Understanding Window R-Value and U Value When Remodeling
Here in Michigan, it is important for comfort and efficiency to keep the cold out of our homes in winter. When it comes to energy efficiency, your windows play a big part in your usage, and utility bills. Depending on the season, your windows can be a source of heat loss or gain. Double or triple paned windows can significantly improve your energy efficiency. Today, new types of high-performance glazing are also available that can make windows resistant to heat loss, heat gain, and other problems. When it comes time to remodel your home or if you are considering a new addition, work with your project manager or designer to find the best R-Value and U-Value windows possible at a price point that fits your budget.
In terms of measuring a windows performance, there are two numbers that you should understand; they are R-values and U-values. Other window performance measurements include UV value which measures the amount of ultraviolet light that is admitted, a “light-transmittance” value that rates how much light allowed in, and a “shading coefficient” that measures the amount of glare allowed.
Energy efficiency in new or replacement windows can vary widely. There are many factors that determine efficiency including the materials used in construction, the number of panes of glass, the gas used to fill the panes and the installation of the windows themselves. This is why there are two main heat loss valuations you need to consider when buying windows; R-value and U-value. Windows that are most efficient will have a high R-value and a low U-value.
The Definition of R-Value
R-value is the measure of a window's thermal resistance to heat flow. The higher the R-value, the more insulating ability the material has. A single glazed window offers an R-value of R-1 or less; a double glazed window provides an R-value of R-2. The type of glass that is used in a window has a critical function when awarding R-values.
The Definition of U-Value
When measuring heat loss, U-value is a time factor measurement. The U-value reflects the measure of heat loss a window experiences in one hour. Windows will typically have two separate U-values: one for the glass and one for the entire window including the frame. The lower the U-value, the more energy efficient the window.
As a general rule, if you live in a climate that experience extended cold weather and want to improve energy efficiency, look for a high R-value. Speak with your contractor. They will have an understanding of the best window for your local climate.
Window Glass Choices
Manufacturers today are producing a number of different energy efficient choices for glazing. Today, the typical window is double glazed separated by an air space filled with an inert gas, typically argon or krypton. Here are some of the most popular choices that can meet your specific needs.
Tinted and Reflective Glass
Tinted glass reduces heat and glare from direct sunlight. It also reduces UV rays. Tinted glass is darker than clear glazing, and if the light transmittance is an issue, it may not be the best choice for you. Like tinted glass, reflective glass reduces solar glare, and offers some privacy as from outside; it appears to be a mirror.
Typically used in sliding patio doors, most local business codes require safety glass for some applications. When replacing windows, make sure to consult your local building department to ensure they meet all local codes. Your contractor will understand your local building codes and can help you make the proper choices to ensure compliance.
Insulating and Low-E Glass
This glass uses a micro-thin metallic coating that blocks radiant heat transfer. It also significantly reduces UVA and UVB rays which protects your furniture, carpets, and fabrics from fading. Some manufacturers offer products that have an incredible R-8 value.
Multi-pane windows can have either real or faux divided lites (or panes). Depending on the architectural style of your home, multi-pane windows can be an excellent choice, especially if you live in a traditional style home. Real muntin bars–the dividers in a window–are more expensive than snap-in grilles and a more difficult to keep clean.
Today, you have a wide variety of choices when it comes to replacement or new construction windows. There are some great options out there including windows and doors with internal shades, or mini blinds between the panes. There a great option for controlling glare and heat gain on a sunny summer afternoon.
You can significantly improve your home's energy efficiency, lower your utility bills and protect your valuable artwork, fabrics, carpet, and furniture with the proper window. A professional design-build-remodel firm can work with you to help you choose the correct windows for the Michigan climate and the architectural style of your home remodel.
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Forward Design Build is a residential design-build firm in Ann Arbor, Michigan that is known for its commitment to craftsmanship and communication. We are committed to improving our neighbors quality of life with inspired design and creative remodeling. Our homes are highly functional, exquisitely beautiful, and remarkably comfortable. Contact us to speak with an expert about your new home or remodeling project.