Insulate & Seal Windows: Cut Down Energy Bills Now

As the leaves begin to fall and temperatures drop, you may notice a chill seeping through your windows, reminding you that winter is just around the corner. For many of us, particularly those with older or builder-grade homes, drafts and cold spots are a common problem, making it hard to stay warm without cranking up the heat. The reality is that these homes often lack the essential insulation needed to keep us warm in winter and cool in summer.

If you're looking to curb your increasing energy bills, it's high time you addressed one of the biggest culprits—your windows. Insulating and sealing them is a simple yet powerful way to enhance your home's comfort and energy efficiency, saving you lots of money.

Before you begin, assess your windows. Are there noticeable drafts? Can you see any visible gaps or deteriorating sealant? Identifying these issues will help you decide which insulation method will have the most impact.

According to NB Power, heating can account for up to 60% of your energy bill. Insulating your home against drafts can reduce your energy bill by as much as 10%. Over the colder months, this can result in savings of several hundred dollars.

Tools & Materials to Get the Job Done

• Minimally Expanding Spray Foam Sealant: Fills gaps without warping window frames
• NO WARP Window & Door Foam Sealant
• Weatherproof Exterior Sealant, Interior Sealant & Caulking Gun
• DYNAFLEX ULTRA™ Advanced Exterior Window, Door, Siding & Trim Sealant or SILICONE ULTRA™ Premium Window, Door & Siding Silicone Sealant 
• Learn about different types of sealants here
• Utility Knife: Cuts away old/excess sealant, foam, and drywall
• Pry Bar: For gently removing the trim
• Nails & Hammer or Nail Gun: To reattach trim after insulation
• Wood Filler (optional): fills nail hole
• Gloves: Shields hands from direct contact with foam chemicals
• Safety Glasses: Protects eyes from potential splashes or foam particles
• Respirator or Facemask: Prevents inhalation of fumes during application
• Drop Cloth or Plastic Sheets: Protects surrounding surfaces from accidental overspray
• Ladder or Step Stool: Provides access to hard-to-reach areas during application

Spray Away the Drafts

The gap between the window casing and the wall is often uninsulated during construction. If your space is still under construction, it is the perfect time to add a spray foam sealant to block air, moisture, and pests and even provide fire protection. If your home is complete, this process will involve removing the trim around the windows to access that pesky gap.

Step-by-Step Guide to Seal Windows from the Inside

1. Remove Window Trim: Start by carefully scoring the paint or sealant where the trim meets the drywall with a utility knife. Then, use a pry bar to gently remove the trim without damaging the wall.
2. Create an Opening for Spray Foam: If there is no visible gap to fit the straw applicator of your spray foam, use the utility knife to carefully remove about 2.5cm (1 inch) of drywall. Perform this step carefully so you don't cut through anything behind the drywall.
3. Apply Specialized Spray Foam: Fill the gap in the window frame with a minimally expanding spray foam sealant to prevent warping. Allow the sealant to cure fully according to the directions, typically 4 hours.
4. Reattach Trim: Before reattaching the trim, scrape away any old sealant and remove all the nails. If necessary, sand the trim to create a smooth surface for painting and sealing. Use a utility knife to cut away any excess cured foam, ensuring the trim can lay flat. Then, use a hammer and nails or a nail gun to reattach the trim, making sure everything is aligned correctly. A level can help ensure a straight installation.
5. Seal for a Seamless Finish: Depending on the condition of your trim, you can use wood filler or a paintable sealant to fill in old nail holes and hide new ones. It's crucial to seal between the trim and the wall and between the trim and the window to create an airtight seal. You may need to repaint, and you can do this before or after reattaching the trim. If you're using a paintable sealant like DYNAFLEX ULTRA, you can apply the sealant before or after painting for a clean, gap-free finish.

Image from Natural Resources Canada

Keep the Outdoors, Well, Outside!

After addressing insulation inside, it's equally important to seal your windows from the outside to protect against drafts, moisture, and potential damage. Exterior sealing prevents air leaks and helps keep rainwater from seeping into your walls, which can lead to mould and structural issues. By properly sealing your windows from the outside, you'll protect your home from the elements all year round.

Step-by-Step Guide to Seal Windows from the Outside

1. Assess the Trim: Start by assessing the condition of the exterior trim. If you notice any rot or significant damage, it's best to replace the trim entirely. For minor damage, you can use a repair product like PLATINUM PATCH to restore it before moving forward.
2. Remove Old Sealant: Carefully scrape away any old or deteriorated sealant around the trim. A clean surface will help the new sealant adhere properly and provide a better seal.
3. Apply New Sealant: Once the trim is ready, apply a high-quality exterior sealant between the trim and the exterior wall and window, creating a barrier that prevents drafts and moisture from seeping through the gaps. Apply an even bead and smooth it out to achieve a clean, professional finish. Pay attention to the recommended application temperature range for your sealant, especially if working in colder weather. Some sealants can be applied to wet surfaces, which is especially helpful during bad weather conditions. Keep in mind that silicone-based sealants are not paintable, but they are available in a variety of colours to match most trim styles, ensuring a seamless look.

Image from Natural Resources Canada

Other Creative and Cost-Effective Insulation Solutions

If you're looking for additional ways to improve insulation in your home, consider these budget-friendly solutions:

• Window Insulation Film or Bubble Wrap: Applying window insulation film to the interior of windows can significantly reduce heat loss. Bubble wrap is also a practical option for windows in low-traffic areas, such as basements.
• Thermal Curtains: Installing thermal curtains is an excellent way to insulate your home while adding style. They can help trap warm air inside during the winter and prevent heat from entering during the summer.

Additional Tips for Year-Round Comfort & Efficiency

Check for Air Leaks Regularly

It's a good idea to inspect your windows and doors regularly for air leaks. Doing this once or twice a year, preferably before winter and summer, can help maintain comfort and reduce energy costs.

Consider Window Replacement for Better Insulation

If your windows are older or significantly damaged, consider replacing them with energy-efficient models. Modern windows offer better insulation and can save you money in the long run.

National Resources Canada is an incredible resource for energy efficiency tactics. We recommend exploring the Keep the Heat in Guide for more helpful tips. A number of grants and loans are available as part of the Canada Greener Home Initiative—check your eligibility here. 

Learn More