Are the windows in your home drafty or leaky? If you are considering updating your old, inefficient windows, one of the most important steps is to measure for your replacement units.

It is critical to have an accurate measurement of the rough opening to ensure that your new windows will fit into your existing framework. Knowing the measurements of your windows will also be helpful when you are requesting quotes, as the size of your units will have a bearing on the cost, though for the purposes of a quote the approximate window size will suffice.

A guide to measuring windows

WindowMeasure-BHouse settling can change the size of your window openings and the dimensions can vary because the frame is not always straight. In order to get the most accurate measurement, it is important to measure from three different areas, both horizontally and vertically.

MEASURE HORIZONTALLY — To determine the approximate width of your window, measure between the jambs at the top, middle, and bottom of the window. Record the smallest number. The smallest measurement is used because it is much easier to adjust a window to a bit of a larger opening, than to try to fit one into a space that is even slightly smaller.

MEASURE VERTICALLY — Measure from the top of the sill to the top of the head jamb. Take the measurements from the left, centre and right of the window. Again, record the smallest of the three measurements. This will be the height of your window.

MEASURE FOR SQUARE — Over the years, your house can shift and settle, causing your window openings to become “out-of-square”. To measure the “squareness” of your windows, measure the diagonals from the upper left corner to the lower right corner and do the same from the upper right corner to the lower left corner. Record both measurements. If the two numbers are approximately the same, the opening can be considered to be square. If they are quite different, then this may cause your new windows to be installed in an out-of-square position. This can result in poor performance of your windows.

This condition can be avoided by installing a slightly smaller window so it can be installed “square” into the opening and then properly sealed for air-tightness.

PLEASE NOTE: This article is meant to be a guide only. Your window will extend slightly beyond the jamb extensions, meaning that measurements taken inside the jambs will most likely be a bit smaller than the new heel sizes you will need. For accurate measurements of your actual rough openings and the window heel sizes you will need, talk to the person who will be installing the windows.

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