Though energy star does not require any specific technologies, certain product features are common in many certified products. The spacer is a part of the window that separates the glazing. As a comparison, energy starrated windows typically hold an rvalue of 3. Ideally, you want your replacement windows to have the lowest ufactor rating possible, so you wont spend as much on heating bills. What is the real measure of a great replacement window. Ufactor or uvalue is also referred to as the overall coefficient of heat transfer. Apr 11, 2016 look at u factor and shgc ratings to make an informed decision on your next window upgrade. Windows can account for up to 30 percent of heat loss in the colder months, leading to an uncomfortable home and skyrocketing heating bills. Designed for new construction and replacement projects. While there are many different features that contribute to a windows overall energy efficiency, ufactor is one of the most important. How can i convert an imperial ufactor to a metric u. Well, truth is that both of these measures help your custom home windows retain energy in different ways. Lowe smartsun windows and doors feature the best heat insulation of all andersen products, with ufactors ranging from 0. The ufactor system, also known as uvalue, was created by the national fenestration rating council nfrc.
The shgc measures how much of the suns heat comes through. Draft nondefective specification requirements for u factor. The solar heat gain coefficient is a measure of how much outside heat is blocked from coming into your home. Dec 06, 20 ufactor and rvalue are also related in terms of mathematical equations.
Differentiate between nfrc and aama testing and certification processes. Looking to reduce your energy expenditure this winter. The lower the u value the better the insulation properties of the aluminium window. Understanding window ufactor energy efficiency is the number one concern for most homeowners when deciding what windows to install on their home.
But there is a way to cut costs, keep your home warm, and even make it more ecofriendlyupgrading to new energy efficient windows with a low uvalue. The latest highly insulating windows are almost as. How to read those darn window performance stickers. Energy performance ratings for windows, doors, and. Introduced in 1992, the epas energy star program has been designed to identify and promote energyefficient products to reduce. This rating measures the heat loss that occurs through the window. The two most common and recognizable energy ratings for windows and doors are u value and solar heat gain coefficient shgc. Jan 14, 2019 the prescriptive path for residential construction establishes maximum permitted u factor and solar heat gain coefficient shgc requirements for fenestration table r402.
However, one more thing to keep in mind with this value is the climate you live in. While windows are rated using both ufactors and rvalues, the ufactor is used to express the insulative value specifically of windows, while the rvalue is used primarily to rate the energy efficiency of insulation installed in other areas of the building envelope, such as beneath the roof, in the attic, behind the walls, and beneath the floors. Energy performance ratings for windows, doors, and skylights. Ufactor is the rate at which a window, door, or skylight conducts nonsolar heat flow. Ufactor represents the overall heat transfer coefficient of the window.
If this is the case, make sure proper passive design strategies are implemented thermal mass, proper shading to prevent overheating during the summer. But it also accounts for convection and radiation as well. Thus, a singlepaned window with a basic aluminum frame has a u value above 1, usually around 1. The ufactor determines how well your windows keep warm air inside. Scot hayes of new york sash talks about energy ratings on windows. Similarly, the shgc of the fenestration is to be determined in accordance with nfrc 20017 or by use of a default table. Silver line window and door nfrcenergy star information this document provides nfrc certified ufactor and solar heat gain coefficient shgc and visible transmittance vt values for silver line products along with the corresponding energy star version 6. Ufactor value on replacement windows explained royalty. Most homeowners choose to install thermal replacement windows because of the heat loss that occurs in the winter with their old windows.
U factor was well established for decades before some builders began talking about u value, apparently due to their familiarity with a related term, r value. If passive solar strategies are to be used, there may be a tradeoff with a high shgc value. The only exception to this rule are roof and skylight windows with lowe smartsun glass, which offer a ufactor of 0. Energy star qualified, windows, doors, and skylights. Ufactor windows for highperformance commercial buildings. U factor is the rate at which a window, door, or skylight conducts nonsolar heat flow. The thermal transmittance of a material such as insulation or concrete or an assembly such as a wall or window is expressed as a uvalue although the concept of uvalue or ufactor is universal, uvalues can be. Ufactor measures the rate of heat transfer and tells you how well the window insulates. To convert imperial ufactors to metric ufactors, multiply by 5.
The ufactor measures how well the window insulates. It is often the first thing consumers will look at. While windows are rated using both u factors and rvalues, the u factor is used to express the insulative value specifically of windows, while the r value is used primarily to rate the energy efficiency of insulation installed in other areas of the building envelope, such as beneath the roof, in the attic, behind the walls, and beneath the floors. R value is imperial, while rsi is metric, and both have a u value equivalent. Windows get rated by multiple factors that are important to its overall energy efficiency rating. Todays double and triplepane windows are increasingly made with an inert gas fill.
How can i convert an imperial ufactor to a metric ufactor. The only exception to this rule are roof and skylight windows with lowe smartsun glass, which offer a u factor of 0. Look at u factor and shgc ratings to make an informed decision on your next window upgrade. Ufactor gives the rate of heat transfer through the window from inside to outside when it is cold, and from outside to inside when it is hot per unit area and per unit temperature difference. Thermal transmittance is the rate of transfer of heat through matter. Ufactor and solar heat gain coefficient shgc are the two most important factors in choosing energy efficient windows. Silver line window and door nfrcenergy star information. Ufactor and uvalue are interchangeable terms referring to a measure of the heat gain or loss through glass due to the difference between indoor and outdoor air temperatures. These values are available for all vantage aluminum windows and aluminium door products as part of their wers rating. Ufactor is a term youll hear a lot when you look at windows. Uvalue the uvalue is the measure of how much heat is transferred through the window. Sep 19, 2011 scot hayes of new york sash talks about energy ratings on windows.
Hear builder matt risinger explain how the energy star program can help you maximize comfort and energy efficiency by selecting windows and doors suited to your climate zone. Ufactor, shgc, cr, vt, air infiltration what does this. In a cold climate a good u factor for a window is between 0. Several ratings must be evaluated in order to understand their true energy performance.
May 30, 2011 r value measures resistance to heat flow. While the u factor is used to express the insulation value of windows, r value is used for insulation in most other parts of the building envelope walls, floors, roofs. Heat flows from warmer to cooler bodies, thus from the inside face of a window to the outside in winter, reversing direction in summer. For windows, skylights, and glass doors, a u factor may refer to just the glass or glazing alone. Maybe it is best to give you an example of how to convert an r value of an exterior wall to a u value. The thermal transmittance of a material such as insulation or concrete or an assembly such as a wall or window is expressed as a u value. Each of these should have one consistent name, so that we all know what we are talking about. Sep 08, 2010 ufactor is a term youll hear a lot when you look at windows.
A low ufactor indicates a better insulating window. Your windows ufactor rating is expressed as btuhft. The optimal measure for your window will depend on your location. Ufactor is the mathematical inverse 1 divided by rvalue gives you ufactor, and measures the rate of that heat flow.
The lower the uvalue the better the insulation properties of the aluminium window. U value also known as u factor is a measure of heat transfer heat gain or loss through glass, while r value is a measure of heat resistance. A ufactor rating generally refers to the entire window assembly including the glazing, the frame as well as the spacer. The units for metric are wm 2k and the units for imperial are btuhrff 2. The two most common and recognizable energy ratings for windows and doors are uvalue and solar heat gain coefficient shgc. Eng712 centerofglass ufactors for all harvey windows. Nfrc u factor ratings, however, represent the entire window performance, including frame and spacer material. Im not sure i understand the focus on the word factor vs. U factor is the mathematical inverse 1 divided by r value gives you u factor, and measures the rate of that heat flow. The lower the ufactor, the better the window insulates. Ufactor this is equivalent of rvalue for insulation. Windows are often covered with coating, which is an important factor in determining. U factor is to be determined in accordance with national fenestration rating council nfrc 10017 or by use of a default table in the 2018 iecc.
U factor insulating value for windows, a principle energy concern is their ability to control heat loss. Energy stars ufactor is a number indicating how well the product insulates, to maintain interior temperatures. Lower is better with ufactorthe opposite of rvalue, when higher is better. A lower uvalue indicates better insulating properties.
The ufactor is a measure of the amount of heat thats allowed to pass through a window, measured in btus per square foot, per hour. Uvalue also known as ufactor is a measure of heat transfer heat gain or loss through glass, while rvalue is a measure of heat resistance. Low uvalue windows in maryland md low uvalue glass. While the ufactor can take any value, in general for windows it ranges from 0. In a cold climate a good ufactor for a window is between 0. Ufactor and rvalue are also related in terms of mathematical equations. Note the use of meters in the metric unit and feet in the imperial unit. Have nfrc ratings that meet strict energy efficiency guidelines set by the us environmental protection agency epa. Although the concept of u value or u factor is universal, u values can be expressed in different units. U value is a complex measurement, which is determined using a. Shgc s olar h eat g ain c oefficient is a measure of how well a window blocks out heat from the sun.
Ufactor, shgc, cr, vt, air infiltration what does this stuff. Ufactor is to be determined in accordance with national fenestration rating council nfrc 10017 or by use of a default table in the 2018 iecc. Employ at least three design options to improve window ufactor. Independently tested and certified energy performance. Silver line window and door nfrcenergy star information and data.
The cog numbers are calculated and delineated by glazing type. Ufactor insulating value for windows, a principle energy concern is their ability to control heat loss. The u factor determines how well your windows keep warm air inside. While they are related, different assumptions and test criteria are used in calculating the two values so they cannot be directly converted. While the ufactor is used to express the insulation value of windows, rvalue is used for insulation in most other parts of the building envelope walls, floors, roofs.
Ufactor, shgc, cr, vt, air infiltration what does this stuff mean. For windows, skylights, and glass doors, a ufactor may refer to just the glass or glazing alone. Environmental protection agencys epa voluntary program that helps businesses and individuals save money and protect our climate through superior energy efficiency. Ufactor is used to measure the insulation properties of windows but is not to be confused with rvalue. If you know a windows ufactor, you can figure out its rvalue. By increasing the rvalue from 3 to 5, average heat loss through the window is reduced by 30 percent to 40 percent. Lowe smartsun windows and doors feature the best heat insulation of all andersen products, with u factors ranging from 0. Identify five attributes affecting window u factor. Lower is better with u factor the opposite of r value, when higher is better. Employ at least three design options to improve window u factor. The national fenestration rating council nfrc uses the uvalue or ufactor as the standard rating metric on windows and doors.
Epa requires that the ufactor for energy star labeled products is certified and listed on the product label. A u factor rating generally refers to the entire window assembly including the glazing, the frame as well as the spacer. Dec 20, 2011 as a comparison, energy starrated windows typically hold an rvalue of 3. The latest highly insulating windows are almost as efficient. And because this measures the rate at which a product transfers heat, lower uvalues mean better insulation and help protect the building envelope. Most windows now carry this rating so its becoming easy to. The uvalue or ufactor measures how much heat a window, including the frame, glass, and insulating materials, allows out of the house, which is also known as its thermal transmittance. Heat loss through the frame can be significant, up to 15.
Pgt builds custom aluminum, vinyl and impact resistant house windows, doors and porch enclosures. The u factor is the rating most homeowners look at first and for good reason. So what exactly does it mean and what is a good or bad ufactor. Nfrc ufactor ratings, however, represent the entire window performance, including frame and spacer material. A common comment i get is your window has a u value of 1. Designed for new construction and replacement projects, the windows can achieve a ufactor as low as 0. For superior energy performance, use windows with a ufactor of 0. Ufactor can be expressed in metric units wm 2 k or imperial inchpound units btuhft 2 f. U value the u value is the measure of how much heat is transferred through the window.