Both types of storm windows – interior and exterior – help with home insulation and energy efficiency. They’re a layer added to your window to help regulate temperature, damp noise, and protect your existing window.
Interior and exterior windows have a lot of similarities. It’s in understanding their differences that will help you decide which is best for your home or building.
Exterior: Glass panels surrounded by wood or aluminum frame. These attach to the outside of your window frame using screws, caulk, or hinges. Sometimes the frame is semi-permanent so the pane will be released by swivel pins for cleaning or replacement while the frame stays attached to the house. Most have weep holes so accumulated moisture can evaporate.
Metal & Glass
Wood & Glass
Plastic & Glass
Interior: Interior storm windows are panels made of glass, vinyl, or acrylic surrounded by a frame of wood, metal, plastic, tape, or rubber. They attach to the inside of your window frame through magnets, adhesive, a track system, or compression system.
Silicone & Acrylic
Metal Foam & Acrylic
Plastic & Acrylic
Interior storm window benefits: Invisible from the outside, no weep holes for higher efficiency
Exterior: Exterior storm windows protect your windows and increase energy efficiency. Because of their weep holes, they cannot achieve a near airtight seal. This means they cannot stop all air and noise from getting in (where air goes, noise goes).
Interior: Interior storm windows can create a near airtight seal with very little air leaking through. Many are custom made to fit your window snugly (which means non-standard shapes a no problem), blocking air from entering or exiting. This helps with window soundproofing. The dead air space created between the window and insert adds to insulation and soundproofing.
Interior storm window benefits: Inside window insulation via dead air space, snug fit, custom shapes
Exterior: Exterior storm windows can interfere with curbside appeal as they are always visible and can obscure shutters, sashes, casing—all meant to provide 3D effect and add character. They can sometimes be painted to match home’s exterior. Exterior storm windows are used to preserve old windows, but detract from the home’s face by covering up details that make it interesting.
Interior: You cannot see most interior storm windows from the outside. Some you can notice from the inside, others disappear once they are in place. Is interior design important to you? Get interior window inserts that insulate your home while maintaining your aesthetic.
Interior storm window benefits: Doesn’t change home’s appearance
Exterior: Exterior storm windows can be medium to difficult to install. There’s no need for carpentry skills (unless you build them yourself), but there is need for a ladder unless your windows are basement or low to the ground. You will also need some hardware and tools. They have permanent to semi-permanent application. To maintain, you’ll need to climb that ladder again and use tools.
Interior: Interior storm windows can be installed without leaving your house. Some require semi-permanent hardware and tools to install. Some just push into place and can be removed and reinstalled easily.
Interior storm window benefits: Can be quickly installed and removed
There is a huge range when it comes to cost and quality for both exterior and interior storm windows. They are made of a variety of materials and can last a varying amount of time. One individual who is looking at custom wood exterior storms for his vintage windows said, “…the cost for these custom windows from a window shop, even just for five of them, yowza! We’re looking at prices into the thousands!” (via Old Town Homes) You can see another breakdown here.
Find the right kind of storm window for your situation, how much maintenance you want to put into it, and go from there. Good luck!