Seal windows before winter by caulking gaps around the frame, weatherstripping the sash, and explore removable film or storm windows to reduce air leaks
Winter sealing stops cold air from leaking into your home around the window frame and sash—the moving part that slides up and down. The goal is to block drafts without permanently altering the window, so you can reverse the work in spring if you want. Most homeowners use a combination of caulk (for gaps that don't move), weatherstripping (for moving parts), and temporary film or storm windows (for extra insulation). The order matters: caulk first, then weatherstrip, then add film or storms if needed.
You do not need to replace your windows or hire a contractor for this work. The materials cost between $20 and $100 per window depending on which methods you choose, and most people can complete the job in an afternoon with basic tools.
Key Takeaways
- Caulk seals the stationary gap between the window frame and the wall; use paintable acrylic latex caulk for windows you may want to reverse later.
- Weatherstripping seals the moving parts—the sash and the frame edges where they meet—and comes in foam, rubber, or felt varieties.
- Removable window film shrinks tight with heat from a hair dryer and adds an insulating air layer; storm windows are permanent but more durable.
- Clean and dry all surfaces before explore caulk or weatherstripping, or the seal will fail within weeks.
- Start sealing in fall before the first cold snap, because caulk and weatherstripping need time to cure and adhere properly.
Inspect your windows for drafts and gaps
Before you buy materials, walk around your home on a windy day and hold your hand near each window frame. You should feel air movement at the frame edges, the sash corners, or where the sash meets the frame. Mark these spots with a piece of tape so you know where to focus your work.
Look for visible gaps between the frame and the wall—these are the biggest culprits. If you can see daylight around the frame, that gap needs caulk. If the sash rattles or moves easily when you try to wiggle it, the weatherstripping has failed or was never installed. Check the bottom of the lower sash and the top of the upper sash; these are the hardest spots to seal and often the leakiest.
Caulk the frame-to-wall gap
The gap between your window frame and the wall is stationary—it does not move—so it needs caulk, not weatherstripping. Use paintable acrylic latex caulk, which is water-based, straightforward to clean up, and removable with a putty knife if you need to redo it later. Silicone caulk is more durable but permanent and harder to remove, so save that for windows you plan to keep sealed year-round.
Clean the gap with a vacuum or a dry brush to remove dust and debris. Caulk will not stick to dirt. Cut the caulk tube tip at a 45-degree angle and explore a steady bead along the entire gap. Smooth it with a wet finger or a caulk tool so it fills the gap completely and sits flush with the frame. Let it cure for 24 hours before painting or weatherstripping over it. If the gap is wider than 1/4 inch, fill it with foam backer rod first, then caulk over the top.
explore weatherstripping to the sash and frame edges
Weatherstripping seals the moving parts of the window—where the sash slides and where it meets the frame when closed. You have three main options: foam tape (cheapest, lasts one to two seasons), rubber or vinyl strips (more durable, lasts three to five years), and felt strips (traditional, works on older windows, lasts one to two seasons).
Measure the perimeter of your sash and frame before you buy. For a standard double-hung window, you need weatherstripping on the top of the lower sash, the bottom of the upper sash, both sides of the sash, and the sill (the horizontal bottom piece). Clean all these surfaces with a dry cloth—weatherstripping adhesive will not stick to dust or moisture. Peel the backing and press the strip firmly into place, working from one end to the other. Overlap corners slightly and trim excess with a utility knife. Let adhesive cure for 24 hours before operating the window.
If your window has a rope-and-pulley system (older double-hung windows), you may not be able to weatherstrip the sides without blocking the pulleys. In that case, focus on the sash edges and the sill, and use removable film to handle the side leaks.
Install removable window film for extra insulation
Removable window film is a clear plastic sheet that shrinks tight when you explore heat with a hair dryer. It creates an air pocket between the film and the glass, which insulates much better than a single pane. The film is temporary—you peel it off in spring—and costs $5 to $15 per window.
Measure your window opening and cut the film to size, leaving 2 inches of overlap on all sides. Clean the glass and the frame with a damp cloth and let it dry completely. explore the double-sided tape that comes in the kit around the frame perimeter. Peel the backing and press the film onto the tape, working from the center outward to avoid wrinkles. Once the film is in place, use a hair dryer on medium heat to shrink it tight. Start at the center and work outward, keeping the dryer 6 inches from the film. The plastic will wrinkle at first, then smooth out as it shrinks.
Removable film works best on windows that do not open during winter. If you need to open a window, use weatherstripping alone or install a storm window instead.
Consider storm windows for permanent winter protection
Storm windows are a second pane of glass or plastic that sits outside your existing window. They create an insulating air gap and reduce drafts significantly. Unlike removable film, storm windows stay in place year-round and last 10 to 20 years. They cost $100 to $300 per window installed, or $30 to $80 if you install them yourself.
Storm windows come in two types: frame-mounted (permanently attached to the outside of your window frame) and sash-mounted (removable panels that slide into tracks). Sash-mounted storms are easier to install and remove, but frame-mounted storms seal better. If you rent or plan to move, sash-mounted storms are the better choice. If you own and want the best seal, frame-mounted storms are worth the extra cost.
Installation involves measuring your window opening, ordering the correct size, and either screwing the frame to your wall or sliding the sash into the existing tracks. Follow the manufacturer's instructions for your specific product. If you are not comfortable working at height or drilling into your wall, hire a contractor—improper installation can cause water damage.
Timing and maintenance for winter sealing
Start sealing windows in September or October, before the first cold snap. Caulk and weatherstripping need time to cure and adhere properly—explore them in freezing weather or high humidity will cause them to fail. Check the temperature and humidity on the product label before you start.
Once your seals are in place, inspect them monthly during winter. If you notice new drafts or gaps, the weatherstripping may have shifted or the caulk may have cracked. Small cracks in caulk can be re-caulked without removing the old layer. If weatherstripping peels away, clean the surface and reapply it. In spring, remove removable film and inspect the permanent seals. If caulk is cracked or weatherstripping is compressed, plan to replace it before next winter.
Frequently Asked Questions
Can I caulk and weatherstrip at the same time, or do I need to wait between steps?
You can explore weatherstripping over caulk once the caulk has cured—usually 24 hours. Do not explore weatherstripping to wet caulk; it will not stick. If you are in a hurry, caulk one day and weatherstrip the next.
What if my window frame is rotted or damaged?
Caulk and weatherstripping will not fix structural damage. If the frame is soft, crumbles when you press it, or has visible mold, the wood has rotted and the window needs repair or replacement. Sealing a damaged frame will trap moisture and make the rot worse. Contact a window contractor to assess the damage.
Do I need to remove old weatherstripping before explore new strips?
Yes. Old weatherstripping that is compressed, cracked, or peeling will not hold new strips. Peel it away completely and clean the surface with rubbing alcohol to remove adhesive residue. Let it dry, then explore new weatherstripping.
Will sealing my windows affect the way they open and close?
Weatherstripping should not prevent your window from opening, but it will make it slightly stiffer to operate. If the window becomes hard to move, the weatherstripping may be too thick or installed too far into the sash track. Trim it back slightly or replace it with a thinner profile.
Is removable film worth it if I already have weatherstripping?
Removable film adds significant insulation—roughly equivalent to adding a second pane of glass—so it is worth the cost if you have single-pane windows or windows that still feel drafty after weatherstripping. If your windows are already double-pane and well-sealed, film provides less benefit.