Location: Green Fret Consulting > Services > Ordering Interior Storm Windows

Ordering Interior Storm Windows

Where the Interior Storm is placed

interior storm figure 1
Fig. 1: Storm next to window sash.
model credit: Topher Belknap

We produce interior storm windows in a number of configurations and with a number of options, so you need to decide what is best for you. If you are unsure of any aspects of what you need, please contact us for a consultation. Firstly, the windows can be placed in a few ways within the window frame. The recommended way is having the interior storm up against the sash of the window (see fig. 1), this leaves a space between the outer film of storm and the glass of the window of around ½" which is near optimal in terms of insulation value. The insulation value comes from the air between the pieces of glass and the films, not from the materials themselves, which have low insulation values.

interior storm figure 2
Fig. 2: Storm between trim.
model credit: Topher Belknap

If there is some obstruction, such as shades or the handles of casements (though these can often be removed for the time when the storm is installed), the interior storm can be places further out from the window sash but still within the jams (see fig. 2). This maintains most of the insulation value while avoiding those other items. The storm stays in place by the tightness of the weatherstrip.

interior storm figure 3
Fig. 3: Storm outside the trim.
model credit: Topher Belknap

If there is insufficient room within the window jams, the interior storm can be placed on the sill and kept tight against the window trim, by means of mechanical fasteners (see fig. 3). The interior storm should be kept within 1" of the trim (measured from the outside face)in order to compress the weatherstrip and ensure a good air seal. In other words, the weatherstrip should be compressed to half its thickness just as if it was between the jams.

Two Panes or Three Panes

interior storm figure 4
Fig. 4: Triple Pane Storm.
model credit: Topher Belknap

We make interior storm windows in two pane and three pane versions. The former is more common, and will suffice for the majority of applications. The latter is unique to us, and is useful when either 1) The window requires a storm with stronger connection to the jams (skylights, for example) 2) The heat loss through the window is particularly great (e.g. if the window is single pane), 3) For skylights, which are a more significant hole in the insulation, and benefit from the more robust weatherstripping, 4) Thermal efficiency is of supreme importance, as for a Passivhaus or zero-energy house. The triple pane window is thicker (about 1½ inches) so the space where it sits needs to be greater. A wall made with 2" x 6" stud wall is likely to be sufficiently wide to hold a triple pane interior storm. These windows also come with a 1" wide (½" thick), UV resistant weatherstrip to increase the insulation value there as well.

Measuring your windows

Once you have decided where you want you interior storms to sit, the windows will need to be measured carefully. The thermal benefit of the interior storms depends on the fit to the windows, to maintain air tightness. Measurements should be made to the nearest 1/16" of an inch. Each measurement should be done at two places (say the top and bottom of the window for width). Write down both measurements, for both width and height (in that order) for each window. If measurements of the same dimension differ by more than ¼", measure both diagonals as well, to ensure that the storm will fit. Also write down a label for the window, so that the interior storm windows can be reliably replace in the proper windows every year. We will add the label to the backside of the window. If you want interior storms on the outside of the window trim, as in fig. 3, measure the window as before, but include the amount you wish to have overlap on each of the edges. And be sure to tell us.

We can come to your house and do all the measuring for you, for a fee based on the distance between your house and us.

Note: Window with either dimension exceeding 44" (or 50" in the case of triple pane interior storms) will require a cross-brace to ensure stiffness. If the window exceeds that in both dimensions, multiple cross-braces will be needed. If there is a particular placement of the cross-brace that you want be sure to note that down.

The Materials

We can build interior storm out of any wood, but in the interest of economy, we generally use either select grade pine with very few knots, or bright white primed pine. We can also match your existing trim-work in either wood or paint at an additional cost.


We price on a basic time and materials basis. Most double pane windows will cost between $35 - $60 for primed wood, and $30 - $50 for select pine. For triple pane windows, and for more exact prices and options, contact us for a quote. We can measure your windows, and delivery the completed windows for a fee (based on miles we need to travel).