Window ratings — the colorful numbers, letters and insignias often placed in corners of the glass — serve as identifiers to help both homeowners and contractors identify a window’s make, model, materials and efficiency.
How is the performance of the window rated?
The performance of the window takes into account a number of factors including heat loss, solar gain and air leakage, together this creates how the information is displayed through the BFRC energy rating label as pictured above.
What are C rated windows and why are they better?
That’s why with C Rated windows, they take into account budget. Receiving some of the energy-saving benefits at a more budget-level price. The lower down the window energy rating label you go, the less energy efficient the windows start to become and perform less.
What is the best window energy rating for your home?
The lower down the window energy rating label you go, the less energy efficient the windows start to become and perform less. That’s why we would highly recommend staying above the C Rated windows if your budget allows you to do so.
What is the NFRC rating of a window?
NFRC Certification Label: The National Fenestration Rating Council (NFRC) helps consumers compare window performance through various ratings, including U-Factor, Solar Heat Gain Coefficient, Air Leakage, Visible Transmittance and Condensation Resistance. NFRC labels test standards include NFRC 100, 200, 300, 400, and 500.
What is a good energy rating on a window?
The higher the ER, the more energy efficient the window. Good performing windows and doors have an ER of 29 or higher.
What is a good air leakage rating for windows?
0.3What is a Good Air Leakage Rating? A good air leakage rating is one below 0.3. Ratings below 0.3 are recognized as energy efficient by both the NFRC and ENERGY STAR. Windows with ratings closer to 0.1 are the most efficient.
What is the difference between A and C rated windows?
The only difference between an A rated window and C rated window is that the double glazed unit used in an A rated window has a warm edge seal which gives a better thermal value.
What's the difference between A and A+ rated windows?
The difference between A and A+ rated windows are that an A-rated window will only release as much heat as they let in from outside. An A+ rated window will let in more heat from the outside than it releases from the outside. So A+ rated windows will increase the ability to gain heat from the outside.
What type of window gives best air flow?
Casement. To enjoy maximum ventilation, casement windows are your best bet. They consist of one sash that cranks open completely. This design allows them to direct and control drafts effectively, as you can utilize 100% of the window opening to expel stale indoor air.
What is acceptable leakage rate?
The acceptable leak rate does vary depending on whether the source is domestic or commercial, but a leak rate of 0.000 5 m3/h per m3 of space is generally acceptable in well ventilated areas.
Are B rated windows any good?
B Rated Windows Explained The only real difference for B Rated windows is they're not as high-performing as A Rated windows are and they're slightly cheaper to buy and install up-front. This is why B Rated windows are a great option for more cautious homeowners.
Is energy rating C any good?
A window energy rating 'C' would be far more energy efficient than an 'E' rated window. But remember, there are two methods of compliance, Energy Efficiency (WER) and Thermal Efficiency (U value). An 'E' rated window could still meet the building regulations if it had a overall U value of 1.6W/M²K.
How do I know if my windows are good quality?
The best quality windows are engineered with 100% virgin vinyl to prevent warping, peeling, and flaking from moisture damage. They also include insulated glass packages with argon or krypton gas, which helps your home stay warm in the winter and cool in the summer.
Is a higher U-value better for windows?
The lower the U-Factor, the better the window insulates. The SHGC measures how much of the sun's heat comes through the window. It can range in value from 0 to 1.
Are A+ worth more than A?
For GPA purposes, A and A+ are usually equal, but A+ is a rarer grade. Sometimes, A+ is used for 96 and higher.
Which replacement windows are most energy efficient?
Double-pane glass: this type of window is filled with inert glass and it is almost twice as energy efficient as the single-pane units. Triple-pane glass: these are the perfect replacement windows for people who want their home to be extremely energy efficient.
How many CFM do I need for a window?
This is measured by the CFM/sqft, or cubic feet per minute per square foot of window area. The CFM/sqft rating describes how much air would leak through your windows each minute at a standard windspeed. This feature is also regulated by the government, and the industry standard is set at . 30 CFM/sqft.
What is the maximum air leakage rate?
What are the maximum leakage rates? Less than four psi in one minute for single vehicles and less than eight psi in one minute for combination vehicles.
What percentage of air leakage from ducts is considered acceptable?
In summary, the standard requires that each duct system of 3000 L/s or more be tested to at least 1.25 times its operating pressure, and not leak more than 5% of the design air quantity of the duct system.
What is an acceptable leakage rate for a compressed air system?
Estimating Amount of Leakage The percentage lost to leakage should be less than 10% in a well-maintained system. Poorly maintained systems can have losses as high as 20-30% of air capacity and power.
What To Look For In a Window?
Window ratings can tell you a lot about a window. But there are a few things you should keep in mind when you are looking at prospective window installers. Always keep in mind that:
What does a higher visible transmittance mean?
Visible Transmittance – this tells you how much light the window will let in. Ranges from 0-1. A higher number means more light.
What is the most common factor in a project?
First let’s take a look at cost, as this is the most common factor among projects. Here, we will take a look at 5 window ratings by brand leaders in the industry and the estimated price range for each.
What is the U factor in windows?
U-Factor – This tells you how well the window keeps heat in. Ranges from 0.20 – 1.20. The lower, the better.
What is double glazed glass?
Glass – Double-glazed windows have two panes of glass. This includes a sealed space that’s filled with gas or air. Triple-glazed adds another layer of glass.
Why is choosing the right combination of performance and beauty for your home so important?
Choosing the right combination of performance and beauty for your home can be a nerve-wracking experience, especially because of the multitude of options available on today’s market. With an educated decision, you can enjoy worry-free maintenance and reliable performance for years to come.
How many parts are in a replacement window?
There are 6 basic parts to your replacement window:
Window Glass Ratings: Measuring Heat and Air Flow
U Factor: This rating measures non-solar heat flow through a window. NFRC ratings for U factor consider the entire window as opposed to only window glass. The lower the U factor, the more energy efficient the window.
Let the Sunshine in (or Keep it Out)
There are two measurements for visible light transmission, which measure how much visible light enters your home through a specific window. These ratings can help in selecting windows that allow more natural sun light into your home, or replacement windows capable of reducing glare.
What is the best window for a double glazed house?
For homeowners who are on a more tighter budget but want to upgrade their double glazed windows to something better that can reduce energy costs, C Rated windows might be the best option.
How does a B rated window affect the long term?
In the short term, there is a higher up-front cost in order to receive and install A Rated or B Rated windows into the property, but the long term is how much impact those windows will have in reducing energy bills, promoting heat retention and boosting sustainability and energy efficiency throughout the house.
Why are windows rated?
A Rated windows help cut energy bills and can help keep heat in the home for longer. What type of window is most energy efficient? The higher up the window energy rating (WER) label you go, the more energy efficient the window will be. No style of window is more energy efficient than the other, it’s the manufacturing process and how well ...
What does lower down the window energy rating mean?
The lower down the window energy rating label you go, the less energy efficient the windows start to become and perform less.
Why are B rated windows good?
This is why B Rated windows are a great option for more cautious homeowners. Ones who have the money to spend on new windows for their home, but don’t want to go overboard with their spending and find that B Rated windows offer everything they need in terms of spend versus cutting energy costs.
Why do you need double glazed windows?
You may think that by installing double glazed windows into your home means that your house will be warmer for longer, heating bills will be reduced and the value of your home will rise.
Why are energy efficient windows important?
Energy-efficient windows have a huge impact on sustainability and promoting heat retention throughout the home.
What is solar heat gain coefficient?
Solar heat gain coefficient (SHGC) is the fraction of solar radiation admitted through a window, door, or skylight -- either transmitted directly and/or absorbed, and subsequently released as heat inside a home. The lower the SHGC, the less solar heat it transmits and the greater its shading ability. A product with a high SHGC rating is more effective at collecting solar heat during the winter. A product with a low SHGC rating is more effective at reducing cooling loads during the summer by blocking heat gain from the sun. Your home’s climate, orientation, and external shading will determine the optimal SHGC for a particular window, door, or skylight. For more information about SHGC and windows, see passive solar window design.
What is the U factor of a window?
U-factor is the rate at which a window, door, or skylight transmits non-solar heat flow. For windows, skylights, and glass doors, a U-factor may refer to just the glass or glazing alone. NFRC U-factor ratings, however, represent the entire window performance, including frame and spacer material. The lower the U-factor, the more energy-efficient the window, door, or skylight.
What is NFRC in windows?
The National Fenestration Rating Council (NFRC) operates a voluntary program that tests, certifies, and labels windows, doors, and skylights based on their energy performance ratings. The NFRC label provides a reliable way to determine a window's energy properties and to compare products.
What is a VT?
Visible transmittance (VT) is a fraction of the visible spectrum of sunlight (380 to 720 nanometers), weighted by the sensitivity of the human eye, that is transmitted through the glazing of a window, door, or skylight. A product with a higher VT transmits more visible light. VT is expressed as a number between 0 and 1. The VT you need for a window, door, or skylight should be determined by your home's daylighting requirements and/or whether you need to reduce interior glare in a space.
What is air leakage?
Air leakage is the rate of air movement around a window, door, or skylight in the presence of a specific pressure difference across it. A product with a low air leakage rating is tighter than one with a high air leakage rating. Note that air leakage also depends on proper installation of a window, which is assumed in all ratings.
What is LSG in glazing?
Light-to-solar gain (LSG)is the ratio between the VT and SHGC. It provides a gauge of the relative efficiency of different glass or glazing types in transmitting daylight while blocking heat gains. The higher the number, the more light transmitted without adding excessive amounts of heat. This energy performance rating isn't always provided.
What type of heat transfer is used through glass?
Direct conduction and convection heat transfer through the glass or multi-layer glazing and framing
What Are Window Ratings Important?
Window ratings are directly related to the energy efficiency of a replacement window, they are the main factors which are measurable when assessing the efficiency of any window product. But why is that important? The main reasons good window ratings are important are simply because:
What are the energy ratings for windows?
This guide has explained above what each of the individual window ratings means in relation to energy efficiency, but in the real world what do you need to be looking for to get the ideal replacement window? The best window product will have an energy rating criteria of the following values: 1 A low U-factor or U-value measurement which at least below 1.25 Btu/h·ft²·°F 2 A low Solar Heat Gain Coefficient which is somewhere between 0 and 1 3 A high Visible Transmittance which is 0.20 at it’s lowest 4 A high Condensation Resistance
What happens if you use a window rebate?
If you use a window tax credit, rebate or discount then there is usually a stipulation that the product you buy meets certain energy efficiency ratings
What is the SHGC value?
The Solar Heat Gain Coefficient , otherwise known as the SHGC or Shading Coefficient (SC), measures the heat gained through the window unit by the influx of solar radiation. The construction of a good replacement window should reduce the amount of solar radiation passed through the window unit. Therefore a SHGC value of between 0 and 1 would be expected as an industry standard.
What is VT in windows?
Secondly, the Visible Transmittance, also known as the VT, is a measurement of the total visible light be can pass through the pane of glass in the window unit. In a real world situation the VT gives you a measure of how good the window will be at allowing light into the inside space, particularly helpful when you’re trying to make the most of a dark space in your home. It’s for the above reason that one would expect a good quality and high energy efficient window product to have a high VT rating value.
What is the worst thing a window unit can do?
The Condensation Resistance. One of the worst things a window unit can do is allow condensation formation on the inside of the window, in a standard window condensation formation indicates a fault in the seal. The measure of a windows ability to prevent condensation formation is known as the condensation resistance value.
What does condensation on a window unit mean?
One of the worst things a window unit can do is allow condensation formation on the inside of the window, in a standard window condensation formation indicates a fault in the seal.
What does NFRC mean?
What the NFRC Label Terms Mean. The NFRC label typically lists five measurements. The other three are somewhat less important to energy performance, according to Energy Star, but can help you judge how well a window or door will perform in a particular application — for example, whether it'll let in enough light. 1.
What is the SHGC rating?
South Central or Southern: 0.4 or less. SHGC refers to the solar radiation a window or door allows inside. Seek the lowest possible SHGC rating in warm climates to minimize the use of air conditioning.
What happens when the number of windows is lower?
The lower the number, the more condensation the window or door allows to build up.
What does "air leakage" mean?
Air Leakage. The lower the number, the more airtight the window or door. This number, expressed in cubic feet per minute per square foot of window/door area, represents the amount of air that the window or door's frame allows to pass through.
What is the energy star label?
The Energy Star label, which means the appliance has met strict energy efficiency criteria set by the U.S. government, in addition to the NFRC ratings.
What does a lower number mean?
Lower number means the room will be dimmer; a higher number means the room will be brighter. This number applies to windows or doors with windows only. Visible transmittance is the amount of light a window allows to pass through.
