NOTE: This method uses a square butt-joint frame and the “wrap” method for the film. Stapling the film onto the frame edge, or starting it with a bit of dble. sided tape is easy and quick. The glue is optional, and without it, the frames can wiggle into an out-of-square window better. Butt joint frames are also easier for the homeowner without power tools to make. The film cannot be replaced as easily as when there are 2 separate film pieces.
Interior window panel tools and materials
- tape measure
- hair dryer
- power drill with drill bit, countersink, and philips head attachments
- staple gun for attaching pull tabs
- paper stapler for attaching film
- hand saw or chop saw
- table saw (if ripping your own wood)
- two corner clamps (optional)
- strips of ¾” thick pine or other soft wood, free of black knots. Strips are usually 1 1/4” wide, but can be wider for larger windows.
- wood for cross-braces every 3 ft for 1 ¼” frames, or 4ft. for 1 ½” frames
- 2” wood screws – coarse thread
- 100 gauge graphics-grade shrink film (a thicker, more durable version of the heat-shrink film found in do-it-yourself window kits, though these will work)
- pull-tabs made from cloth strips or re-enforced tape
- 1/2″ thick x 3/4″ wide open-cell foam tape
- wood glue (optional)
- clear packing tape: heavy duty, approx. 2” wide
For each interior window panel, you will need:
Roughly enough plastic to cover the entire panel twice, including the edges
Enough clear packing tape to go around the outside of the frame once
Enough foam tape to go around the outside of the frame once
Two strips of wood almost as tall as the window, and two strips almost as wide as the window minus the thickness of both side pieces
Strips for cross-bracing if one dimension is longer than 36”.
Step 1: Measuring – Measure the interior width (from one side jamb to the other) and the interior height (from the top jamb to the sill) of the window frame. If you see any separation between the moldings and the jamb, especially in older homes, take several measurements (i.e. top, middle and bottom, or left, center, and right).
Clicl here to see a short video on how to measure your window.
Because a tape measure curves at the corners and throws the measurements off, use a card to help you get an exact measurement. Add the card’s measurement to the number on the tape measure where it intersects the card. If the window isn’t quite square, the 1/2″ foam tape around the window panel will make up for some of the discrepancies. If the measurements are within 1/8″ of each other, use the median measurement.
If you have several windows that are close but not exactly the same size (i.e. within 1/8″ of each other), use the median measurements there as well, so that you can cut and make frames of the same size rather than fussing with very slightly different individual sizes.
Once you’ve measured the window, calculate the size that the frame needs to be by subtracting 3/4″ from each dimension. This will allow for 3/8″ of room for the slightly compressed foam tape around each edge of the finished window panel.
e.g. For a window with interior measurements of 24″ x 36″, the finished window panel frame should be 23 1/4″ x 35 1/4″. Note that some people have made panel frames only 5/8” smaller than the window opening (23 3/8″ x 35 3/8″). This gives a more snug fit, and is better for smaller straight-framed windows.
Step 2: Making the frame – Before you start to cut the frame pieces, you will need to buy or cut wood strips that are about 1 1/4″ wide and 3/4″ thick. You can rip one or more 1×6 pine boards into the right sized strips, using a table saw. 1×6 boards are actually 3/4″ x 5 1/2″, so if you cut each board into four long strips, you will end up with four 1 1/4″ wide strips. Wider wood strips are OK for larger windows, but use longer screws. If you need to cut your own strips, use a table saw with a finish carbide blade.
Cutting the frame strips – Avoid using any large twists, knots, or curves in the wood. You should try to get the straightest pieces possible.
Using a hand saw or chop saw, cut two frame strips so the longer dimension equals the frame measurements taken in Step 1. Make two frame strips for the longer dimension, and two (or 3) frame strips for the shorter dimensions less 2X the width of the wood. Cross-bracing (if needed) can be made from slightly thinner strips.
Sand the frame strips – You can use a sander or do it by hand. If you ripped the 1 1/4″ wide frame strips from a wider pine board, be sure to sand the rough sawn edges smooth.
Assembling the frame – Lay out the frame pieces. If possible, put the rough-cut edges facing into the winsert so that the outside will be smoother and the tape will adhere more easily.
If your window has a cross piece running across the middle of the frame, line up the cross piece of the winsert so that it it’s in the same position. Measure the position of the window cross piece and then mark the corresponding position on the side pieces of the winsert frame.
Using a 5/32″ drill bit, drill four to six “clearance” holes for the screws, two at the top, two at the bottom of each side piece, and two in the middle (if you have a cross brace). You can make a small plastic template the depth of the frame pieces (3/4″) with a hole to mark where the screws will go. Use this to make an indent in the wood before drilling screw holes. Use corner clamps to hold the corners together squarely and firmly. Go nice and straight and level.
It’s a good idea to use a countersink so that it will be easier to make the screw heads flush with the frame.
Screw the frame together. You may want to use a bit of wood glue to hold the pieces together while you position them. Screw the top, middle, and bottom pieces to one side first, then put glue on the ends of those pieces and screw them to the remaining side. Use a hand screwdriver for the final tightening so that the screws are flush with the frame.
NOTE: There are also other ways of assembling the frame (you could use corner biscuits, brads, etc.).
Check the squareness of the frame by measuring the diagonals to make sure they are the same length; adjust as necessary.
Try the frame in the window before putting the film on – if your window is out of square you can put paper shims in the joints for a better fit.
Step 3: Stain or paint the frame (optional) – Stain or paint frame to desired finish color.
Step 4: Attaching the plastic film – The plastic film tends to pick up dust. Any dust on the inside faces of the plastic film will be impossible to remove without removing and replacing the film.
CLEAN THE WORK SURFACE AND FRAME MATERIALS.
Cut a sheet of plastic shrink film so that it can wrap completely around the frame and there is about 3″ excess on all 4 sides of the frame, then lay half of it over the frame and center it. If using a roll, leave it double-wide when getting it started, then you can wrap it around the frame after the first edge is secure.
Staple the film to one edge, or use a strip of double-sided sticky tape to get it started nice and square. Then wrap the film around the frame tightly and staple or stick again.
Trim the excess film on the first edge, then staple or stick and trim the film on the other edges, like wrapping a gift box of chocolates!
Wrap the frame edges all the way around in heavy duty clear packing tape, centering the tape on the edges and gently folding it down onto the film on each face of the frame.
To shrink the film, use the hair dryer set on “high” and keep the hot air moving, about 3″ from the plastic, any closer might burn a hole in the film. This should only take two or three minutes, depending on the size of the window panel. Continue until all the wrinkles are out of the plastic and it is quite taut across the frame.
Step 5: Add pull tabs – The two small pull tabs at the bottom of the window panel are designed to make it easier to remove the window panel from the window. Cut two tabs for each window panel, about 1″ x 2 1/2″ each. These can be made from cloth, old straps, or re-enforced tape. Staple them to the bottom edge of the frame. Pound the staples flush to the frame with a hammer. If using tape, wrap it ½” up the back side of the frame, across the edge, and stick it back on itself to form the tab.
Step 6: Attach foam tape – Apply the 3/4″ foam tape all the way around the outside edge of the window frame. This will compress slightly when the panel is installed and will make a good fit within the window frame.
Use your fingers as a guide to align the tape with the frame. Pull the backing strip clear as you apply the tape. Do NOT stretch the foam when applying it. When you get to a corner, you can cut it and start it again on the next edge, overlapping it to make a nice square corner.
Step 7: Window panel installation and care – Install the window panel by pushing the top edge up to the top of the window frame, then pushing the bottom in gently. If you have difficultly pushing the panel into the opening, trying slipping a sheet of wax paper between the window opening and the window panel before pushing the panel in. Once the panel is in window opening, slip out the wax paper. Or you can use a bit of silicone spray on the foam.
If moisture builds up on the glass or window frame when the window panel is installed, remove the panel and wipe the moisture away so that mold does not form. To prevent moisture in the future, you can smear a thin layer of clear caulk on one surface of the foam, let it dry overnight, and re-install the panel. This will create a moisture barrier on the foam.
You can leave your winserts in all year round and they will also be effective at keeping the summer heat out. To store winserts, stack them carefully and protect them behind a solid surface if possible, to reduce the risk of the plastic being punctured. With careful handling, window panels will last for many winters. Small tears in the plastic can be repaired with clear tape. After several years you many need to replace the film and/or weather stripping.
You are now the proud owner of a well-crafted window insert, or “winsert”, which you can use year after year.
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