Best Window Insulation Kits and Draft Stoppers 2026
Air leaks are the cheapest heating problem to fix and the one most people ignore because it is not a product you look forward to buying. A house typically loses a quarter to a third of its heat through gaps rather than through walls.
The fixes below cost between $10 and $60 and pay back within one winter. The order matters: seal air leaks first, then add insulation film, then think about curtains.
What is in this guide
Quick verdict
- Biggest single win: shrink film window insulator kits
- Cheapest win: draft stoppers under exterior doors
- Most overlooked: foam gaskets behind outlets on exterior walls
Where the heat actually leaks
| Leak point | Typical share of air loss | Fix | Cost |
|---|---|---|---|
| Gaps around doors | Large | Weatherstrip and draft stopper | $15 to $30 |
| Window frames and sashes | Large | Shrink film kit, rope caulk | $20 to $40 |
| Outlets on exterior walls | Small but everywhere | Foam gaskets | $10 |
| Attic hatch | Often the single biggest | Weatherstrip and rigid foam | $25 |
| Fireplace damper | Large when open | Chimney balloon or closed damper | $40 |
The attic hatch is the leak nobody looks at and often the largest one in the house, because warm air rises and leaves through it continuously. Weatherstripping it takes twenty minutes.
What to buy
3M Indoor Window Insulator Kit
Biggest single win
- Type: Shrink film kit
- Coverage: Five windows per kit
- Install: Double-sided tape plus a hairdryer
Shrink film creates a still air gap in front of the window, which is what actually insulates. It is close to invisible once shrunk tight, and it stops the cold draught that falls off a single-glazed window and pools at floor level.
The install takes about ten minutes per window. The one rule is to clean and dry the frame first, because the tape will not hold on a dusty or damp surface.
Pros
- Noticeable difference in a single-glazed room
- Nearly invisible once installed
- Cheap per window
- Also cuts condensation on the glass
Cons
- Windows cannot be opened until spring
- Tape can pull paint on removal
Under-Door Draft Stopper
Cheapest win
- Type: Twin-sided door stopper
- Install: Slides under the door
A one inch gap under a standard door is equivalent to a hole in the wall roughly the size of a brick. A twin stopper seals both sides at once and moves with the door.
Ten dollars, no tools, works immediately. Start here.
Pros
- Instant effect, no tools
- Works on any door
- Also blocks noise and dust
Cons
- Slides out of place on thick carpet
Weatherstrip Seal Tape
Best for door frames
- Type: Adhesive foam or V-strip
- Use: Door and window frames
Weatherstrip tape seals the perimeter that a draft stopper cannot reach. V-strip lasts longer than plain foam and compresses less over time.
Clean the frame with alcohol first. Adhesive failure in cold weather is almost always a surface prep problem.
Pros
- Seals the whole door perimeter
- Cheap and easy to reapply yearly
Cons
- Adhesive fails if the surface is not clean
- Foam compresses within a season
Outlet and Switch Gasket Sealers
Most overlooked
- Type: Foam gaskets
- Use: Outlets and switches on exterior walls
Every outlet on an exterior wall is a hole through the insulation. Foam gaskets behind the cover plates take two minutes each and cost pennies.
Turn the power off at the breaker before removing cover plates.
Pros
- Extremely cheap
- Fixes a leak most people never consider
Cons
- Requires removing cover plates
- Small individual effect, adds up across a house
Thermal Blackout Curtains
Best comfort upgrade
- Type: Thermal lined
- Effect: Reduces radiant loss and draught
Curtains do not seal air but they do cut the radiant chill from a cold pane and slow the draught that falls from a window. Full length, close to the wall, and closed at dusk is what makes them effective.
Open them on sunny days for free solar gain, and close them the moment the sun is off the glass.
Pros
- Improves comfort immediately
- Also blocks light and noise
Cons
- Does not seal air leaks
- Only works if actually closed at dusk
Draft sealing FAQ
Does window film really work?
Yes, on single glazed or old double glazed windows. It creates a still air layer, which is what insulates. On modern triple glazing the benefit is minimal.
How do I find drafts?
Hold a lit incense stick or a thin tissue near frames, outlets and the attic hatch on a windy day. Movement shows the leak.
Will sealing my house cause damp?
It can if you seal a house with no ventilation and no extraction. Keep bathroom and kitchen extractors working and use a hygrometer to keep indoor humidity under 55 percent.
How much can draft sealing save?
Estimates vary by house, but 10 to 20 percent of heating cost is a common range for a leaky older home, for under $100 of materials.
Can I still open the windows with film installed?
No, that is the trade-off. Leave one window per floor unfilmed for ventilation.
What is the single best place to start?
The largest exterior door and the attic hatch. Both are large leaks and both are cheap to fix.
What to buy first
Final verdict
Start with a draft stopper on the main exterior door and weatherstrip on its frame, then film the windows in the rooms you use most. Total cost under $60 and the effect is noticeable within a day.
- Biggest win: 3M Indoor Window Insulator Kit
- Cheapest: Under-Door Draft Stopper
- Most overlooked: Outlet and Switch Gasket Sealers
Once the heat stays in, heating the person is cheaper than heating the house. See our heated mattress pad guide and the infrared heater guide.