Last winter I finally got tired of watching my heating bill climb while cold air seeped through the windows. The old house we bought came with original single-pane windows—beautiful wooden frames, terrible insulation. Replacing them would cost more than my car. So I started experimenting with window covers instead.
What I learned surprised me. Some DIY solutions worked almost as well as expensive window replacements. Others were complete wastes of time. Here’s what actually keeps heat in and drafts out.
Why Windows Leak Heat
Before covering your windows, understanding why they’re cold helps you pick the right solution. Windows lose heat three ways: conduction through the glass, air leakage around frames, and radiation to the cold outside surface.
Single-pane glass is the worst conductor. Heat literally flows through the glass from warm inside to cold outside. Adding any air gap between the glass and your living space dramatically reduces this—air is a lousy conductor, which is why it works so well as insulation.
Air leakage happens around sashes, where frames meet walls, and through any gaps in old windows. You can feel these drafts on windy days. The solution here is sealing, not covering.
Radiation is why standing near a cold window feels cold even with no draft. Your body radiates heat toward the cold glass surface. Heavy coverings reduce this effect by putting warmer material between you and the glass.
Insulating Window Film
The cheapest fix that actually works is clear shrink film. You tape plastic sheets around the window frame, then use a hair dryer to shrink the plastic tight. This creates an air gap between the film and the glass—essentially adding a second pane.
Installation takes maybe 15 minutes per window once you’ve done a few. The film costs a few dollars per window at any hardware store. It’s almost invisible once installed, which matters if you’re not trying to make your home look like a greenhouse.
Downsides: you can’t open the windows once the film is up, so plan to install it on windows you won’t need to open until spring. The tape sometimes damages paint or finish when removed, depending on your trim material.
I measured the temperature difference on my worst window before and after—the glass surface on a 20-degree night went from painfully cold to merely cool. The film creates enough dead air space to break the thermal connection.
Cellular Shades
If you’re willing to spend real money, cellular shades (also called honeycomb shades) provide both insulation and light control. The honeycomb structure traps air in pockets, creating insulating layers. High-end versions have double or triple cells for better performance.
The best cellular shades fit inside the window frame with minimal gaps at the edges. Light gaps around the edges leak both light and heat, so proper measurement matters. Many companies offer custom sizing—worth the extra cost for unusual window dimensions.
We installed double-cell cordless shades on our bedroom windows. The room stays noticeably warmer with them down, and the light control helps with sleep schedules. At around $100-200 per window for decent quality, they’re not cheap, but they’ll last years and you won’t need to reinstall every winter like plastic film.
Thermal Curtains
Heavy drapes have insulated homes since before central heating existed. Modern thermal curtains add foam or batting backing to trap air and block drafts. The key is getting them wide enough to overlap the wall on each side and long enough to puddle on the floor or windowsill—gaps let cold air circulate.
I’ve had mixed results with curtains. They work well when closed properly, but we rarely close ours during the day because we want the light. That defeats the purpose during the coldest hours. If you work from home and can keep curtains drawn, or if the windows face north and don’t provide useful daylight anyway, thermal curtains make sense.
The thermal rating matters. Look for curtains specifically marketed as insulated or blackout—regular decorative drapes do almost nothing for heat retention regardless of how thick the fabric looks.
Interior Storm Windows
The serious solution is adding interior storm panels. These are essentially second windows that mount inside your existing frames, creating a real air gap of an inch or more. Some versions use acrylic or polycarbonate sheets; others use actual glass in aluminum frames.
Installation ranges from DIY-friendly magnetic mount systems to professional custom installations. The magnetic versions use metal tape around your frame and magnetic strips on the panels—they pop off and store flat when not needed. More permanent interior storms may require trim modifications to create mounting points.
Interior storms cost more than film but less than window replacement. Expect $50-150 per window for DIY magnetic systems, more for custom glass panels. The insulating value approaches that of true double-pane windows, which is why historic preservationists recommend them for antique homes where replacing original windows would be inappropriate.
Weatherstripping
Before you cover your windows, check the weatherstripping. The best window covers won’t help much if cold air is pouring in around the sashes. Foam tape weatherstripping costs a few dollars per roll and takes minutes to install. V-strip or tubular weatherstripping lasts longer but requires more careful fitting.
The caulk around your window frames matters too. Old caulk cracks and separates, creating gaps that leak continuously. Removing old caulk and applying fresh sealant is tedious work but it’s work that pays off every winter.
What Actually Made a Difference
In our house, the combination that worked best was fresh weatherstripping, shrink film on windows we don’t need to open, and cellular shades on the bedroom windows. Total investment was maybe $200 for the shades, $40 for film and weatherstripping. Our heating bill dropped noticeably—not dramatically, since the windows weren’t our only efficiency problem, but enough to feel like the effort was worthwhile.
The windows closest to where we spend time got priority. Making the living room comfortable mattered more than insulating the spare bedroom no one uses in winter. Focus your budget on the windows that affect your daily life.
Next year I’m probably building interior storm panels for the worst windows—the living room picture window especially. But the temporary solutions have bought us time to plan and budget for the bigger investment. That’s the beauty of window covers: they let you improve gradually instead of requiring one massive project or continuing to freeze.
