Home window glass can be one of the best or worst aspects of your home, depending on quality. Replacing older windows with energy-efficient Insulated Glass Units reduces heat gain in the summer and heat loss in the winter so you'll be more comfortable and save money on heating and cooling.

Replacing older windows with energy-efficient Insulated Glass Units can decrease your energy bills and increase your home’s value in a tough real estate market.

Insulated Glass Units, commonly called IG units, are windows made from two or more pieces of flat glass separated by a sealed air space. IG units can be used in the home or a business.

If your home already has IG units, but there is condensation or a “milky” appearance between the panes of glass, Glass Doctor^® can upgrade your existing windows with new energy-efficient glass replacements.

Insulated Glass Advantages

IG units help maintain a consistent temperature in the home. In the summer, IG units reduce heat gain and in the winter they reduce heat loss. As a result, your home’s air conditioning and heating system should run less, saving energy and money.

IG units generally cost three times more than single pane glass windows. However, that additional cost can be recovered over the course of a few short years through lower energy bills. Plus, most IG units qualify for federal income tax credits.

There are two other advantages to IG units in addition to the energy savings. IG units reduce the tendency of condensation to form on the room side of the glass, and they can help soundproof the home by reducing the level of noise from the outside.

How IG Units are Manufactured

An IG unit must have two pieces of glass and an insulating spacer. A spacer is a metal tube around the perimeter of the IG unit. The spacer separates the two pieces of glass. Spacers are usually 3/16 of an inch and larger. A spacer is filled with a special moisture absorbing material called a desiccant (like the little bags you find in a shoebox with brand new shoes).

The perimeter of the entire unit is sealed with a high grade sealant. As a result, IG units should never have condensation. Some IG units have argon or krypton gas to the airspace between the two windows to further insulate. If an IG unit develops condensation, Glass Doctor can replace the glass, saving you the cost of a totally new window frame and the repairs to install a complete window unit.

There are two types of IG units commonly manufactured: Single Seal Units and Dual Seal Units. The difference between the two is the presence of a single- or double-seal between the spacer and the glass.

Single-sealed units can use several types of sealants: hot melt butyl, polysulfide, silicone, or urethane.

Dual-sealed units can use PIB tape for the primary seal and hot melt butyl (one part silicone, or two-part polysulfide) for the secondary seal.

The two glass pieces in an IG unit do not need to be the same type of glass. Patterned glass can be used as one piece, but the pattern should face the outside. If one of the pieces is reflective or tinted glass, it must face the exterior.

Energy Efficiency

When selecting an IG unit that is appropriate for your home, look for either the U-value or the R-value of the IG unit, depending upon the manufacturer. These Energy Performance Ratings are required for an ENERGY STAR label, but if the window does not qualify for ENERGY STAR you will have to ask before purchase.

The U-value is a measure of the heat gain or loss through glass due to the difference between the indoor and outdoor temperatures. The lower the U-value, the less heat is transmitted through the glass.

The R-value measures the overall resistance to heat transfer. The R-Value is the reciprocal of the U-Value. The higher the R-Value, the less heat is transmitted through the glass. For example, a material with an R value of 19 is a much better insulator than one with an R value of 6.

When considering whether or not to repair or replace IG units, consult with your Glass Doctor professional, who can explain the options available and find the right solution for you.