Council: RPC - Residential Products Council

What benefits are there to residential windows?

Windows add architectural beauty, energy efficiency,  daylighting and natural ventilation.

Think of the windows as the eyes of the house. They’re one of the few things that are seen from both a home’s interior and exterior. Residential windows add architectural interest to your home inside and out, accenting it and framing it, like pictures on walls. Plus, windows allow you to enjoy the view from the comfort of inside your home, no matter how hot, cold, rainy or snowy it is outside.

Residential windows are a reflection of your home, its style, and ultimately, your sense of style. What do your windows say about you and your home? Are they stylish, energy efficient and in good condition, helping seal out air and moisture, keeping your home warmer in the winter and cooler in the summer? Or are they in need of repair or replacement? If your windows are worn out, drafty, leaky or inefficient, the good news is that windows can be replaced with more energy efficient options.

Today’s residential windows offer superior design and energy efficiency.

For more information about these topics, visit the Benefits of Energy Efficient Windows and Design Considerations pages on the Efficient Windows Collaborative website.

What is fenestration?

Today, residential windows are also sometimes called fenestration products. Fenestration refers to the arrangement, proportioning and design of windows, doors and/or skylights in a home or other building type. The word fenestration comes from the Latin word “fenestra” for “window.”

When should windows be replaced?

If the windows in your home are leaking air or water, assess the window to see if it needs to be repaired, retrofitted or replaced. Likewise, if your windows are fogged up between the panes of glass, this may be a sign that the seal has failed, and the window may need to be repaired or replaced to provide a clear view.

If you have single-pane windows, condensation will form more frequently than double or triple-pane windows that provide more insulating value between your home’s interior and exterior surfaces than the single glass surface in single-pane windows.

What construction types use residential windows?

You’ll find residential windows used in a variety of construction applications, ranging from wood frame to brick, masonry, block construction and/or other materials.

What are the key components of a residential window?

Today’s residential windows offer a myriad of style options to enhance your home’s design and performance. In describing residential windows, there are several key components, such as the sash, frame, spacer, and glass.

Cap stocks or coatings can provide various color options on the profile of a residential window. Think of a cap stock like a cap on a tooth—it covers what’s underneath. The same goes for a coating. It covers what’s underneath, like the substrate or base material from which the window is made. Coatings are used on all materials (aluminum, fiberglass, vinyl and composites).

The frame refers to the material that literally frames or holds the glass and/or sash in place in a window. Window frames can be made from a variety of materials, like aluminum, vinyl, fiberglass, wood or combinations of materials. Residential window frames can also include various profile shapes to replicate the architectural detail of a historic look or a modern, contemporary look.

The sash refers to the moveable part of a window. Sashes may crank out, or move horizontally or vertically to open a window. Sashes often open to the exterior of a building, but some window designs, like those popular in Europe, may allow a window to open into the home.

The glass that is visible within the frame or sash can be a single pane or a more efficient multiple pane construction known as an insulating glass unit (IG). Spacers are used to separate the panes of glass in IGs and are bonded together using sealant materials.

What materials are residential windows made from?

Today’s residential window frames and sashes are made from a wide range of materials including aluminum, composites, fiberglass, vinyl, wood or combinations of materials sometimes referred to as hybrid windows. Standard clear, high-performance coated, tempered, tinted and laminated glass options are available.

Depending on the material they’re made from, some residential windows, like wood windows, can be purchased unfinished, to be painted, stained or sealed on the job site. Some residential windows, like vinyl windows, can include factory-applied films that replicate the look of wood grain or metallic finishes.

Fiberglass windows are often factory-finished, reducing the need for painting on the job site. Vinyl windows require no additional finishing. Some vinyl windows are available with painted exterior or interior finishes to expand available color options for the homeowner. Aluminum or aluminum-clad windows can take on a variety of exterior colors to suit a home’s exterior style.

FGIA includes councils dedicated to the advancement of those materials including:

• Aluminum Material Council (AMC)
• Fiberglass Material Council (FMC)
• Vinyl Material Council (VMC)
• Wood and Cellulosic Composite Material Council (WCCMC)

Do industry standards and certification programs help shape product performance?

Whether its spring rain, summer heat, or winter winds, residential windows are designed and tested to meet, air, water and structural performance standards. For example, NAFS (North American Fenestration Standard) is a recognized industry program that defines residential window performance to withstand weather conditions.

The AAMA certification program certifies windows, doors and skylights to an industry standard that sets minimum performance levels for air infiltration, water penetration and structural performance.

What’s your style?

Whether you live in an historic home and are seeking to replicate the architectural style of an earlier era, or you wish to convey a contemporary look to refresh the look of your home, you’ll find a type and style of residential window to suit your design and budget.

A wide range of residential window types are available today

Residential window styles often used in homes today include double-hung, single-hung, slider, fixed, or casement windows, sometimes called crank out windows because the hardware literally cranks out a window sash to open it.

In a double-hung window, both sashes move up and down vertically to allow for ventilation. In a single-hung window, the top sash is permanently fixed in place, and the bottom sash opens and closes vertically to allow for fresh air flow. In double-hung windows, the top sash can be lowered to let heat out, or to allow fresh air in, for ventilation options, like in a home with young children present. Simply lower the top sash of a double-hung window for air flow and keep the bottom sash closed. Or if you choose, raise the bottom sash to allow in fresh air.

Slider or sliding windows feature a sash that opens and closes by moving horizontally, from side-to-side to open and close.

Other types of residential windows include awning windows in which the sash lifts up and out like an awning. Hopper windows are those that tilt in, like the type of windows sometimes used in basement applications, or in window groupings.

Tilt and turn windows feature moveable sashes that literally tilt and turn to open. This design is popular in Europe and is also available in the United States today.

Projection windows push out to open up to allow fresh air flow into a home. Think of them like a pop-out camper, since they pop out to open up a room to fresh air.

Clerestory windows are those often placed out-of-reach of the occupants in a home, but which invite in natural light while adding design interest. These windows may be in the upper level or a two-story room, or near the ceiling of a room.

Garden windows project outside a home’s walls and often include shelves in which plants can be set to soak up the sunlight.

Radius or circlehead windows are those that are curved in shape, like that of a half-circle.

Eyebrow or arch-topped windows are those whose curved topline shape resembles that of an eyebrow or an arch.

Transom windows may open to let in fresh air or be permanently fixed in place. They are typically installed above other windows or doors, to give the illusion of larger windows, or to create the look of a window wall. Transom windows are also sometimes installed over doors, as in older homes with taller ceiling heights to allow for air flow from room to room.

Bow or bay windows extend at angles outside of a home’s walls to add architectural interest. The difference between a bay and a bow window is the degree of angles. Bay windows often include greater angles and typically range from two to three or four windows. Bow windows curve more gracefully at smaller degree angles and feature more windows. Bay or bow windows may also include a window seat or space to display your favorite items inside the home.

Patio doors are often included with residential windows to provide a uniform look and functional access to outdoor living areas.

Window Mulling

Window mulling refers to the process of joining two or more windows together. This may be done in the factory, or on a job site as a home is constructed, remodeled, or its windows are replaced. The benefit of mulling, or joining windows together is to create a larger focal point and natural light in the home, like in the case of a group of windows in succession to frame a fantastic view, or to create architectural interest in a great room, a living room, a foyer or other area of the home. Because of the weight of glass and manufacturing equipment and shipping size limitations, there’s often a limit to how large a single window unit can be and remain structurally sound. Mulling, or joining groups of windows together allows you to maximize your view, while maintaining your home’s structural integrity and residential window product performance.

The rating of mulled combinations may be lower than the individual unit rating. It is important to verify that the mulled combination rating meets your project’s building code requirements.

Some windows include exterior cladding

Some windows also feature exterior cladding—a covering or “skin” like those made of aluminum or vinyl, applied over the window frame and or sash, to help protect exterior surfaces from environmental conditions, or for aesthetic purposes. For example applying aluminum cladding over a wood window helps provide added protection with a wide range of exterior color or texture options for design appeal.

Wood windows made from a range of species

Wood windows can be made from a variety of species of woods, from readily available renewable resources like pine, a soft wood, to hardwoods like oak, cherry, or mahogany, or other woods. Modern wood windows are typically factory treated for added protection against damage from moisture or insects.

Window laminates offer unique looks, plus help protect from elements

Laminates can also be applied to residential window sashes and frames to provide different looks. For example, laminates can provide the look of simulated wood grain, to various color or texture options. For example, a solid-colored laminate could be featured on the exterior of a window, with a wood-grain effect, an embossed texture, or a metallic look on the interior. In addition, laminates applied on residential window framing material can help protect against dirt, chemicals and environmental pollutants.

Window hardware options abound

Hardware is used to open, close and lock residential windows, or to provide decorative accents. Residential window hardware comes in a variety of styles and finishes, including some specialized options, like automatic-locking window hardware, or that which is easier for those with limited mobility to operate. For example, some hardware is designed for easier use by the elderly, or those with arthritis.

Double-hung windows may include sash lift hardware options. Sash lifts are handles placed on the interior of the lower sash of the window that make it easy to grip the lower sash to open and close it. Plus sash lifts often replicate the look of earlier eras in architectural design. Some hardware, called spoon hardware because its shape literally resembles the bowl of a spoon, is another option available to add a historic look to today’s windows.

Some windows can be equipped with egress hardware, allowing for a wider opening of a window unit. Check with your local building code officials to learn more about egress requirements for your home’s area.

Optional hardware also includes window opening control devices (WOCD) to help prevent accidental falls through windows, and other devices that simply limit the window from opening greater than four inches.

Consider the window warranty

Before you consider after-market options to your windows such as window films, thermal blinds, etc., consult the warranty of your window manufacturer. Keep in mind that some after-market products may void the original window manufacturer’s warranty, so consult the window warranty before you modify the window or its performance.

Decorative elements accent the look of residential windows

Residential windows can include grilles, sometimes also called grids or muntins. These create the look of individual panes of glass, but provide greater energy efficiency than single panes of glass connected together.
Grilles can be permanently applied to the exterior and interior of window glass, be permanently placed and sealed between panes of glass, or be removable.

When grilles are placed between panes of glass, it makes it easier to clean a window’s interior and exterior glass surfaces, compared with cleaning smaller, individual panes of glass separated by a grille or framing material.

Glass options can improve energy efficiency, privacy, reduce sound

Residential windows are available with a variety of glass, often called glazing options, like low-E (low emissivity) insulating glass, obscure glass or clear glass. Other types of options include double- or triple-pane insulating glass options, tempered or safety glass, or impact-resistant glass for security or hurricane zones.

Obscure glass may be frosted glass or textured (patterned) to help provide privacy, for example, in bathrooms or exterior doors.

Clear glass is a basic option that does not incorporate coatings to help improve a window’s energy efficiency. Clear glass allows heat and the sun’s rays pass through the glass, which can fade interior furnishings and reduce a home’s energy efficiency.

The type of glass used in residential windows can also impact daylighting. For instance, in the south, better glare control and lower levels of transmitted light may be desired. Certain low-E glass products help control bright light and glare. View the daylighting page for more information.

Screens help keep insects out

Residential windows may feature screens to help keep insects out of a home. Keep in mind that insect screens are not designed to withstand the weight of a person, so don’t lean on screens and keep child’s play away from windows, for safety’s sake.

Screens may be installed on the exterior of a window, as is often the case in double-hung windows, or on the interior of a window, as is typical for casement or crank out windows. Some screens are known as disappearing screens, because they roll out of sight when not in use, or because the screen material is so transparent is appears to be virtually invisible.

Screens may also be applied to the exterior of a window to help control light or the reflection of it.

Many types of screen materials are available for residential windows, ranging from aluminum, to fiberglass, to other transparent screen materials.

The sounds of silence

Residential windows can also help reduce sound transmission, providing peace and quiet and peace of mind inside your home. The STC rating stands for sound transmission class. What that means is the window’s ability to help reduce outside sounds is evaluated. Refer to AAMA 1801 for more details.

OITC stands for outdoor indoor transmission class, similar to STC, but based more on typical outdoor sound frequencies. STC relates to indoor sound levels. STC is more commonly known, but OITC is a newer rating system that’s increasing in prominence.

Outdoor sound frequencies span the range of low frequency sounds, like the rumble of a dump truck, the sounds of aircraft overhead, or a bass from a car’s stereo system.

Improved indoor air quality

Residential windows also impact indoor air quality, helping keep out dust and dirt. Plus, the type of windows that open, called venting windows, help refresh a home when they’re opened to welcome in fresh air.

Beautiful, durable finish options to choose from

Residential windows include a variety of factory-applied exterior finishes, like those for specialized corrosive conditions caused by salt water sprays in seacoast applications, or other harsh environments.

Other types of finishes include factory prefinished options applied to wood, fiberglass, vinyl, or aluminum windows. Finishes for residential windows can range from paints or stains, to other types of coatings.

Depending on the material they’re made from, some residential windows, like wood windows, can be purchased unfinished, to be painted, stained or sealed on the job site. Some residential windows, like vinyl windows, can include factory-applied films that replicate the look of wood grain or metallic finishes.

Fiberglass windows are often factory-finished, reducing the need for painting on the job site. Vinyl windows require no additional finishing. Some vinyl windows are available with painted exterior or interior finishes to expand available color options for the homeowner.

Windows can serve as emergency exits

In the event of an emergency, like a fire, windows can serve as a way to exit a home or for rescue workers to enter it.

Larger-sized windows that meet codes for emergency escape and rescue requirements are called egress windows.

Egress windows are sized to provide emergency escape and rescue access for you to exit your home quickly in an emergency. Egress windows also allow access for rescue workers to gain entry, even when wearing bulky safety gear like oxygen tanks. Bedrooms or sleeping areas should contain egress windows or exterior door. Egress windows can be any type of operable or venting window that opens. The specific location of a window in your home, and your building codes determine what size of an egress window is needed for each respective location in your home.

Consult with your local code officials for specifics on code requirements in your area. If you remodel your home to include a basement bedroom or sleeping area, or you transform your basement into a finished basement, consult your local codes to see what’s required in terms of egress windows.

Enhancing safety, security

Residential windows are designed and tested to enhance safety and security.

For example, if you live in a hurricane-prone region, residential windows can include an option called impact-resistant glass. This specialized laminated glass helps resist airborne objects from penetrating it. The impact-resistant glass is designed and tested to help stay connected to the window frame, to help protect a home and its contents, to help a building stay intact in a storm. This is an obvious advantage over shutters or even plywood applications, allowing the occupant to see out and also allows daylight in during electrical power failures. This type of glass can also be used in other types of applications such as for increased security or outside noise reduction and even golf balls.

Some types of residential windows are tested to meet tornado standards in addition to hurricane conditions.

Window Safety Task Force

FGIA is a member of the National Safety Council’s Window Safety Task Force. The group educates consumers on home safety topics related to windows. For more information on window safety, visit our Window Safety page.

Saving energy, adding comfort

Most energy-efficient residential windows offer double- or triple-pane insulating glass options. Insulating glass often includes an odorless, colorless inert gas, like Argon, that’s placed between the panes of glass to increase the window’s insulating value, helping keep your home warmer in the winter and cooler in the summer.

An easy way to choose energy-efficient windows is to look for products that meet ENERGY STAR^® requirements. In the United States, the ENERGY STAR program was created by the U.S. Environmental Protection Agency and the U.S. Department of Energy to help consumers identify windows and other products that save energy.

ENERGY STAR is a voluntary program in the U.S., and in Canada, which recognizes windows, doors and skylights that are highly energy efficient.

The ENERGY STAR certification criteria is based on designated ENERGY STAR climate zones. Because their climates differ, so do ENERGY STAR zones and product certification distinctions in the U.S. and Canada.

For more information on the ENERGY STAR program in the United States, visit: energystar.gov

For a link to information about ENERGY STAR in Canada, visit: ENERGY STAR Canada

For more information on windows and other products designated as “Most Efficient” by ENERGY STAR, click here.

Low-E glass enhances energy efficiency

Residential windows with low emissivity glass (typically known as low-E), perform multiple functions. It is designed to allow visible light transmission while reflecting UV (ultraviolet) and IR (heat) from the solar spectrum. For instance, it reflects the sun’s harmful rays, helping protect your home and furnishings from fading while keeping your home cooler in the heat of the day.

Low-E glass also helps to keep your home warmer in the winter, reflecting the heat that’s inside your house back into it, to enhance thermal performance and reduce energy loss. Windows with low-E coated glass also allow visible light to stream into your home, without obstructing the view. Low-E glass helps homeowners save energy in their own home and helps reduce energy consumption as a whole, which saves money on utilities.

Insulating glass enhances energy efficiency

Insulating Glass (IG) consists of two or more panes of glass to help increase energy-efficiency as compared to windows with a single pane of glass. Factory-assembled IG units reduce the potential for moisture or fogging to occur between the panes of glass. Fogged units obscure the view through the window. Insulating glass units may or may not include an inert gas, like Argon, or other odorless colorless gasses, contained and sealed in the IG to improve the IG unit’s insulating properties.

What does U-factor mean?

U-factor, sometimes also referred to as U-value, is used to describe the insulating performance of windows. The lower the U-factor or U-value, the better the product’s insulating value. U-factors, or U-values, are the reciprocal of R-value, like commonly found on wall or roof insulation products — the higher the R-value, the better insulation in the walls and ceilings. To estimate the R-value of a window, calculate 1 / U. Example: U-factor is 0.28, R-value is 1 / 0.28, or 3.6.

A low U-factor, or U-value, is important in all climates. In Southern climates where air conditioning is important, a lower U-factor will save money by allowing less of the cool air to be lost to the outside of the house. Additionally, choose a window with a lower solar heat gain coefficient (SHGC) to block more of the sun’s heat rays.

What is solar heat gain and how is it measured?

Solar heat gain is how much heat passes through a window because of the sun’s rays shining on it. The Solar Heat Gain Coefficient (SHGC) is a measurement of how well a window product blocks heat from the sun. The lower a product’s SHGC, the less solar heat it allows to enter a building.

Daylighting is a term used to describe the amount of natural light passing through a window, door or skylight. Daylighting is impacted by the size, placement and type of windows in a home or other structure. Daylighting helps reduce the need for artificial lighting in a home, therefore saving energy. If you want to experience the benefits of daylighting and a view, you need a window to enjoy the view outside from the comfort inside your home.

If you live in a Northern climate, you can bask in the comfort of an outdoors view while remaining inside your home when the temperature plummets outside, because a residential window is helping keep the cold out and the warmth inside. Likewise, residential windows with low-E or low emissivity glass can help reflect the sun’s rays in the hottest part of the day, helping keep the home cooler in the summer. Types of glass options used in residential windows can help reduce solar heat gain, help you save energy and save on cooling costs.

What is Visible Light Transmittance (VT)?

The fraction of light that passes through window’s glass is known as Visible Light Transmittance (Tvis or VT). Visible Light Transmittance (VT) measures how much light comes through a product expressed as a value between 0 and 1. The lower the number the less of the sun’s visible light that is transmitted, where 1 would be the same as being outside in the sunshine and 0 would be total blockage of all light.

Designed and tested to provide weather-tight performance

Residential windows are designed to help keep out the elements, whether it’s heat, cold, rain, wind, dirt, hail or snow.

Residential windows are tested to evaluate air, water, and structural performance. What that means is residential window testing evaluates a window’s ability to help keep wind, rain and other types of moisture outside a home, while maintaining the strength and structural integrity to keep the window opening itself intact.

About AAMA testing and certification programs

Residential windows are tested to simulate a variety of conditions your home may be subjected to, like how much air is kept out of your house in a high wind situation, or how much heat is kept out on a sizzling summer day.

Since 1962, AAMA Certification, the original third-party window performance program, has provided manufacturers with the means to independently demonstrate product performance to their customers.

The AAMA Certification Label tells customers that a sample of the product has been verified as conforming to the standards’ requirements through independent laboratory testing and follow-up on-site inspection of the manufacturer’s production line.
View window safety brochures.

Regardless of the type or style of residential window you choose, or what company manufactures or sells it, it is important to install the window properly for best performance. Whether you install the window yourself or it’s installed by someone else, follow the manufacturer’s installation instructions. Or, if the manufacturer doesn’t offer window installation instructions, use InstallationMasters^® as a guide.

For example, windows should be set in openings that are plumb, level and square, to allow a window to open and close properly, and maintain their shape best over time.

Observe regulations like EPA’s Lead Renovation, Repair and Painting (LRRP)

In homes built in the U.S. before 1978, the Environmental Protection Agency (EPA) requires that certain precautions be taken to minimize the potential spread of lead residue from painted surfaces during the remodeling or replacement process.
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The InstallationMasters Program

FGIA offers an InstallationMasters program to train window and door installers. It’s important to understand the importance of properly installed products to ensure best performance.
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Condensation on the interior or exterior surface of the glass generally occurs when excessive moisture or humidity in the air comes into contact with a cooler glass surface and may not mean that the window needs replacement.

Interior condensation

When interior humidity is high and the outdoor temperature is low, condensation can occur on interior glass surfaces. To help protect your home and home furnishings, reducing the relative humidity indoors to lessen interior moisture helps alleviate interior glass condensation. Also consult with experts to help ensure that your home has an adequate ventilation system. To temporarily reduce interior condensation, like after a shower, turn on an exhaust fan or open a window to assist with moisture escape.

To better understand indoor condensation visit our Understanding Indoor Condensation web page.

Exterior condensation

One way exterior condensation on windows can happen is when the glass temperature is below that of the outside temperature, like on a hot humid day. When differences in interior and exterior temperatures and high exterior humidity levels occur, moisture condensation can build up on the exterior surface of the glass. It’s the same type of condition that causes a cold glass of your favorite drink to sweat on a hot summer day.

Another way exterior condensation can happen is when environmental conditions outside promote condensation on the glass. Highly insulating glass units allow the outside pane to be colder than the inside pane. If the outer pane is colder than the dew point of the air, condensation will occur. This could happen even when it isn’t that cold outside. This usually occurs when there is little or no wind or air movement and is more likely during the early hours of the morning. A similar example is the windshield of a car left outside overnight, which develops condensation in the early morning.

Tips for caring for and maintaining your residential windows

To help you care for and maintain your residential windows, see this FGIA guide for more tips.

To some extent, every home, regardless of age or location, needs to “breathe.” You may feel some air coming into your home around windows, doors, skylights, electrical outlets, walls, floors or the roof. This is air infiltration, and it is the result of air pressure differences between the inside and outside of the home. Every home has some level of air infiltration. Glass surface temperature, by itself, is not an indication of air infiltration.
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These guides have been prepared to assist architects and specifiers in selecting windows and doors to meet the requirements for specific jobs and conditions. Performance requirements and basic test methods, as recommended by AAMA, are also reviewed.
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