Intelligent Energy Group’s thermal optical window inserts create the most affordable and efficient thermal window insulation system today.  IEG’s thermal optical 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.


Patent #11,933,102


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 25%. 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 inserts costs 50-70% less than a replacement window with the same insulation value and installation is simple, quick and with none of the mess and inconvenience of replacement windows.
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 range from .118mm to .150mm but a variety of thicknesses are available.
The applications of IEG’s Window Inserts are not limited to single windows. They can be applied over large window spans such as store fronts, insulating the entire “window wall” where the mullions and sills of varying materials can often permeate the same as the glass they surround.
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


Temperature data logger study results from two adjacent offices, one with window inserts and one without in a NYC high-rise over a two-week period in June of 2021.

IEG Window Insulator
IEG Window Insulator

Informal temperature reading difference of 21 degrees between the window temperature in our office Suite 408 with IEG Inserts installed and Suite 415 directly next door without.

IEG Window Insulator
IEG Window Insulator
IEG Window Insulator
IEG Window Insulator
IEG Window Insulator

IEG Thermal Optical Window Insert*
Independent Testing Summary

Analysis conducted by the U.S. Department of Energy has shown that window attachments have the potential to save significant energy. The Window Coverings Manufacturers Association (WCMA) was awarded D0E funding to help capture these potential energy savings through the creation of a comprehensive rating, labeling, and certification program for window attachments, which is administered by the Attachments Energy Rating Council (AERC).
Intertek is an AERC accepted calculation entity and all simulation was performed using AERC thermal modeling software developed by Lawrence Berkeley National Laboratory (LBNL) for rating the Energy Performance of fenestration attachments.
Intertek, an IAS Accredited Testing Laboratory was contracted to perform independent testing for air leakage, U-Factor, solar refraction, and sound transmission through computer simulation and physical testing of lEG Thermal Optical Window Insert* across 3 variations of base windows.
Baseline – B: Wood frame with double glazed, clear glass (.456 U Factor) (.639 SHGC)
Baseline – D: Non-thermally broken aluminum, single glazed clear (1.118 U Factor) (.717 SHGC)
Baseline – E: Non-thermally broken aluminum, double glazed clear (.677 U Factor) (.670 SHGC)

(AL) Air Leakage is expressed in cubic feet of air passing through a square foot of window area. The lower the AL, the less air will pass through cracks in the assembly.
Air leakage testing is done by using a wood framed base window with a sheet of Lexan as the glazing, holes are drilled until the air leakage is equal to 2cfm/ft2. Once the base window has been calibrated, the IEG insert attachment is added and the air leakage is retested and repeated for all variations of AERC’s base windows.
The results from the air leakage report K9807.01-109-44 show the base windows AL of 2 was reduced to an AL of .01 (an improvement of 99.5%) ** with the IEG Insert.
U-Factor is the rate of non-solar heat loss or gain through a whole window assembly, measured in Btu/ hr-sf-F. The lower the U-Factor the greater a window’s resistance to heat flow and the better its insulating value. Intertek performed 3 simulations.
K9807.06-301-45 (show U-factor w/ Thermal Optical Insert as .23) – Baseline B
K9807.04-301-45 (show U-factor w/ Thermal Optical Insert as .41) – Baseline D
K9807.05-301-45 (show U-factor w/ Thermal Optical Insert as .34) – Baseline E
This represents a 49.56%, 63.33% & 49.78% improvement in U-Factor over baseline.

(SHGC) Solar Heat Gain Coefficient is the fraction of incident solar radiation admitted through a window. SHGC is expressed as a number between 0 and 1. The lower the window’s solar heat gain coefficient, the less solar heat it transmits, and it’s (SC) Shading Coefficient is 87% of the SHGC and represents the incident solar radiation reflected by shade or shadow.
K9807.06-301-45 (show SHGC w/ Thermal Optical Insert as .49) (SC Calculated at .426) – Baseline B
K9807.04-301-45 (show SHGC w/ Thermal Optical Insert as .53) (SC Calculated at .461) – Baseline D
K9807.05-301-45 (show SHGC w/ Thermal Optical Insert as .51) (SC Calculated at .444) – Baseline E
This represents a 23.32%, 26.08% and 23.88% improvement in SHGC over baseline.
(STC) Sound Transmission Class is a single number rating of the airborne sound transmission loss (TL) performance of a constructed assembly measured at standard one-third octave band frequencies. The higher specimen TL is above the base window STC rating, the more efficient the attachment will be at reducing sound transmission within the frequency range of the test, in this case frequencies to represent sound typical of modes of transportation and urban daytime construction.
Testing of the IEG Thermal Optical Window Inserts* show’s that the (OITC) Outdoor-Indoor Transmission Class rating increased from 22 with the baseline window to 26 with the baseline window & insert combined, an 18% sound reduction over baseline.