Quick & Cheap Ways to Make Windows Energy Efficient

If you want to boost your home’s energy efficiency the windows are the best place to start. It’s not necessary to invest in replacement windows to boost performance. With some inexpensive materials and a day or two of work you can significantly cut your heating and cooling costs. Here’s how…

Assess the Situation

Although windows come in a variety of shapes and sizes, basic maintenance is the same for all types. Complicated upgrades or replacement may be necessary in some cases, but you can eliminate many common window problems on your own. Window inspection and repair is an easy do-it-yourself project that you can incorporate into your annual home maintenance routine.

Get started by doing an inspection of each window in your house. Carry a notepad, an old toothbrush or small paint brush, paper towels or sponge, a vacuum, WD-40, a small hammer and a multi-head screwdriver.

At each window, wipe away debris and vacuum out channels and cracks. Clean the hardware including sash locks and hinges. Lubricate any moving parts including cranks, sash locks, hinges and channels so that the windows can open and shut properly.

Check that caulking and weather-stripping are applied properly and not inhibiting the operation of the window. Caulk should be removed if interfering with window function or if it’s dry and loose.

If weather-stripping is interfering with window movement, it may be possible to reposition it by tapping the finish nails that hold it in place. However, loose weather-stripping is an indication that the adhesive has failed and it’s time to replace it. Remove any dry, loose weather-stripping. After all faulty seals are removed wipe down the window with a wet paper towel or sponge.

Make a List of Improvements

With the windows shut and locked, detect drafts or leaks by wetting your hand and tracing the window frames and sashes. Check for faulty operation of locks and hinges. Note any loose or misaligned sashes, warped frames, condensation, broken glass, rot and deteriorated seals.

If your window inspection has revealed cracked glass, rotted window frames or damaged sashes it may be time to invest in replacements. You can replace parts individually like glass or sashes if the frame and support are in good condition.

There are plenty of professionals who specialize in window repair, especially for vintage homes. If the entire window is in poor condition it’s worth the money to replace it with a high-performance upgrade.

As you inspect your windows, write down your observations as well as the number, size and types of the windows in your home including the basement. This will help you purchase the right materials and the needed amount.

It may seem like a lot of work and supplies, but the time and money you spend on these small upgrades will be significantly less than replacement windows and can payback in energy savings within a season.

Take Care of Easy Repairs

Start your window repairs during your inspection by attending to faulty hardware. Tighten sash locks on double-hung windows and hinges on casement and awning windows. These can loosen over time and impact airtightness.

These small improvements will realign sashes and seals to help reduce air infiltration as well as improve your home’s security. They will also increase the life span of your existing windows by eliminating unnecessary wear and keeping moisture out.

Stop Air Infiltration (warm or cold climates)

Insulate around windows

Even if windows and hardware are functioning properly, leaks may still be present. These are most likely between sashes and frame, but can also be a result of insufficient insulation between the window frame and the rough wall.

You can easily remove interior window trim and fill any gaps in insulation between the window frame and the interior walls with non-expandable foam or expanding foam designed to seal around windows. You can use fiberglass insulation but by itself it won’t stop air flow and leaks.

Carefully pry the trim from around the window with a wide putty knife and expose the window frame. Set the trim aside to be put back in place after filling gaps inside the wall. Fill any spaces around the window frame and trim away excess foam after it’s dry.

It’s important that the foam product you choose is labeled for use around windows as some expansion products can affect window operation. Foams made of HFC or propane propellants are a better choice as they do not contain chlorine which is damaging to the ozone-layer.

Apply Caulk & Weather-stripping

With trim in place you can move on to filling gaps between the window trim, sashes and frame. Caulk and weather-stripping can be used to fill small gaps under a 1/4 inch. These may seem insignificant but sealing even 1/8 inch gaps can reduce your heating and cooling costs by about 15%.

One of the quickest and least expensive ways to seal up leaky windows is to fill cracks and seams with an appropriate caulk. Both the interior and exterior joints around windows can be sealed with caulk to decrease movement of air and moisture.

It’s important to seal inside first and then move to the exterior. Sealing leaks from the inside out helps avoid trapping moist air inside the walls which can eventually damage structural materials and insulation. You also want to be sure to choose a product that is specified for indoor not outdoor use as exterior caulking products can give off harmful fumes.

You can use an acrylic latex caulk around the edge of window trim to seal between the window and the interior wall. This can be painted to match the trim color or you can purchase caulk in a matching color. Use this same caulk at all mitred joints of the trim (diagonal lines at corners) and between the trim and the frame.

If you have operable windows, like double-hung, you can seal them during seasons when you depend on your HVAC system most. Seal moveable joints between sash and frame with a weather-stripping caulk.

Weather-stripping caulk is applied the same as regular caulk but is designed to be easily peeled off without damaging finishes. If you caulk between sash and window, the window needs to remain shut to maintain the seal. However, this application will significantly decrease air infiltration and the window can always be resealed if you’re tempted to open it on a warm winter day.

If you don’t want to seal your windows shut, you may be able to reduce leaks sufficiently by installing weather-stripping at all movable joints. Weather stripping is standard in newer windows, but may be absent or deteriorated in windows over 10 years old.

Weather-stripping fills gaps and prevents the passage of air and water but allows sashes to slide open and closed. Weather-stripping can be placed in the channels that guide the window sash and at any moveable joint including between sashes, between sash and sill and between sash and frame.

Weather-stripping comes in a wide variety of materials and sizes. The kind of weather-stripping you will need depends on the types of windows you have throughout your home. The list you made during your inspection is enough information to purchase with confidence and any experienced hardware store staff can help you make the right choices.

Increase Thermal Resistance (warm or cold climates)

Interior Storm Window Systems

Air infiltration is just one principal of window performance. Thermal resistance is another important quality, especially on north facing windows. Just like insulation inside the walls of your home, windows need to have strong insulating qualities.

Newer windows enable this with multi layers of glass filled with air or gases. Older windows are often made of one layer of glass which can transfer heat between inside and out. You can experience this principle by placing your hand on a single glazed window on a winter day. If the glass feels cold, you’re losing heat through conductive transfer.

The best way to boost the thermal resistance of your existing windows is to create additional layers or "glazing" and trap air which is an excellent insulator.

You can do this by using storm windows, either inside or fitted to the exterior. If you already have exterior storm windows, use them. If your windows aren’t fitted for storms you have several options to increase thermal resistance.

Heat-shrink film is the cheapest and quickest version of a storm window. It is applied inside over the window frame or trim with double sided tape. The film becomes taut by shrinking it with a heat gun or hair dryer. These kits are sold at most hardware stores with complete instructions on installing them yourself.

This solution seals windows completely and is a cheap, effective application. The down side is that the plastic is fairly fragile and can be torn by pets or children, posing a safety hazard.

That same quality makes heat-shrink film fairly safe as the plastic can be torn open in case an emergency egress is needed. It’s a good choice for a home without children but it’s conspicuous and may not be pleasing to some aesthetic tastes. The other points to keep in mind are that these are one time use and the tape can damage paint when removed.

A step up from the heat-shrink film is a plastic film storm attached with spline and channel. These kits employ the same principal as a “Ziploc” bag seal. A plastic channel can be permanently fixed to the window frame with hardware or double-sided tape.

A clear plastic film zips into the channel and stretches across the window. The plastic is more durable than the heat-shrink film and can be reused for several years. The down side to this system is that the rigid plastic is not clear.

The most durable and finished looking interior storm consists of clear rigid acrylic with snap-on or magnetic seals. Acrylic sheets are easy to attach and remove and blend with the appearance of the window. These systems are a good choice for condominiums, vintage homes or anywhere aesthetics is a concern.

Exterior Storm Window Systems

Adding exterior storms is the best way to boost window efficiency and cost less than full window replacement. They are a larger initial investment than interior glazing solutions but are more affordable than window replacements.

Exterior storm window systems have many advantages over interior systems in performance and durability. They are made of a wood or metal frame and fitted with glass or acrylic glazing. Some systems are permanent while others are seasonal and need to be removed and stored.

Seasonal storm windows are usually a fixed pane of glass in a wood frame held in place with hooks or clips. They don’t allow for ventilation and impede egress in case of emergency. For this reason, seasonal storm windows don’t meet building codes in many municipalities.

Permanent storms are usually made of vinyl or aluminum with glazing and screen sashes that slide, allowing egress and ventilation. They are more economical, operable and provide better seals against air infiltration than seasonal storm windows.

If you choose to use exterior storms, it is important that you properly seal and repair windows inside first. Installing exterior storms over faulty windows will trap moisture and cause the window sash and frame to deteriorate. When installed properly, storm windows will improve thermal resistance while protecting the main windows and increasing their lifespan.

Exterior storms are available through most home supply retail stores and there are glass companies that specialize in retrofitting windows. You can purchase the materials and install them yourself, purchase the materials and have a contractor install them or hire a contractor to coordinate ordering and installation.

If you choose to hire a contractor, compare a few different companies. Get written estimates that detail the type of storm window, the costs of materials and labor and outline a time frame for installation. You can also ask for references from other homeowners who have used the service. Any worthwhile company will be happy to show off their previous work.

Take Control of Solar Gain

Solar gain refers to heat from the suns rays. Take control of solar gain by allowing it in during cold months and keeping it out during the heat of summer.

In warm climates, solar gain through windows can charge air conditioning systems and increase cooling costs. The best way to alleviate heat gain from the sun is to install overhangs or awnings and close drapes during the day. These solutions are especially useful on southern exposures.

There are also reflective films with adhesive backing which can be applied directly to windows. This application is effective in reducing heat gain and also protects interior finishes from harmful UV rays.

If your home suffers from intense solar gain, a reflective film can lower cooling costs. Just be sure to check with the manufacturer of your windows to ensure that the application is suitable. Reflective films can increase thermal stress and may damage windows if used improperly.

You can also cut down heating and cooling costs from solar gain through strategic landscaping. In cold climates, plant deciduous trees on southern exposures to provide shade in summer and allow sunshine and daylight in during winter. In warm climates choose evergreens or vines that will provide shade all year long.

Don’t forget the basement!

Steel casements and more recent aluminum versions are a popular window choice in basements but are poor insulators. These windows should be inspected, repaired and insulated just like the windows throughout your home’s living space. Fix faulty hardware, caulk cracks and install proper weather-stripping.

Fill large spaces between basement windows and the foundation with non-expandable foam or expanding foam designed to seal around windows. You can apply extra glazing by installing an interior storm window system, just be sure that the type you choose allows for immediate ventilation in case of emergency.

Reap the Savings

Once you complete your do-it-yourself window upgrade, you will notice immediate changes in thermal comfort. As your heating and cooling seasons pass, you'll also notice a significant decrease in your energy bills. The implementation of these simple strategies can improve your home's energy-efficiency significantly as nearly a quarter of wasteful heat transfer occurs through faulty windows.

Use the links and resources below for helpful tips on materials, techniques and more energy-saving strategies.

*Note: The information in this article is general advice and not meant as a substitute for personal guidance from a home improvement contractor. Although the author is a licensed realtor, the advice given in this article does not constitute any client contract or agreement between the author and the user. The author is not responsible for any losses, damages or claims that may result from your decisions.