Retrofit Double Glazing Windows

Guide To Energy-Efficient Windows

Windows provide houses with ventilation, warmth, and light. However, they can also impact the energy efficiency of a home in a negative way. Installing energy-efficient windows can help to reduce your home energy costs. If you are on a tight budget, it can also help to make energy efficiency improvements to the windows you already have.

How To Improve Your Existing Windows’ Energy Efficiency

There are several things you can do to improve your existing windows’ energy efficiency. They include using window coverings or treatments, weather stripping, caulking or adding on storm windows.

When storm windows are added, it can improve comfort and reduce air leakage. Weatherstripping and caulking can help to reduce air leakage around your windows. Caulk can be used for stationery joints, gaps, and cracks that are under one-quarter-inch wide. Weatherstripping can be used for moving building components, like operable windows and doors. Window coverings or treatments can help to reduce heat gain during the summer and heat loss during the winter. However, a majority of window treatment are not effective at reducing infiltration or air leakage.

Window Tips For Cold Weather

– To reduce drafts, tape clear plastic film on the inside of the window frame or use a clear, heavy-duty plastic sheet on the window frames.

– Install insulating, tight-fitting window shades on any windows that still feel drafty after they have been weatherized.

– Open your shades and curtains during the day to allow in warm sunlight and close them at night to keep out cold drafts.

– Install interior or exterior storm windows. They can reduce heat loss via windows by around 10% to 20%, depending on what kind of window has been installed on the house already. At all of the movable joints there should be weatherstripping; have overlapping or interlocking joints, and be made out of durable and strong materials.

– If necessary, weatherize and repair your existing storm windows.

Window Tips For Warm Weather

– Install white blinds, drapes or window shades to reflect heat away from your home.

– During the day close curtains on the west- and south-facing windows.

– Install awnings on west- and south-facing windows.

– On south-facing windows apply sun-control or another type of reflective film for reducing solar heat gain.

Choosing New Energy-Efficient Windows For Your Home

If your house has very inefficient or old windows, it may be more cost-effective for you to replace them instead of trying to increase their energy efficiency. Energy-efficient new windows will pay for themselves eventually through lower cooling and heating costs, and even lighting costs sometimes.

When chosen and installed properly, energy-efficient windows may help to minimize your lighting, cooling and heating costs. Improving your home’s window performance involves selection, design, and installation.


Before you choose new windows to install on your house, determine what kinds of windows are going to work the best and where the energy efficiency of your home can be improved. Understanding window energy performance ratings is a good idea so that you will know the type of energy performance ratings that are needed for your windows depending on your home’s design and your climate.

ENERGY STAR has developed criteria for minimum energy ratings by climate to label energy-efficient windows. However, those criteria don’t account for design factors of your home, like window orientation.

For passive solar house design, windows are a very important element. Solar energy is used on site for providing a home’s lighting, cooling, and heating. Strategies for passive solar design will vary depending on regional climate and building location. However, there are same basic window guidelines that should be followed – select, size and orient glass so that solar heat gain is minimized in the summer and maximized during the winter.

In hot climates, you will generally want the main glazing areas to face south so that solar heat can be collected while the sun is low in the sky during the winter. During the summer, the sun will be high overhead, so shading devices such as overhangs should be used to prevent excessive solar heat gain.

In order to be effective, the solar heat gain coefficient (SHGC) on south-facing windows should be higher than 0.6 in order to maximize the amount of solar heat gain realized during the winter, along with a high visible transmittance (VT) to allow for a good visible light transfer, and a U-factor of lower than 0.35 so that conductive heat transfer is reduced.

Windows on north-, west- and east-facing walls need to be minimized but still allow enough daylight. Whenever the sun is low in the sky, it can be hard controlling light and heat through west- and east-facing windows. Those windows should be shaded or have a low SHGC. North facing windows do not collect much solar heat and are just used for lighting purposes. Low-e (low-emissivity window glazing helps to control solar heat loss and gain in hot climates.

In cool climates, some of the most effective strategies include having south-facing windows be generously shaded and using north-facing windows preferentially. Windows that have low SHGCs reduce cooling loads more effectively.

Some kinds of glazing help with lowering a window’s SHGC and reducing solar heat gain. Low-e coatings – which are virtually invisible, microscopically thin invisible metallic or metal oxide layers are directly deposited onto the surface of the glass. They control heat transfer through a window that has insulated glazing. A large percentage of solar radiation coming through a window is absorbed by tinted glass. Reflective coatings reduce solar radiation transmission, and spectrally selecting coatings can filter out 40-70% of heat that is usually transmitted via insulated glazing or glass, while still allowing for the transmission of the full amount of light. With the exception of spectrally selective, those kinds of glazing lower the VT of a window as well.

If you are doing major remodelling or building a new home, you will want to take advantage of the chance to incorporate your window selection and design as an integral component of your whole-house design – which is an approach for building energy-efficient homes. Click here to learn more.

If you’re selling your home – find out ways to enhance the kerb appeal of your home to potential buyers in this article.


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