1. Measure width between casings.
2. Measure from sill to bottom of the top casing.
3. If top and bottom sash are different heights, this is an ORIEL window. You must measure from the top of the opening to the center of the meeting rail.
4. Determine if window casing is EASTERN (see 4A) or WESTERN (see 4B).
5. When ordering, give width first, then height. If oriel, give the measurement from step 3. Specify if the casing is Eastern or Western.
6. Alternatively, you may measure an existing storm window and order the window TIP-TO-TIP. You must indicate whether or not the height measurement includes the expander at the bottom of the window.
