Insulating Your Windows: A Guide

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Home Improvement

In regions of the United States where winters are particularly harsh, poorly insulated windows can account for between 15 and 35 percent of heat loss. As the temperature drops, you might notice drafts entering your home from your windowsills. Even if you don’t feel cold air entering through gaps, single-pane windows offer little protection against the elements. In colder regions, this can result in significant increases in heating costs [source: Shurcliff]. In warmer regions, like the Sun Belt, windows can permit the sun to heat up your home, driving up air conditioning costs. Fortunately, there are ways to insulate your windows and protect your home from both of these issues.

There are many different methods for insulating windows, ranging from simple to complex, cheap to expensive, and low-tech to high-tech. Some homeowners opt for storm windows or double- or triple-glazed high-performance windows. Others prefer thermal shades or drapes of the right size and thickness. Some companies sell insulating panels and other products that can be installed on the indoor side of windows. If you’re on a tight budget, even bubble wrap can be an effective solution.

Preparing to Insulate Your Windows

Before you begin insulating your windows, it’s important to assess your needs. Start by identifying the areas of your home where heat loss is greatest. For example, if you have a north-facing kitchen with large picture windows, that might be a good place to start. Investigate whether drafts are coming from the sills or sashes, or if there is a lack of insulation at the window jambs or behind moldings. Consider your objectives for insulation. Are you looking for a year-round solution, or do you only need insulation during certain seasons? How much insulation do you need, and what tradeoffs are you willing to make? Will you sacrifice your view or the influx of natural light, or block access to your windows entirely?

When it comes to insulating your windows, cost is a factor to consider. You can opt for affordable solutions such as rubber or foam weather-stripping, or plastic sheeting. However, if you want more long-lasting solutions like insulation spraying or inserting, you may need to hire a contractor or a handy person. While these options may require more investment, they are worth it in the long run. Additionally, you can think about aesthetics, as tasteful window treatments or thermal shades can make a statement compared to caulk, foam, and vinyl. Once you have considered all these factors, it’s time to get to work by measuring the windowpanes, casings, and frames. If you plan to mount shades or blinds, you should decide whether insulating inside or outside the casing is better. Treating your windows with carefully mounted curtains, shades, and valences can help stop the flow of air around a window. However, window treatments installed with aesthetic considerations in mind may not provide optimal insulation.

To insulate your windows, you need to have some essential tools and techniques. One such technique is using plastic insulating film. You can find inexpensive window insulation kits that come with a sheet of plastic film and adhesive tape. Mount the tape around the window frame on all four sides, then mount the film and blow hot air at it with a hairdryer to tighten and make a firm seal. Another technique is using insulating drapes. The key is to ensure that there is no space left between the drapes and the window frame, windowsill, or floor by using weights, magnets, Velcro, snaps, or staples. You can also insert effective thermal shades while leaving existing drapes or shutters in place. Do-it-yourselfers can make them at a fraction of the retail cost. Insulating at window sashes involves prying off the molding surrounding the window frame, measuring a piece of rigid insulating foam to fit into the space between the window jamb and the wall, and spraying a substance like expanding polyurethane into the jamb itself.

In the end, your hard work will pay off.

Insulate Your Windows with Bubble Wrap

Using bubble wrap is a quick and budget-friendly way to insulate windows. Simply mist the interior of the window with water and stick the bubble wrap onto the glass with the bubbles facing the window. The bubble wrap can remain in place for months without any adhesive and can double the insulation value of a single-pane window [source: Build It Solar].

The Advantages of Window Insulation

Windows can be a costly feature in a home, as they account for significant heat loss in cold weather and heat gain in warm weather. Single-pane windows, which are found in nearly 50% of American homes, are the most energy-inefficient [source: Money Matters 101]. Improving the energy infrastructure of your home can help reduce heating and cooling costs and the use of fossil fuels, which can slow down the carbon emissions that affect the global climate.

Heat loss through windows occurs in four ways:

  • Air leaks in and out through gaps along the edges (infiltration).
  • Heat passes through the window glass (conduction).
  • Heat energy flows from a warm object to any cooler object nearby until equilibrium is achieved (radiation). This can cause up to 65% of the heat loss from your home.
  • Because heat rises and cool air sinks due to their different relative densities, the cold air at the interior surface of an icy windowpane flows toward the floor, pulling more air behind it to the window (convection). This movement eventually causes the overall room temperature to drop. This is why it’s essential to stop the flow of air around the window [source: Brighthub].

Effective window insulation reduces heat loss and helps regulate the interior glass’s surface temperature. Insulated windows prevent heat loss through leakage or convective airflow, ensuring an even temperature throughout the home, which improves energy efficiency. They also allow heated homes to maintain a higher humidity level, which results in better air quality and reduces the risk of condensation on the windows.

If you need further convincing that insulating your windows is worthwhile and saves energy and money, check out the links on the next page.

Measure Your Insulation with “R-Value”

The strength of insulation is measured using a unit called “R-value”: A higher R-value represents greater thermal resistance. For example, a single-glazed window has an R-value of about R-1 [source: Build It Solar]. Additional panes of glass can modestly increase that rating. One fiberglass window manufacturer claims insulation ratings of up to R-11 [source: Serious Windows].

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The following list provides links to various resources on how to insulate windows, including articles, videos, and DIY projects. These resources offer tips and instructions on how to improve energy efficiency and save money by insulating windows using materials such as bubble wrap, thermal shades, fiberglass, and more. Some of the sources include “This Old House” magazine and television, “Mother Earth News,” and “Money Matters 101.”


1. What is window insulation?

Window insulation is a process that involves adding layers of material to your windows to reduce heat transfer. This can help keep your home warm in the winter and cool in the summer, as well as reduce your energy bills.

2. What are the benefits of window insulation?

Window insulation can improve the energy efficiency of your home, making it more comfortable and reducing your energy bills. It can also reduce outside noise and improve the durability of your windows.

3. What types of window insulation are available?

There are several types of window insulation available, including weatherstripping, caulking, and window film. You can also install storm windows, which are designed to provide an additional layer of insulation.

4. Can I install window insulation myself?

Yes, many types of window insulation can be installed by homeowners. However, if you are not comfortable with DIY projects or have complex window configurations, it may be best to hire a professional.

5. What materials do I need to insulate my windows?

The materials you need will depend on the type of insulation you choose. Common materials include weatherstripping, caulk, window film, and insulation foam.

6. How do I know if my windows need insulation?

If you notice drafts around your windows, or if your energy bills are higher than usual, your windows may need insulation. You can also perform a simple test by holding a candle or lighter near your windows to see if the flame flickers.

7. Can window insulation damage my windows?

No, when installed properly, window insulation should not damage your windows. In fact, it can help improve their durability and lifespan.

8. How much does window insulation cost?

The cost of window insulation will depend on the type of insulation you choose and the size of your windows. DIY options can be relatively inexpensive, while professional installation can cost several hundred dollars.

9. How long does window insulation last?

The lifespan of window insulation will depend on the type of insulation and the conditions in your home. Some types of insulation can last for several years, while others may need to be replaced more frequently.

10. Can window insulation improve the value of my home?

Yes, improving the energy efficiency of your home can increase its value. Window insulation can also make your home more attractive to potential buyers.

11. How can I choose the best type of window insulation for my home?

The best type of window insulation for your home will depend on your budget, the size of your windows, and your insulation needs. It may be helpful to consult with a professional to determine the best option for your specific situation.

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