Last Updated: Jul 9, 2021
Windows in a home play an essential role in both your sense of well-being and the energy required to heat, cool, and light your house. On the upside: large energy-efficient windows placed generously throughout the home can bathe your home in natural sunlight. It can reduce energy demand from artificial lighting during daylight hours. They offer a biophilic architectural experience that connects your home with the surrounding natural world and even naturally warms your home with the heat from the sun. However, inefficient windows can be a significant source of heat loss and gain for your home. It will cost you money on utility bills, and negatively affect your thermal comfort.
Below, we look at the important function that energy-efficient windows play in the home and offer a complete rundown of the most energy-efficient window types for your house.
According to the U.S. Department of Energy, old and inefficient window designs can be responsible for up to 25-30 percent of all heat loss and heat gain in your home. Old, single-pane windows that you found for a bargain are most likely causing your energy bills to go through the roof.
In insulation terms, single pane glass that is only 1/4th of an inch thick will have an expected R-value of around .90. A double-pane window of similar thickness would have an expected R-value of at least 1.7 This means that you nearly double the insulation value of your windows through this upgrade. Some of the top-quality triple pane windows on the market today have an R-Value of 5, which would increase the energy performance of your windows five times over when upgrading from older, single-pane options. Even homes that undergo a complete low carbon retrofit would have a hard time achieving such drastic energy efficiency improvements. Replacing old windows, or at the very least installing window films over less energy-efficient options, is one of the best and most cost-effective strategies to improve the overall energy efficiency and thermal performance of your home.
Energy-efficient windows can also significantly reduce the amount of energy we collectively use to light our home. Unless you live in Alaska where the sun hardly moves above the horizon during the winter months, almost all areas in North America receive enormous amounts of natural light throughout the year. According to the U.S. Energy Information Administration (EIA), “the U.S. residential sector and the commercial sector used about 232 billion kilowatt-hours (kWh) of electricity for lighting. It was about 8% of the total electricity consumed by both of these sectors and about 6% of total U.S. electricity consumption.” An average U.S. home with 45 light bulbs required to use many of these lights during the daytime hours due to a lack of natural lighting in the house, adds up to an enormous amount of energy usage over a year. Proper window placement can effectively eliminate the need for turning the lights on during the daytime, and thus save you money on your electric bill.
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When searching for the best energy-efficient and high-performance windows, there are several different factors you need to focus on:
The best window options for your particular home will largely depend on the climate where your home is located and other contextual considerations. These three types of windows perform well in many types of environments.
Triple glazed vinyl windows offer perhaps the highest value in window insulation, as they incorporate insulation between all three panes. (If you are aiming for the Passive House standard, triple pane windows are a requirement.) Many manufacturers, such as the Milgard Essence Series Wood Windows, offer two separate insulating air spaces with Low E glass and dual spacers. It can interrupt wasteful heat flow through the window and thus save on heating and cooling costs. These types of windows will generally be the most expensive on the market, with an average price of between $550 and $850 USD. However, the expected energy savings, especially for homeowners upgrading from single-pane windows, can lead to relatively quick payback periods.
Wood has been considered to be the most natural and energy-efficient material for window construction. Although, the tendency for wood to expand and contract with the seasons can lead to air leakage that compromises the energy efficiency of your home. Wood also requires some sealant or finish, so any condensation does not lead to rot. Fiberglass windows are often tougher and more durable than their wood counterparts, and once installed, these framed windows will require minimum maintenance. Marvin Windows and Doors offers manufactured window frames made from Ultrex®, which they claim to be eight times stronger than vinyl and three times stronger than vinyl/wood composites. These windows can resist fading, chalking, peeling and cracking, offers unparalleled strength and durability, and also meet or exceed federal ENERGY STAR® guidelines.
Whether your budget allows you to choose between double or triple-paned windows, you should undoubtedly make it a priority to opt for gas-filled windows. As mentioned above, gas-filled windows offer increased insulation while simultaneously reducing issues with condensation. JELD-WEN® Windows offers a high-performance LoE3-366 glass with insulating argon gas to lower energy costs by assisting in keeping homes cooler in the summer and warmer in the winter. This technology also deflects direct sunlight to help reduce the fading of interior furnishings and prevent condensation. Ply Gem HP (high performance) Glass windows combine Low-E glass with argon gas fill and Warm Edge spacer options for super energy-efficient window options. This company also offers R-5 Windows, which provides some of the highest insulation capacity for windows on the market today.
So take a look at your windows today—they might be the most important element in your house.
Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.