How to Pick and Measure for Storm Windows.

It is important to have the proper measurements when ordering your storm windows, keeping in mind two important details.  Window type and clearance between the primary window and the storm window.  First, determine whether you need a blindstop window type or an overlap window type.  Storm windows installed to fit inside the existing trim over a sufficiently recessed primary window are called blindstop storm windows. 

If your primary windows do not recess into the house from the outside trim by a minimum of approximately 1 ½ inches we will recommend overlap windows.  This clearance is necessary in order to sufficiently operate your storm windows and screens from the inside of the home.  For reference, your blindstop trim is the last piece of trim as viewed from the outside, blocking in the actual window.  Most homes have layers of outer trim that step outward from the blindstop out to the brickmould, which is the outermost piece of trim. 

 

 

Blindstop storm windows are to be measured from the inside dimensions of the outermost trim inside (recessed from) the wall level outside your home at least 1 ½ inches away from your primary operating windows.  If you’re planning to install over a picture window, this required clearance can be reduced to ¾ inch as a minimum.  Blindstop windows are to be fastened to a recessed trim member with sufficient operating space between the storm window and the primary window.  Blindstop windows are flat in appearance as viewed from the outside.

Overlap storm windows are needed in places where there is not sufficient clearance between the storm and primary window inside the window frame and/or if there is not enough blindstop (less than ½ inch of exposed trim used to attach the storm window) to work with.  Overlap storms provide sufficient clearance and airspace between the storm and primary window and mount to the exterior surface of the window trim.  Overlap storm windows are raised in appearance as viewed from the outside.  

Remember – To order the correct size of storm window, your dimensions must read Width x Height.  Reversing the order will get you the wrong size window.

Measuring blindstop storm windows. 
Width:  Measure against the inner edge of the trim that will surround the frame of the window.  In short, measure the opening width atop the trim which the storm window will be fastened.  Measure each window opening horizontally in three locations at top, center and bottom.  Record the SHORTEST measurement. 

Height:  Measure against the inner edge of the trim that will surround the frame of the window.  In short, measure the opening height atop the trim which the storm window will be fastened.  Measure each window opening vertically in three locations at left, center and right.  Record the SHORTEST measurement. 

Check:  Measure diagonally from the pair of opposite corners from bottom left to top right and again from bottom right to top left.  If these numbers disagree then your opening is out of square and you should deduct 1/8 inch from your smallest width measurement and your smallest height measurement.  If the corner-to-corner dimensions are the same then use your original “shortest” width and height measurements as your ordering dimensions. 

** Note that these measurements are to be referred to as your “Opening Size for Blindstop Storm Windows”   The retailer or the factory should automatically deduct from these dimensions to order a storm window that comfortably fits inside the trim dimensions you specified allowing for a little maneuverability when installing them.

Measuring overlap storm windows:
Width:  Identify the outside trim that you will be fastening the window to.  Measure from the outer edge of the trim that surrounds the window from the outside.  In short, measure the width atop the trim which the storm window will be fastened.  Measure each window trim dimension horizontally in three locations at top, center and bottom.  Record the SHORTEST measurement. 

Height:  Identify the outside trim that you will be fastening the window to.  Measure from the outer edge of the trim that surrounds the window from the outside.  In short, measure the width atop the trim which the storm window will be fastened.  Measure each window trim dimension vertically in three locations at left, center and right.  Record the SHORTEST measurement. 

Check:  Measure diagonally from the pair of opposite corners from bottom left to top right and again from bottom right to top left.  If these numbers disagree then your opening is out of square and you should deduct 1/4 inch from your smallest width measurement and your smallest height measurement.  If the corner-to-corner dimensions are the same then use your original “shortest” width and height measurements as your ordering dimensions. 

** Note that these measurements are to be referred to as your “Frame Size for Overlap Storm Windows”   The retailer or the factory should order a storm window in those exact measurements or with only a small deduction.

Always install storm windows according to manufacturer specifications, which should be provided upon request from your retailer.  In any event, do not cover slits or other frame apertures with caulk or silicone because these small openings allow any moisture getting between the two windows to escape, and these also allow air pressure equalization and heat escape during hot months so there is not hot air trapped between the windows.