Your thermostat is set to the hottest temperature, the windows in your home are fully closed, and all the drapes in your house have been dropped to help conserve heat, yet you are covered in blankets and fuzzy socks as your house still feels chilly. If this seems familiar, then your windows are the likely culprit. 

It is common for many homeowners to blame the constant chill on their faulty HVAC system or poor basement insulation without considering the state of the windows. Even when all the cracks in your home are sealed, damaged windows can still let in cold air, bringing down your home’s temperature and raising your heating bills because your furnace is working overtime.

If you are wondering how to insulate your windows from cold or heat without replacing them completely, we have solutions to suit every window type, insulation problem, and budget. 

How to Insulate Old Windows Without Replacing Them?

Insulating old windows can be tricky, especially if you cannot detect the damages and cracks. Since different windows require specific insulating materials, the first step is understanding the extent of the damage, the material used, and the window’s gaps and cracks.

Proper window insulation requires covering up air leaks and drafts responsible for bringing up your heating cost with strong sealants. Materials like window insulation film and panels, cellular shades, thermal curtains, glazing, caulk, and seal tape are some of the most common sealants used to insulate windows. 

While replacing your old windows with new ones may like the most logical thing to do, insulating the old ones is far better and will benefit you in the long run. Contrary to what many building and remodeling industries promise, replacing your old windows will not save you buckets of money in energy costs or drastically drop your energy consumption. But weartherizing an old window can save you a few bucks off your energy bill, so we created this article to teach you how to weatherize old vintage windows for better energy efficiency.

How to Insulate Old Windows From Heat

There are a few guidelines, conditions, and best practices that you must adhere to before insulating your windows from heat. You also want to ensure you set a realistic budget plan to go along with, or else the whole project might be unsuccessful. Insulating can be window-specific; while some types of window insulating materials might be perfect for a window style, they might perform poorly for another. 

The good news is you can create a durable barrier between the outside world and the inside of your home. These methods range from using materials to filling gaps, which can either be simple to complicated or low-tech to high-tech.

For homeowners looking for how to insulate old drafty windows or how to insulate existing windows without replacing them, weather stripping, applying caulks, and using insulating curtains can efficiently conserve your home’s energy.

Step 1. Choose The Best Weather Stripping Material

Weather strips are made from different types of pliable materials like foam weather strips, high-density foam weather strips, self-stick weather strips, and nail-on weather strips. 

Self-stick weather strips are perfect for metallic or vinyl windows with no room for nailing. They are also good for windows that press on each other, as sliding windows can easily dislodge the adhesive on the strips. Nail-on strips are perfect for hinged or wooden windows, while compressed-felt weatherstrip is a good choice for homeowners with warped windows that won’t allow rigid stripping. 

As you insulate the interior of your window, use high-density foam weather strips to insulate outside the window for better energy conservation.

For even more options and DIY solutions for insulating your windows in summer, read our guide on Windows Insulation For Summer: Options, Installation Tips, and Costs

Step 2. Prepare The Window For Installation

Make sure the window to be insulated is free from dirt by scraping off any chipping or loose paint. Also, remove any preexisting or worn-out weather strips before installing another. For rotten window wood, replace the wood with high-quality ones before you install any weather stripping material.

Step 3. Measure The Window

Measure the channels between the sashes and the window jamb (the vertical part of the window that supports the window sides) and note them down. Do this by using the strip to measure along the window sash on both sides and mark them.

Step 4. Insert The Strip

Cut out the measurement length for adhesive weather strips and carefully glue them between the sashes and jambs. 

Nail-on weather strips can be installed by nailing the stops on the nailing flange. Ensure the nailing flange sits evenly with the window’s inner edge and nails in the strips. As you nail, be careful not to pound too hard or risk breaking the window glasses. 

For windows that open outward, nail the weather strips to the outer edge of the frame; then, you can nail them to the inner edge of the frame for windows that open inward. While weather stripping sliding doors, attach tubular gaskets to the tops and bottoms of sliding windows with two sliding sashes and place spring-bronze strips in both side channels.

Do this by nailing the tubular gaskets along the windows’ sides, top, and bottom while attaching a spring bronze strip to the side channel that holds the slider. Ensure you apply more than one weather strip and use at least two to three strips for a better effect.

Step 5. Add Window Pulley Seals And Self-Adhesive Caps 

Although the weather strips are efficient enough, using window pulley seals and self-adhesive caps to cover the pulley area help stop the draft. Window pulley seals fit snugly over pulley weight holds of older double-hung windows and prevent draft. Clean the area and dry them completely before sticking these materials in place.

Step 6. Prepare To Apply The Caulks To Your Window

You should apply caulks after weather stripping to reinforce the window. But before you do so, choose the correct caulk type, as there are majorly two kinds: latex and silicone.

Both caulk types have their benefits and disadvantages; latex can be easily applied and removed but does not last long. Silicone caulks last longer but requires high proficiency before they can be applied or removed. However, companies now make siliconized latex caulks that are durable and easy to apply.

Step 7. Choose When To Apply The Caulks

Now that you have chosen your desired caulk material, pick a relatively suitable day to apply the caulk, as the weather condition can affect installation significantly. Ensure you pick a dry and cool day where the temperature is below 90° F and above 40° F. A colder temperature makes the caulk application difficult, and a hotter temperature prevents the caulk from hardening. 

Step 8. Prep And Prime Your Window

Prepare your window for caulking by removing any old caulk with a putty knife or a razor blade. If it proves to be difficult, use a hot gun or hair dryer to heat the old caulk for easier removal. There are also several caulk removal solutions can be found in your local store that melts the old caulk on your window.

Clean the window after removing the old caulk by wiping the area with a wet sponge or rag to get rid of any leftover caulk. After, dry with a clean cloth and brush off any removed residue with a bristle brush. Although this step is optional, priming your windows before applying the caulk is advised as it allows the caulk to stick better to the window.

Step 9. Apply The Caulks

Applying the caulk can be very tricky as it requires a great deal of professionalism. Start by cutting the nozzle to the right side, although must caulk cartridges come with markings that show the bead or caulk size before application. It’s best to cut at a 45° angle as it is easier to reach harder places during caulking after placing the cartridge in the caulk gun and making your first line.

Hold the nozzle opening to the window and make a long bead of caulk. Keep on applying pressure on the trigger to spread the caulk evenly. As you caulk, you will notice the caulk begins to dry immediately. Smoothen the caulk line by gliding a flat spatula over it to make the caulk job neater and provide more adhesion.

Step 10. Let It Dry.

After caulking, it is essential to let it dry thoroughly after 24 hours. Ensure you don’t touch it, as you will likely leave fingerprints or dents.

How to Insulate Old Windows From Cold

Insulating your window dorm cold is pretty much the same process as above. The reason is that it basically prevents cold air exit during summer and warm air exit during winter, thereby ensuring the temperature inside is constant for a long time. 

In addition to the steps listed above, insulating drapes can greatly help if you are on a quest about how to winterize.

The best thermal curtains have thick cushioning between numerous layers of cloth to stop air from escaping through the window and into your house. These window coverings have an insulating effect and the added benefit of filtering light and dampening sound. Using insulating drapes is the cheapest way to insulate for winter.

Read our guide if you’re also having second thoughts on whether you should insulate your garage.


Justin's been in construction for over 20 years in both new build and renovation. With experience in both commercial and residential construction, he specializes in healthier and more energy-efficient homes.

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