Windows have a huge impact on how our homes look, feel and function, so we  want to get them right. But even the best windows have a hard time doing  everything we want them to do — let in light and views, keep out the cold, etc.  Happily, homeowners can make their windows perform better by choosing  energy-efficient window treatments such as insulated curtains and blinds.

You can find some great solutions for how to make windows more  energy-efficient — and your home more comfortable — without spending a lot of  money. You can even make some insulated window coverings yourself.

Out the Window

Windows are often described as “holes in the wall” for good reason. The U.S.  Department of Energy (DOE) reports that windows typically account for 25 percent  of annual heating and cooling costs in older houses, and can even be responsible  for as much as 40 percent.

Even those of us whose homes have high-performance windows want them to work  better. “It doesn’t matter whether you get the best window in the world. The  first thing that anybody is going to do is change the way it works,” says Peter  Yost, vice president for technical services at the publisher BuildingGreen.  These changes take place with the addition of blinds, insulated shades, thermal  curtains or other coverings.

So how do we make window treatments work for us, and still be efficient? To  get the most out of our windows, we need them to be adjustable. Depending on the  season and time of day, we may want to let in as much light, heat, fresh air and  view as possible — or do our best to keep those things out — in the name of  comfort, energy efficiency and privacy.

Check the Payback on New Windows

Replacement windows are easy to get excited about because they offer  efficiency features that can lower your energy bills. However, many  green-building professionals agree that replacement windows are usually not an  effective way to spend your money. Less expensive energy-efficient window  treatments — such as plastic sheeting and thermal curtains — are often better  bets. “If you have decent windows now, does it pay to replace them? No. They’re  not going to pay you back in energy savings,” says Ken Riead, a home-energy  rater and trainer with Hathmore Technologies in Independence, Mo.

The easiest way to find out whether you have efficient windows is to have a  home energy audit. For a few hundred dollars — a fraction of the price of  installing new windows, new wall insulation, or even a new heating and cooling  system — a home energy professional will come to your residence to evaluate  which options are a good deal by calculating the energy saved and the payback  period. Specifically regarding windows, a home energy audit will assess whether  your best investment would be new windows, storm windows, or additional  weatherstripping and caulking. (Get the full scoop at Home Energy Audits: Measure Your Energy Costs and Add Up the  Savings.)

Regardless of whether you end up replacing your existing windows, you should  look into ways of improving their performance. With the exception of storm  windows, recommendations about energy-efficient window treatments (cellular  shades, thermal panels, awnings, etc.) are probably beyond the scope of a home  energy audit, so you’ll need to do some further research. Luckily, much of the  legwork has been done for you.

A good starting place is the “Weighing Your Window Options” chart (See also in Image  Gallery). As you can see, no single energy-efficient window treatment will work  for everyone. You may think the hands-down best choice is insulated cellular  shades — because the chart shows they have one of the highest possible  insulation values — but cellular shades have poor resistance to condensation,  which can be a serious issue in cold, wet climates. Indeed, any window covers  that allow warm, moist interior air to come into contact with cold glass will  cause water droplets to form — risking rot and mold on wooden window frames.  Homeowners can stop condensation from forming by creating a vapor barrier that  prevents moisture from reaching the glass’s cold surface. A window quilt (that  is, an insulated shade) made of airtight material will do the job nicely as long  as the edge of the quilt is sealed to the window frame using bottom weights,  magnetic tape, Velcro strips, or snaps and hooks. High-insulating window quilts  are an easy do-it-yourself project — but maybe you’d prefer energy-efficient  curtains that don’t block the view, ventilation and daylight. Exterior storm  windows let you enjoy both the light and view, but they don’t resist  condensation — and they’re not cheap. Old-fashioned homemade curtains are easy  to pull aside and they’re quite affordable, but they provide negligible  insulation value. Be sure you weigh the pros and cons before making your  choice.

Before you start sewing insulated curtains or budgeting to buy storm windows,  compare a range of energy-efficient window treatments at Window Coverings and Attachments, a joint project of  BuildingGreen, Lawrence Berkeley National Laboratory and the DOE. The website is  pretty slick: The tool makes suggestions based partly on the climate and  location selected by the user. For example, in cold northern climates, moisture  condensation issues need special attention, and the wrong type of window covers  can do permanent damage. To avoid problems, you should look at window treatments  rated highly for condensation resistance, and if you indicate that you live in a  northern climate, the tool will automatically default to those options. You can  also narrow the search by your preferences. If you’re only interested in  products that will provide shade in summer, the selection tool will direct you  to those types of window covers. And it provides information on warranties to  help you choose energy-efficient window treatments that are also  durable