Interior and exterior storm windows

Interior storm windows have some advantages over exterior storm windows. And they are cheaper.

Interior storm windows can be tightly sealed to the primary window (much more than exterior storm windows) which makes them more effective at reducing air leaks. And since they aren't exposed to the elements they also have a longer life-span.

Besides, interior storm windows are easier to install and to remove, demand lower, have easier maintenance and support more features.

Drafts and Insulation

Both exterior and interior storm windows can reduce drafts and provide insulation, comfort and energy savings. They may also reduce sound transmission and provide UV protection.

Condensation and Cares

Exterior storm windows can be a cause of condensation (trapped between the primary window and the storm window) and a source of damages in the window frame. To avoid it, prefer exterior storm windows with sweep holes at their bottom.

Exterior storm windows also require more maintenance and more cares and cleaning than interior units, due to their exposure to elements and more difficult access.

Interior vs. Exterior Storm Windows Ventilation

It's easier to get natural ventilation with interior storm windows.

There are easily removable interior storm windows models to allow natural ventilation during milder periods.

Even interior models with mounting brackets permanently fastened can have detachable glass panes or detachable acrylic panes to allow ventilation - something that is impossible or much more difficult to implement with exterior storm windows.