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6 Ways to Seal Basement Windows for Winter

Winter months are known for their chill. As a result, most homeowners put in more effort to insulate their homes during this season so that precious warm air isn’t lost to the outdoors and cold doesn’t infiltrate into the house. I’ve put together 6 affordable ways you can seal your basement windows during winter in order to improve the temperature in your basement and the overall temperature of your home. 

1. Install New Weatherstripping

If your basement windows feature damaged or missing weatherstripping, then you should consider installing new weatherstripping. This would not only prevent cold drafts but would also prevent insects and dust from entering your home through the gaps in your window.  

MOPMS Draft Stopper Sweep, Door Weatherproofing Stripping, Window Seal Strip Self-adhisive Soundproof Seal Strip Cuttable Window Weather Stripping, Length 6.56Ft - Grey

The first step in weatherstripping windows is to remove any old weatherstripping, clean the surface, and wait for it to dry. This way, the material firmly adheres to the surface.

There are a couple of different types of weatherstripping options available to you. Most cost between $5 and $30 dollars, so it is an effective and affordable option.

You’d have to apply weatherstripping in line with your window type. If your basement windows feature a double-hung design, then you’d have more angles to cover than if you’re dealing with a casement window.

Type of WeatherstrippingMaterialHow to Install Pros Cons
Foam tape (amazon link)EPDM rubber or closed-cell foam* Measure the top and bottom window sash.
* Cut the foam tape using a utility knife in line with the window’s measurement.
* Peel away the backing and press the foam into place.  
Note that the foam comes in various thickness levels. So, choose one suitable for your window.
* Inexpensive 
* Easy to install.
* Suitable for both casement and sliding windows. 
* Lasts only up to 5 years and could wear out within a year. 
* Isn’t suitable for windows that experience constant traffic. 
* Might not be aesthetically pleasing.
* Could lose its grip over time and start pulling out of the window frame. 
V strip/tension strip (amazon link)Vinyl, aluminum, plastic, or stainless steel * Measure the top of the outer sash and the bottom of the inner sash. 
* Cut the tension strip, adding an additional two inches to the measurement of the v-strip. 
* Peel the backing off the strip.
* Press down the adhesive side of the strip to the inside of the window sash.
*Don’t stick the extra inch to the inner sash; instead, attach it to the underside of the sash. 
* Secure with nails for added protection. 
* Durable
* Blends into the window so it would not interfere with the decor. 
* Could make window hard to open/close.
Felt weatherstrip (amazon link)Felt* Measure your window sash.
* Cut out the felt in line with your measurement.
* Staple or nail the material into place.
* Easy to install.
* Inexpensive
* Only lasts up to two years
* Isn’t suitable for windows prone to moisture and abrasion.
* Is not aesthetically pleasing. 
Tubular gasket (amazon link)Flexible rubber or vinyl* Measure the exterior edges of your window.
* Cut out enough gasket to cover the measured area.
* Position tightly, and nail or staple in place. 
* Ideal for large gaps. 
* Durable
* Cannot be painted over to blend with existing decor. 
Spring metal (amazon link)Bronze, aluminum, copper, and stainless steel* Measure the window sash.
* Cut the amount of spring metal needed for the top and bottom of the window.
* Place it so that the flat side faces the interior angle of the window while the spring side faces the exterior area. 
* Cut out any part that might affect the movement of the window.
* Nail the spring metal into place.
* Use a screwdriver to gently bend the metal for increased tightness where necessary. 
* Durable
* Can last for years. 
* Ideal for moisture and traffic-prone windows.
* Difficult to install.

Note that all the weatherstripping options above have differing features. Thus, you’d have to examine your window and then select a solution that works best for you.

Weatherstripping windows can save energy costs by up to 10%.

2. Shrink Film

Shrink films are one of the easiest and most cost-effective ways to weatherize your basement windows. The process involves covering the window with a plastic sheet so that it prevents cold air from entering the room. The film essentially acts as a weather barrier so that air doesn’t pass through the window. 

Frost King V76H Shrink Window Kit 84-Inch by 110-Inch, Clear

However, it should be noted that this is only a short-term solution and should be removed after winter is over so that you can open your windows during warmer months.

You can either apply the film on the interior or on the exterior side of a window. But most homeowners prefer installing the film indoors. 

You would need:

How to install shrink film:

  1. Clean the window with a wet towel to remove dirt and dust.
  2. Leave to dry.
  3. Measure the window, adding an extra 2″ to give room for shrinkage.
  4. Cut the film to match.
  5. Apply double-sided tape (would be in the insulation kit) around the edge of the window frame, pressing it firmly to help it stick.
  6. Remove the tape liner.
  7. Starting from the top of the window, install the film and press it firmly to the tape.
  8. The hairdryer will be used to shrink the film and remove wrinkles (careful not to let the dryer touch the film).
  9. Cut excesses around the edges with scissors. 

Depending on what type of shrink wrap you use, the state of your window, and the weather condition in your region, a shrink film can reduce energy consumption up to 15%. 

Shrink films cost between $10-$20. Window insulation kits cost more, usually between, $15-$30, and contain fewer plastic films. But it contains enough films to seal multiple windows.

Alternatively, you can insulate your windows with bubble wrap (amazon link).

How to install bubble wrap:

  1. Clean the window.
  2. Measure your window glass.
  3. Cut bubble wrap to fit. 
  4. Using a spray bottle, lightly spray the window glass and the bubbly side of the wrap with water.
  5. Install the bubbly side of the wrap to face the window and the smooth side to face the room. 

A downside of using bubble wrap is that it isn’t as imperceptible as a shrink film. 

3. Tape the Windows Shut

If you’re not worried about aesthetics and need a seasonal seal for your basements windows, you can opt for this solution. It involves completely covering the window with plastic or silicon adhesive tape (amazon link)

Frost King Indoor & Outdoor B2 Mortite Caulking Cord 19-Ounce 90-Foot Long, Grey

This method involves placing adhesive tape directly on the glass. As a result, when it’s removed, the tape would most likely leave sticky adhesive residue, which might be difficult to get rid of. More so if the tape is left on the window for a prolonged period.  

How to tape windows:

  1. Lock the window.
  2. Clean the glass to remove dirt.
  3. Install the tape on the windowpane, avoiding folds or wrinkles.
  4. Tape the sash and edges of the window frame as well. 
  5. Press down to ensure that the tape properly adheres to the window. 

If you are unable to find a product designed for windows, you can use adhesive door seal tape to insulate your windows. The tape is inexpensive and costs as low as $7; however, depending on the quality of the product, the tape could cost up to $15. 

A major downside of taping windows is that you automatically render the window non-functional because the procedure implies that the window will be sealed shut until you decide to take off the tape. 

If you desire to see through your window, then you’d have to get a transparent tape. 

XFasten Transparent Window Weather Sealing Tape, 2-Inch x 30 Yards, Clear Window Draft Isolation Sealing Film Tape, No Residue

4. Cover with XPS Foam Board

Rigid foam is usually applied on exterior walls to insulate and improve the thermal properties of a house.   

There are a variety of rigid foam board options that you can use to seal your basement window. However, Extruded Polystyrene (XPS) is the most ideal option for below-grade insulation due to its high moisture resistance. Installing it over your window not only prevents air leaks, but it would also protect your window from the moisture that is so frequently an issue in basements

Although you can install the XPS board inside, it’s best to install the protective layer on the exterior side of the window. This way you protect your window from frost damage, especially in regions that experience heavy snowstorms. 

Note that if you decide to use fiberglass instead of a rigid foam board, you can only install the insulation inside the house. This is because although fiberglass functions as an effective thermal barrier, it is vulnerable to moisture. 

Thus, if you use fiberglass on your exterior window, especially during winter and moisture penetrates through its layers, the chilly liquid would settle on your closed window until you remove the board. This might not affect high-quality window panes, but if the glass is inferior, it could cause damage to the window. 

Blue XPS polystyrene insulation boards

You would need:

How to cover windows with XPS foam board:

  1. Clean the window to remove dust and dirt.
  2. Measure the length and width of the window.
  3. Cut the board to fit.
  4. Apply the adhesive to the window edges. Use a manufacturer-approved adhesive like this one (amazon link).
  5. Fit the board and press down to ensure that it adheres firmly to the window. 
  6. If your window has multiple panels, you might have to cut the board to fit each individual panel. 

This method wouldn’t be ideal if you do not want to completely shut off the window. This is because installing an XPS board implies that you shut out sunlight as well as the outside view. 

It would cost between $15-$30 if you already own a serrated knife/circular saw.  

Note that some states have laws against leaving foam boards exposed because they are flammable and create health and safety hazards. The boards are to be covered with drywall or paneling. 

5. Caulk the Windows

Caulk is a household favorite of DIYers. It’s ideal for closing gaps and cracks that are less than 1/4” wide. If there are gaps around your basement windows, you can close them with caulk. Or you could just apply caulk around the entire perimeters of your windows so that smaller openings that are not detectable wouldn’t expose your basement to the frigid air.

Man applying caulk between interior window and wall

Tips for using caulk in winter:

  • Regular caulks might not be suitable for the chilly weather so it’s best to use a silicone caulk.
  • If you’re applying the caulk on your exterior window, pick a time when it’s not snowing. 
  • Don’t apply caulk on wet surfaces. It could lose its adhesiveness if applied on damp surfaces. 
  • If you do not want the caulk to affect the facade of the window, you can opt for clear silicone caulk. 
  • For exterior applications, use an exterior grade caulk (amazon link)

You would need:

How to seal windows with caulk:

  1. Use a putty knife to detach old caulk.
  2. Brush off any debris and clean the surface with a towel dipped in soapy water. 
  3. Insert the caulk into the gun.
  4. Cut the nozzle to suit your desired bead size. Usually, 1/4” is ideal.
  5. Using a long wire, poke a hole in the caulk to release the sealant. 
  6. Apply the sealant around the perimeter of the window by consistently pressing the trigger. 
  7. For vertical applications, start from the top and progress toward the bottom of the frame. 
  8. Flatten the sealant with a plastic spoon (optional). 

For best results, apply caulk on both the interior and exterior window joints. 

For additional protection, you can temporarily seal off the window with removable caulk. The caulk would seal the windows and prevent air from entering your basement through the gap between the sill and the window frame. However, this procedure implies that you would be unable to open or shut the window until you remove the caulk. 

A major downside of insulating windows with caulk is that it does not account for air leaks due to faults in the window itself.  

You can double up your weather protection by applying caulk on your exterior window and installing a shrink film on the interior. 

Caulk Exterior Molding

The problem might be your exterior molding. If you notice gaps between your molding and wall or your molding and window frame, then you should apply caulk over them. 

If your exterior molding is old, it might feature cracks or holes. A temporary solution to this would be to apply caulk over the imperfections.

GE Sealants & Adhesives GE5000 Advanced Silicone 2 Window & Door Sealant, 10.1oz, Clear

For an air-tight seal, apply caulk around the four corners of the molding. It’s best to cover both the joints between the molding and the wall as well as those between the molding and the window. 

It costs between $10-$35 to caulk a window. The cost would be less if you already own a caulk gun. 

6. Hang Thermal Curtains

Also referred to as insulation curtains, thermal curtains (amazon link) prevent interior warmth from getting lost to the outdoor and restrict the penetration of chilly outdoor air.

They are usually made from moisture-resistant materials like polyester or microfiber. 

Thermal curtains comprise multiple layers of fabric. Usually, three layers, the first layer is solely decorative and faces the room, the second layer is composed of a thermally resistant material and the third layer acts as a protective backing that protects the inner layer from sun and moisture.   

Tips for installing thermal curtains:

  • Avoid single-layered drapes. Instead, go for curtains with double or triple layers.
  • Measure your window before purchasing the curtain. 
  • Purchase curtains with thick fabrics. Thermal curtains with flimsy materials do not provide as much insulation as those with thicker fabrics.
  • Open the window occasionally to prevent moisture build-up on the curtain’s vapor barrier.
  • The curtain can be cleaned while they’re installed with a vacuum and upholstery cleaner.  
  • Ensure that the curtain covers the window completely. 
  • Install the curtain close to the wall, so that there is no gap for air to escape through. 
  • Curtains should overlap in the center. There shouldn’t be a gap between them. 
  • Curtains should drop to the floor. 
  • Install a valance or cornice above the drape to limit air leaks. 
  • For improved insulation, secure the curtain to the frame with magnetic tape or hooks.

A major advantage thermal curtains hold over the other solutions I’ve discussed is that they perform multiple functions. They essentially limit the effect of outside weather on your home’s temperature. During summer, they prevent the heat of the sun from entering the house.

NICETOWN Thermal Insulated Grommet Blackout Curtains for Bedroom (2 Panels, W42 x L63 -Inch, Grey)

Alongside their thermal functions, they also dampen sound and filter out sunlight. Thus, the curtains are useful all year round, which more than makes up for their cost. 

However, if you have drafty windows, thermal curtains might not be enough to protect your basement from the winter chill.  If cost isn’t a problem, you can combine thermal curtains with any of the other sealing methods discussed in this article.  

The price of thermal curtains depends on factors like the quality of the materials used and the length of the curtain. But they are usually priced between $20-$45. 


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