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BROSCO Insulating Window Unit MEASURING INSTRUCTIONS FOR ALUMINUM THERMALSCREEN

Green Mountain Window & Door Co.

IMPORTANT: These instructions apply to the most common installation method—mounting the ThermalScreen between the existing exterior window casing. Alternative approaches, such as surface-mounting onto the face of the casing, are possible but not addressed here. For best results, we recommend using a laser measuring device rather than a tape measure to ensure greater accuracy.

3. Determine ThermalScreen Height: To determine dimension “B,” begin by measuring from the point where the exterior face of the ThermalScreen will meet the window sill, straight up to the top horizontal casing (head casing). Because the ThermalScreen is 3/4" thick, take this measurement 3/4" out from the innermost edge of the exterior casing. Measure at both sides and in the center of the frame to check for straightness, and use the shortest of these three measurements. From that shortest value, deduct 3/16" to allow clearance for the weatherstrip—this result is your dimension “B.” You may adjust this gap slightly to suit your specific conditions, but be sure to leave enough space for the weatherstrip to function properly. If your window frame is out of square, measure diagonally from corner to corner inside the casing. If the diagonal measurements differ by more than 1/8", make an additional deduction to dimension “B,” typically equal to half the amount of the discrepancy. For example, if the diagonals differ by 1/4", subtract an additional 1/8". You can confirm the fit by following the “ProTip” below. 4. Determine Location of Mid-Rail: Measure from the inside edge of the top casing to the top of the meeting rail of your window. Record this as dimension “C”. The top of the ThermalScreen mid rail will be located at dimension “C”. P ro T ip : If you're unsure about your measurements, create a test template using cardboard or thin plywood cut to your intended dimensions. Ensure the corners are square and the edges are straight for an accurate fit. Position the template on your window where the exterior face of the ThermalScreen will be mounted— this should be 3/4” from the innermost edge of your exterior casing. Adjust the template until you can see a consistent gap: 1/8” along the top and sides, and 1/16” at the sill. These gaps are intentional and will be sealed by the ThermalScreen’s integrated weatherstripping. If the gaps you see are much larger or smaller remeasure.

1. Check Thickness of Existing Window Casing: We do not need this dimension for manufacturing purposes. However, your new ThermalScreen will be 3/4" thick. If your casing is less than 3/4" thick, contact your representative for options. If your casing is only 3/4" thick, you need to order without plunger pins and use our casing mounted thumb tabs for installation. If your casing is thicker than 3/4", use our standard plunger pin hardware for installation. 2. Determine ThermalScreen Width: Place measuring device on the sill and measure from the inside of the left casing across to the right. The same measurement must also be taken in the middle and the top of the window frame to verify that the frame is straight. Deduct 1/4" from the smallest of the three measurements and record the result as dimension "A". This will be the actual dimension of your new ThermalScreen. There will be a 1/8" gap between your ThermalScreen frame and your window casing. If you want this gap to be smaller or larger to adjust for your specific conditions feel free to change it, just keep in mind some gap is necessary for the weatherstrip.

Green Mountain Window reserves the right to make changes in product, specifications and instructions at any tine without notice. Not responsible for typographical errors.

NOVEMBER 2025

BI-13