Intelligent Energy Group’s window inserts create the most affordable and efficient thermal window insulation system today.  IEG’s window inserts will improve the comfort level of any office or building, reduce its energy consumption, and save you money.

The Department of Energy has determined that windows account for 30-54 percent of the energy loss in buildings and is the weakest link in the building envelope. The energy loss through windows has been estimated to be over $30 billion dollars annually in the United States alone.

Intelligent Energy Group is committed to providing the highest level of quality products and care for our customers. Our goal for you is to save energy, save money and improve comfort where you work.


IEG’s Window Insert is a clear, double paned polycarbonate window insert with an air tight gasket that fits snugly into the interior of an existing window opening.

It effectively creates two insulating air spaces that drastically reduce heat loss, while increasing comfort levels by keeping conditioned air separated from existing windows. It essentially makes a single pane window a triple pane.

It insulates the opening by stopping the permeating temperatures that glass cannot. The window insert slows the infiltration of solar heat gain and blocks 99% of the ultra violet (UV) radiation. When applied to a single pane window, it can improve the U-Factor by as much as 120% and the SHGC by 10%. It stops 99% of the air infiltration (drafty windows). It also has sound remediation qualities and can reduce noise by as much as 7 to 10 decibels.

The window insert costs 50-70% less than a replacement window with the same insulation value. Because of its unique gasket system, installation is simple, quick and with none of the mess and inconvenience.

IEG’s Window Insert helps your HVAC system work less to maintain the desired temperatures within your building. It allows more efficient climate control by eliminating the hot and cold air from entering or escaping.

The unique gasket around the perimeter is made of EPDM rubber and is resistant to extreme heat and cold, steam, ozone and weather conditions. It has an 85% memory retention. Because it is open and breathable, it reduces condensation. The stock color of the gasket is white but can be matched to almost any color through the extrusion process.

The polycarbonate has optical clarity and comes in various thicknesses depending on orientation and size. Stock thicknesses are .060, .118 and .150 but a variety of thicknesses are available.

The applications of IEG’s Window Insert is not limited to single windows alone. It can be applied to large window facings such as store fronts, insulating the entire “window wall”.

IEG’s Window Insert is an affordable, convenient, “super efficient” way to insulate your windows. Installation is simple, quick and does not require demolition or construction. IEG’s Window Insert will improve the comfort level of any office or building, reduce its energy consumption and save money.


IEG Window Insulator




Heat Gain and Loss¹

The Department of Energy has determined that as much as 54% of the energy in a home or building is lost though
fenestration. Windows, doors and skylights can gain and lose heat in the following ways:

  • Direct conduction through the glass or glazing, frame, and/or door
  • The radiation of heat into a house (typically from the sun) and out of a house from room-temperature objects, such as people, furniture, and interior walls
  • Air leakage through and around them

These properties can be measured and rated according to the following energy performance characteristics:


The rate at which a window, door, or skylight conducts non-solar heat flow. It’s usually expressed in units of Btu/hr-ft2-ºF. For windows, skylights, and glass doors, a U-Factor may refer to just the glass or glazing alone. But National Fenestration Rating Council U-Factor ratings represent the entire window performance, including frame and spacer material. The lower the U-Factor, the more energy-efficient the window, door, or skylight.

Solar heat gain coefficient (SHGC)

A fraction of solar radiation admitted through a window, door, or skylight— transmitted directly and/or absorbed, and subsequently released as heat inside a home. The lower the SHGC, the less solar heat it transmits and the greater it’s shading ability. A product with a high SHGC rating is more effective at collecting solar heat gain during the winter. A product with a low SHGC rating is more effective at reducing cooling loads during the summer by blocking heat gained from the sun. Therefore, what SHGC you need for a window, door, or skylight should be determined by such factors as your climate, orientation, and external shading.

Air leakage

The rate of air infiltration around a window, door, or skylight in the presence of a specific pressure difference across it. It’s expressed in units of cubic feet per minute per square foot of frame area (cfm/ft2). A product with a low air leakage rating is tighter than one with a high air leakage rating.

Test Results

Test Results on U-Factor of Materials used in the construction of the IEG Window Insulator. Steve McLean (Industrial Engineer)2 used the NFRC certified software to determine the U-Factor of the glazing material used in the IEG Window Insulator. The software is Windows 5.2 v 5.217a3 and the International Glazing Database4. The initial testing produced the following results (without gasket):

  • The IEGWindow Insulator alone (with Arkema Plexiglas) – (3mm Acrylic / .500″ gap /3mmAcrylic) U -factor =0.47
  • Clear Single-Pane glasswith The IEGWindow Insulator – 3mmglass /.625″ gap /3mm Acrylic /.500″ gap /3mm Acrylic U-factor = 0.31
  • Clear Dual-Pane Glass with The IEGWindow Insulator – (3mm glass / .500″ gap / 3mm glass / .625″ gap / 3mm Acrylic / .500 gap / 3mm Acrylic) U-factor = 0.23
  • Low-e5 Dual-Pane Glass with The IEG Window Insulator – (3mm glass / .500″ gap / 3mm Low-e glass / .625″ gap / 3mm Acrylic / .500 gap / 3mm Acrylic) U-factor = 0.15

Typically the glass only U-factor is 0.03-0.05 less than the unit U-factor. Additionally, glass with low emissivity coating will reduce the U-factor.

1. (Department of Energy)
2. (Steve Mclean -Expert in National Fenestration Rating Council, U.S. Department of Energy and Lawrence Berkeley National Laboratories practices and simulation tools)
3. (Window 5.2a v 5.217a -supported by the Assistant Secretary for Renewable Energy, Office of Building Technology, Building Technologies Program of the US Department of Energy)
4. (International Glazing Database)
5. (Simulated with IGDB ID codes 2001, 2011 and 2600 materials. Tinted glass 103,104, 2019)


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