coating options, typically applied to the inside surface of the outer lite and used in combination with argon gas for best results.

Spacers connect both panes together and seal the unit. They affect both the U-factor and the susceptibility of a seal failure. We offer three types of spacers: conventional aluminum spacer, Intercept® spacer, and Super Spacer®.

This is the standard spacer. It can be used for windows of various shapes, not just rectangles and squares. It can also be used on extra large windows.

The Intercept® spacer is a U-shaped metallic spacer that flexes with the glass under changing temperature conditions. Conventional aluminum spacers do not flex with the glass, which forces the sealant to flex instead making it much more susceptible to seal failures. The Intercept® spacer also transmits less thermal energy between the lites. An IGU with a conventional aluminum spacer that under test conditions yielded a U-factor of 0.33 (R-value 3.0), yielded a U-factor of 0.30 (R-value 3.3) with an Intercept® spacer.

There is no up charge for this type of spacer over the conventional spacer. However, Intercept® spacers are only available on rectangular (and square) windows. Also, the perimeter of the IGU cannot exceed 300 inches and we offer it for residential use only.

The Super Spacer® is a non-metallic foam spacer that also flexes with the glass under changing temperature conditions. This spacer offers improved resistance to seal failures, though we do not currently have data to show how it compares against the Intercept® spacer. The Super Spacer® is the most energy efficient spacer, and for the same IGU with a conventional aluminum spacer that yielded a U-factor of 0.33 (R-value 3.0), the Super Spacer® yielded a U-factor of 0.28 (R-value 3.6).

This spacer increases the cost of the IGU by about 25% over the cost of using a conventional spacer. There are no shape or size restrictions.

IGUs can be tempered for safety or strength. This is a building code requirement for IGUs installed in doors, sidelites next to doors, or windows within two feet of a floor.

Internal grids can add a nice touch to windows and can be ordered in different patterns. The most popular style is a configuration of horizontal and vertical grids evenly spaced. The spaces between the grids are called openings, and the price is determined by the number of openings rather than the size of the window. The standard colors and grid styles are shown below. For accurate color representation we recommend a visit to our showroom to see the actual grid samples.

To receive an estimate give us a call (262-785-1234) and provide us with your approximate dimensions. Just measure the visible glass (daylight opening) and round up to the nearest inch. We will add an extra inch to the daylight opening for estimation purposes only. If the window is a shape other than a rectangle we'll need to know that as well. Finally, we will ask you if the window is to be Low "e" with argon gas, and if it is to be tempered. If Low "e" is requested we quote Sungate® 500, unless you are interested in another coating listed on this page.

If we are installing the window we won't be able to give you more than an approximate range for labor pricing. We need to see how the existing window is installed to know how much time it will take to remove the old one and install the new one.

After receiving the rough estimate we will need to schedule a date and time for a field measure. After the measure we will give you a call with a firm quote. At this point to proceed we will need a 50% deposit. The IGUs will be installed approximately 1-1/2 to 2 weeks later, but for locations at the edges of our service area (such as Racine) the lead time could be longer.