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Windows 2018-10-06T11:47:59+00:00

The Anatomy of Different Window Styles

A lot of consideration needs to be put into the style of window one chooses for each application.

There are numerous considerations.

  • Operating characteristics
  • Size considerations
  • Design issues
  • Energy usage considerations
  • Allowable sunlight
  • Structural performance issues

Here is a list of the type of window styles commonly available and an evaluation of each.

Casement Windows

Operating characteristics:

A crank operator is screwed to the sill of the frame. The crank pushes one or two bars connected to the sash and which twist the sash from an at rest position inside the frame to a maximum at rest position perpendicular to the frame. Many operators move the sash so that small space is accessible between the sash and the jamb (side) of the frame to allow for access of the exterior side of the glass in the sash for cleaning purposes.

Hinges connect the top and bottom of the sash to the frame.

On the side of the frame where the sash projects out, there will be one or more locking handles that engage with hardware on the sash to lock the sash when closed. Small windows may have a single locking handle connected to a single point on the sash. Larger windows may have multiple handles, each connected to a single point on the sash. A multipoint locking system allows a single handle to control multiple locking points on the sash.

Size Considerations:

The amount of weight that can be handled over the long-term by casements is limited by the strength of the hinge. Casements have maximum widths and height based on this engineering consideration. Maximums will be significantly shorter for triple glazed windows because of the additional weight of 50% more glass.

Design issues:

The clean lines of a casement are one reason for its growing popularity. They are considered more modern in appearance then the more traditional double and single hung windows that one finds in everything from farm houses to Victorian mansions. In essence, a casement is a small picture window, maximizing the center view and natural light penetration. Casements both operate and look best when the window has the popular vertical proportions often referred to architecturally as ionic design. An ideal might be a width of ‘X’ and a height of ‘X times 1.6’. There is room in this formula for some variation. Casements easily allow for the sash to be positioned to directing air flow.

Energy usage considerations:

Of all the operating windows, casements are at the top of limiting air infiltration, which is a factor in energy usage. Many casements (certainly the ones available at GEM) are designed to handle a 1 3/8” thick triple glass which can allow for up to an R9 center of glass. Energy efficiency is the nickname of a casement! You may see sliding windows with a better Energy rating (E.R.) than a casement. This is due to the slimmer lines of a slider allowing for more sunlight to enter through the window. More sunlight means a higher solar heat gain coefficient (SHGC). Solar heat gain does not impact on thermal efficiency, so it doesn’t improve the U (or R) value of a window, but it is part of the formula for an E.R. This can be somewhat misleading, particularly when you think you’re buying an energy efficient window and you may not want the solar heat part of the E.R.’s energy efficiency. This is a perfect segue into our next topic.

Allowable sunlight:

As noted, sliding windows tend to allow more direct sunlight, however, the cleaner lines of a Casement may appear to be bringing more light into a room.

Structural issues:

What is structural performance? It is the ability of a window to resist bowing or breaking under intense window pressure. A window with poor structural performance, when under pressure, will deflect to the point where it may allow excessive air leakage or water penetration. Happily, quality casements (Yes, like the ones at GEM.) tend to have excellent structural performance.

Awning Windows

  • Operating characteristics:

A crank operator is screwed to the center of the sill of the frame. The crank pushes a scissor bar connected to the sash and which pushes the bottom of the sash from an at rest position inside the frame straight out to a slanted position. In order to clean the exterior glass from the inside, the scissor can be disconnected, allowing the sash to go into a horizontal position so the exterior glass is on top.

Hinges connect the sides of the sash to the frame.

There will be locking handles on both sides of the frame that engage with hardware on the sash to lock the sash when closed. Most windows will have a single locking handle connected to a single point on each side of the sash. Larger windows may have a multipoint locking system that allows the single handle on each side to control multiple locking points on the sash.

  • Size Considerations:

The amount of weight that can be handled over the long-term by awnings is limited by the strength of the hinge and the weight placed on the horizontal of the sash. Awnings have maximum widths and height based on this engineering consideration. Maximums may be significantly shorter for triple glazed windows because of the additional weight of 50% more glass.

  • Design issues:

The clean lines of an awning combined with the fact that it can often be used to replace a horizontal sliding window are reasons for its use. They are considered more modern in appearance then the more traditional double and single sliding windows that one finds in the typical sub-division sides and backs. In essence, an awning is a small picture window, maximizing the center view and natural light penetration. Awnings both operate and look best when the window has a balanced horizontal proportion. An ideal might be a width of ‘X times 1.6’ and a height of ‘X’. There is room in this formula for some variation. Awnings get air flow from the bottom. A limitation is that one is always looking through the glass.

  • Energy usage considerations:

Of all the operating windows, awnings, like casements, are at the top of limiting air infiltration, which is a factor in energy usage. Many awnings (certainly the ones available at GEM) are designed to handle a 1 3/8” thick triple glass which can allow for up to an R9 center of glass. Energy efficiency is the hallmark of an awning! You may see sliding windows with a better Energy rating (E.R.) than an awning. This is due to the slimmer lines of a slider allowing for more sunlight to enter through the window. More sunlight means a higher solar heat gain coefficient (SHGC). Solar heat gain does not impact on thermal efficiency, so it doesn’t improve the U (or R) value of a window, but it is part of the formula for an E.R. This can be somewhat misleading, particularly when you think you’re buying an energy efficient window and you may not want the solar heat part of the E.R.’s energy efficiency. This is a perfect segue into our next topic.

  • Allowable sunlight:

As noted, sliding windows tend to allow more direct sunlight, however, the cleaner lines of an awning may appear to be bringing more light into a room.

  • Structural issues:

What is structural performance? It is the ability of a window to resist bowing or breaking under intense window pressure. A window with poor structural performance, when under pressure, will deflect to the point where it may allow excessive air leakage or water penetration. Happily, quality awnings (Yes, like the ones at GEM.) tend to have excellent structural performance.

Fixed Casement Windows

  • Operating characteristics:

A fixed casement has no operating characteristics because it does not open.

  • Size Considerations:

Of all window styles, a fixed casement can handle the most weight, making larger windows with triple glass possible.

  • Design issues:

The reason it is called a ‘casement’ is because it has the same appearance as a casement so that it can be used in combinations to keep the horizontal lines straight. This is a cleaner look and makes grills line up properly.

  • Energy usage considerations:

Fixed casements (and picture windows) are at the top of limiting air infiltration, which is a factor in energy usage. GEM fixed casements are designed to handle the 1 3/8” thick triple glass which can allow for up to an R9 center of glass. Energy efficiency and a very high Energy Rating are facts with a fixed casement. You may see a picture window with a better Energy rating (E.R.) than a fixed casement. This is due to the slimmer lines of a picture window allowing for more sunlight to enter through the window. More sunlight means a higher solar heat gain coefficient (SHGC). Solar heat gain does not impact on thermal efficiency, so it doesn’t improve the U (or R) value of a window, but it is part of the formula for an E.R. This can be somewhat misleading, particularly when you think you’re buying an energy efficient window and you may not want the solar heat part of the E.R.’s energy efficiency. This is a perfect segue into our next topic.

  • Allowable sunlight:

With no center barriers, fixed windows allow the same amount of light as a casement, but because they can be a lot larger, there is more potential for sunlight.

  • Structural issues:

What is structural performance? It is the ability of a window to resist bowing or breaking under intense window pressure. A window with poor structural performance, when under pressure, will deflect to the point where it may allow excessive air leakage or water penetration. Happily, quality fixed casements (Yes, like the ones at GEM.) tend to have excellent structural performance.

Picture Windows

  • Operating characteristics:

A picture window has no operating characteristics because it does not open.

  • Size Considerations:

A picture window is designed to as narrow as possible so, compared to a fixed casement, it doesn’t have the same level of structure. Extremely large windows may be more appropriate as fixed casements and not pictures.

  • Design issues:

The reason it is called a ‘picture’ is because it maximizes the glass to framing material ratio. Generally, a picture window is used in combinations with horizontal or vertically sliding windows, or on its own. It may be used in a situation where grills will not line up anyway, or there are no grills involved.

  • Energy usage considerations:

Picture windows are excellent in limiting air infiltration, which is a factor in energy usage. GEM picture windows are designed to handle the 1 3/8” thick triple glass which can allow for up to an R9 center of glass. Energy efficiency and a very high Energy Rating are facts with a picture window. You may see a picture window with a better Energy rating (E.R.) than a fixed casement. This is due to the slimmer lines of a picture window allowing for more sunlight to enter through the window. More sunlight means a higher solar heat gain coefficient (SHGC). Solar heat gain does not impact on thermal efficiency, so it doesn’t improve the U (or R) value of a window, but it is part of the formula for an E.R. This can be somewhat misleading, particularly when you think you’re buying an energy efficient window and you may not want the solar heat part of the E.R.’s energy efficiency. This is a perfect segue into our next topic.

  • Allowable sunlight:

With no center barriers and minimal framing, picture windows allow the maximum amount of light of any window style.

  • Structural issues:

What is structural performance? It is the ability of a window to resist bowing or breaking under intense window pressure. A window with poor structural performance, when under pressure, will deflect to the point where it may allow excessive air leakage or water penetration. Picture windows do not have a lot of inherent structure and rely on a quality installation.

Double Hung Windows

  • Operating characteristics:

Inside the frame, there are two sashes. One over the other, one in an ‘inside’ track and one in an ‘outside’ track. They overlap at what is called a ‘meeting rail’. The two sashes both slide up and down. Locks at the meeting rail can be engaged and that prevents either sash from moving, preventing entry.

Many double hung windows have a tilt mechanism built into each sash to allow the exterior surface of the glass to be cleaned from inside the home.

Double hung sashes require a counter weight system, known as a balance, so that no matter where in the track the sash is resting it will be in stasis and neither rise up or fall on its own.

  • Size Considerations:

Like a casement, the ideal shape of a double hung meets the Ionian ideal ratio of a width of 1 with a height of 1.6. (Of course, this is the ideal and reality will vary.) Double hungs can be significantly wider and taller than a casement as only half the windows glass is in each sash and nothing projects out of the frame, minimizing the weight factor.

  • Design issues:

There was a point where virtually all operating windows were double, or at least single, hung windows. This is still somewhat true in the USA, but not in Canada. As a result, many homes were designed around the use of double hungs, which allow for greater widths and heights than casement window.

A functional issue that could also be considered a design issue is the fact that by sliding inside the frame of the window and not projecting out, double hungs lend themselves to environments where one doesn’t want to project out onto a patio, where people will walk, or into a row of bushes adjacent to the house.

  • Energy usage considerations:

Double hung windows are not quite as air tight as a casement or awning window.
However, some GEM double hung windows are designed to handle the 1 3/8” thick triple glass which can allow for up to an R9 center of glass.

There are two reasons they are less air tight. The first is the seals. Casements have compression seals but, because double hungs have to slide, the seals can’t be compression, so they’re not as tight. The second reason is the meeting rail where the upper and lower sash overlap is a weakness, particularly in the corners. However, given that in many modern houses lack of air circulation is a bigger problem than a small amount of air exchange, unless the air leakage has a dramatic effect in regard to local condensation, it is a technical issue, but not a real concern.

  • Allowable sunlight:

Like other sliders, double hungs tend to have high solar gain and let in more sunlight because the framing materials tend to be narrower than in a casement. This is generally true, even adding in the meeting rail to the sashes.

  • Structural issues:

What is structural performance? It is the ability of a window to resist bowing or breaking under intense window pressure. A window with poor structural performance, when under pressure, will deflect to the point where it may allow excessive air leakage or water penetration. Double hungs, by design, cannot be as structurally strong as a casement or an awning. A casement sash is on the exterior of the frame and a strong window pushes it against the frame. Double hung sashes are inside the frame and a strong window is pushing them away from the frame. Additionally, the meeting rail area is susceptible to buckling under strong winds. That being said, these ‘strong windows’ are not anything you would experience in a normal situation. But, this is why the use of double hungs is discouraged in taller structures or exposed locations overlooking cliffs, where high winds are common.

Double Slider Windows – Lift Out or Tilt

  • Operating characteristics:

Inside the frame, there are two sashes. They are side by side with each other, one in an ‘inside’ track and one in an ‘outside’ track. They overlap at what is called a ‘meeting rail’. The two sashes both slide side to side. Locks at the meeting rail can be engaged and that prevents either sash from moving, preventing entry.

Many double sliding windows have a tilt mechanism built into each sash to allow the exterior surface of the glass to be cleaned from inside the home. Those that do not have a tilt mechanism can be lifted out of the frame completely for cleaning the exterior glass.

Tilt sliders sashes require a breaking mechanism on the tilt mechanism to keep the sash from falling out of the frame when tilted.

  • Size Considerations:

The ideal shape of a double slider meets the horizontal Ionian ideal ratio of a width of 1.6 width with a height of 1. (Of course, this is the ideal and reality will vary.) Double sliders can be significantly wider and taller than other operating windows, making them very cost efficient for large windows where, to achieve the same size, one would have to put two windows together in an opening.

  • Design issues:

The truth is, horizontal sliders don’t have the classy looks of more vertical windows, such as casements and double or single hung windows. The best part about double sliders is they offer large glass areas.

A functional issue that could also be considered a design issue is the fact that by sliding inside the frame of the window and not projecting out, double sliders lend themselves to environments where one doesn’t want to project out onto a patio, where people will walk, or into a row of bushes adjacent to the house.

  • Energy usage considerations:

Double slider windows are not quite as air tight as a casement or awning window.
However, some GEM double slider windows are designed to handle the 1 3/8” thick triple glass which can allow for up to an R9 center of glass.

There are two reasons they are less air tight. The first is the seals. Casements have compression seals but, because double sliders have to slide, the seals can’t be compression, so they’re not as tight. The second reason is the meeting rail where the inner and outer sash overlap is a weakness, particularly in the corners. However, given that in many modern houses lack of air circulation is a bigger problem than a small amount of air exchange, unless the air leakage has a dramatic effect in regard to local condensation, it is a technical issue, but not a real concern.

  • Allowable sunlight:

Like other sliders, double sliders tend to have high solar gain and let in more sunlight because the framing materials tend to be narrower than in a casement. This is generally true, even adding in the meeting rail to the sashes.

  • Structural issues:

What is structural performance? It is the ability of a window to resist bowing or breaking under intense window pressure. A window with poor structural performance, when under pressure, will deflect to the point where it may allow excessive air leakage or water penetration. Double sliders, by design, cannot be as structurally strong as a casement or an awning. A casement sash is on the exterior of the frame and a strong window pushes it against the frame. Double slider sashes are inside the frame and a strong window is pushing them away from the frame. Additionally, the meeting rail area is susceptible to buckling under strong winds. That being said, these ‘strong windows’ are not anything you would experience in a normal situation. But, this is why the use of double slider is discouraged in taller structures or exposed locations overlooking cliffs, where high winds are common.

Another factor with horizontal sliders is that of all windows, particularly the tilt versions, horizontal sliders often have the least resistance to water penetration. This is because the requirement for a low sill for tilting action offers very little water retention in the frame.

Single Hung Windows

  • Operating characteristics:

Inside the frame, there is one sash in the bottom half and the top half is a fixed window that looks like a second sash. The operating sash is on an ‘inside’ track and fixed window on an ‘outside’ track. They overlap at what is called a ‘meeting rail’. The lower sash slides up and down. Locks at the meeting rail can be engaged and that prevents the sash from moving, preventing entry.

Many single hung windows have a tilt mechanism built into the sash to allow the exterior surface of the glass to be cleaned from inside the home. To clean the glass on the fixed portion of the window, the lower sash is tilted in, the screen removed and one reaches through the opening and upward to clean the glass.

The single hung sash requires a counter weight system, known as a balance, so that no matter where in the track the sash is resting it will be in stasis and neither rise up or fall on its own.

  • Size Considerations:

Like a casement, the ideal shape of a single hung meets the Ionian ideal ratio of a width of 1 with a height of 1.6. (Of course, this is the ideal and reality will vary.) Single hungs can be significantly wider and taller than a casement as only half the windows glass is in each sash and nothing projects out of the frame, minimizing the weight factor. They can also be larger than double hungs because there is more natural rigidity created by the fixed portion of the window.

  • Design issues:

There was a point where virtually all operating windows were double, or at least single, hung windows. This is still somewhat true in the USA, but not in Canada. As a result, many homes were designed around the use of double or single hungs, which allow for greater widths and heights than casement window.

A functional issue that could also be considered a design issue is the fact that by sliding inside the frame of the window and not projecting out, single hungs lend themselves to environments where one doesn’t want to project out onto a patio, where people will walk, or into a row of bushes adjacent to the house.

  • Energy usage considerations:

Single hung windows are tighter than double hungs, but are not quite as air tight as a casement or awning window. However, some GEM single hung windows are designed to handle the 1 3/8” thick triple glass which can allow for up to an R9 center of glass.

There are two reasons they are less air tight. The first is the seals. Casements have compression seals but, because single hungs have to slide, the seals can’t be compression, so they’re not as tight. The second reason is the meeting rail where the upper and lower sash overlap is a weakness, particularly in the corners. The reason they are tighter than double hungs is they have about half the crack length (location of seals between a sash and frame) because of the fixed portion. However, given that many modern houses lack of air circulation that is a bigger problem than a small amount of air exchange. Unless the air leakage has a dramatic effect in regard to local condensation, it is a technical issue, but not a real concern.

  • Allowable sunlight:

Like other sliders, single hungs tend to have high solar gain and let in more sunlight because the framing materials tend to be narrower than in a casement. This is generally true, even adding in the meeting rail to the sashes.

  • Structural issues:

What is structural performance? It is the ability of a window to resist bowing or breaking under intense window pressure. A window with poor structural performance, when under pressure, will deflect to the point where it may allow excessive air leakage or water penetration. Single hungs, by design, cannot be as structurally strong as a casement or an awning. A casement sash is on the exterior of the frame and a strong window pushes it against the frame. The single hung sash is inside the frame and a strong window is pushing it away from the frame. Single hungs are structurally more secure than double hungs because the upper half, being fixed, in the frame, has more resistance to pressure. Additionally, the meeting rail area is susceptible to buckling under strong winds. That being said, these ‘strong windows’ are not anything you would experience in a normal situation. But, this is why the use of single hungs is discouraged in taller structures or exposed locations overlooking cliffs, where high winds are common. If the choice in one of these locations is a single hung or double hung, a single hung has a better rating and a better chance of performing to an acceptable standard.

Single Slider Windows – Lift out and Tilt

  • Operating characteristics:

Inside the frame, there is one operating sash in the inner track area which can either be on the left or the right. Normally it is on the left from the outside. The other side is a fixed window that looks like a second sash. They overlap at what is called a ‘meeting rail’. The inner operating sash slides sideways. Locks at the meeting rail can be engaged and that prevents the sash from moving, preventing entry.

Many single tilt slider windows have a tilt mechanism built into the sash to allow the exterior surface of the glass to be cleaned from inside the home. Lift out sliders have an operating sash that can be completely removed from the frame for cleaning. To clean the glass on the fixed portion of the window, the lower sash is slid over, the screen removed, and one reaches through the opening and sideways to clean the glass.

  • Size Considerations:

The ideal shape of a single slider meets the Ionian ideal ratio of a width of 1.6 with a height of 1. (Of course, this is the ideal and reality will vary.) Single sliders can be significantly wider and taller than most other windows as only half the windows glass is in each sash and nothing projects out of the frame, minimizing the weight factor. They can also be larger than double sliders because there is more natural rigidity created by the fixed portion of the window.

  • Design issues:

There was a point where virtually all operating windows in modest priced new construction for the side and back of the home were double, or at least single sliding windows. As a result, many homes were designed around the use of double or single sliders, which allow for greater widths and heights than casement window. This often makes replacing a horizontal sliding window with another horizontal sliding window the least costly option, although it is rarely considered to be the best option for energy savings or functionality.

A functional issue that could also be considered a design issue is the fact that by sliding inside the frame of the window and not projecting out, single sliders lend themselves to environments where one doesn’t want to project out onto a patio, where people will walk, or into a row of bushes adjacent to the house.

  • Energy usage considerations:

Single slider windows are tighter than double sliders, but that is not saying a lot!
Next to double sliders they are generally the weakest for resisting air and water penetration. From an energy point of view, some GEM single hung windows are designed to handle the 1 3/8” thick triple glass which can allow for up to an R9 center of glass.

There are two reasons they are less air tight than, for example, a casement. The first is the seals. Casements have compression seals but, because single sliders have to slide, the seals can’t be compression, so they’re not as tight. The second reason is the meeting rail where the sash overlaps the frame is a weakness, particularly in the corners. The reason they are tighter than double sliders is they have about half the crack length (location of seals between a sash and frame) because of the fixed portion. However, many modern houses lack of air circulation and that is a bigger problem than a small amount of air exchange, unless the air leakage has a dramatic effect in regard to local condensation, it is a technical issue, but not a real concern.

  • Allowable sunlight:

Like other sliders, single sliders tend to have high solar gain and let in more sunlight because the framing materials tend to be narrower than in a casement. This is generally true, even adding in the meeting rail to the sashes.

  • Structural issues:

What is structural performance? It is the ability of a window to resist bowing or breaking under intense window pressure. A window with poor structural performance, when under pressure, will deflect to the point where it may allow excessive air leakage or water penetration. Single sliders, by design, cannot be as structurally strong as a casement or an awning.

A casement sash is on the exterior of the frame and a strong window pushes it against the frame. The single slider sash is inside the frame and a strong window is pushing it away from the frame. Single tilt sliders are significantly weaker in resisting deflection than a lift out. Lift outs have a lower rail that covers a part of the sash sill to resist deflection. By design, a tilt slider cannot have this benefit.

Single sliders are structurally more secure than double sliders because the outer glass, being fixed, in the frame, has more resistance to pressure. Additionally, the meeting rail area is susceptible to buckling under strong winds. That being said, these ‘strong windows’ are not anything you would experience in a normal situation. But, this is one reason why the use of single sliders is discouraged in taller structures or exposed locations overlooking cliffs, where high winds are common. If the choice in one of these locations is a single slider or an awning, the awning has a better rating and a better chance of performing to an acceptable standard.

Tilt and Turn Windows

  • Operating characteristics:

Inside the frame, there is one operating sash which opens inward. The sash overlaps the frame. This type of product can be used as both a window or a door. When used as a door, the sill of the product can be lower. These windows have a heavy-duty hardware and often can have two different ventilation functions. They can swing in like an inswing door or they can open inward at the top like a hopper window. (Note that the operations are one or the other and care needs to be taken to not get caught half way with both.)

  • Size Considerations:

The ideal shape of a Tilt and Turn is the Ionian ideal ratio of a width of 1 with a height of 1.6. (Of course, this is the ideal and reality will vary.) Because of the strength of the hardware, these products can achieve relatively large sizes, which is why they can be used as doors.

  • Design issues:

As an inward opening window, Tilt and Turn windows are a challenge for use with blinds and curtains. Screens need to be external. Use of blinds inside the sealed unit is a possibility. Curtains that when open are beyond the frame of the window will work, but not provide privacy when the window is open.

  • Energy usage considerations:

Tilt and Turn windows are among the tightest windows available. Like a casement, they close into compression seals, but, because the sash overlaps the frame there is an additional barrier to air infiltration. Frames will tend to have better U values. If solar gain is desirable, the bulk of the framing materials will reduce available solar heat more than a casement or awning.

  • Allowable sunlight:

As noted, Tilt and Turn windows, particularly in smaller sizes, tend to have reduced glass to vinyl ratios and allow less sunlight and solar heat gain.

  • Structural issues:

What is structural performance? It is the ability of a window to resist bowing or breaking under intense window pressure. A window with poor structural performance, when under pressure, will deflect to the point where it may allow excessive air leakage or water penetration. By design, a Tilt and Turn window is built to resist deflection and will have excellent structural ratings and water penetration resistance when compared to other operating windows.

Hopper Windows

  • Operating characteristics:

Hopper window are hinged at the sill and open inward at the top for ventilation. Usually a limit of some nature (a bar or a chain) is used to only allow the sash to come down part way and not rest on the sill and wall.

  • Size Considerations:

The ideal shape of a Tilt and Turn is the Ionian ideal ratio of a width of 1.6 with a height of 1. (Of course, this is the ideal and reality will vary.) Hopper windows do not tend to be particularly structural and are mostly useful in smaller openings, particularly as basement windows.

  • Design issues:

As an inward opening window, Hopper windows are a challenge for use with blinds and curtains. Screens need to be external. Use of blinds inside the sealed unit depends on the availability of sealed units wide enough for the blinds. Curtains that when open are beyond the frame of the window will work, but not provide privacy when the window is open.

  • Energy usage considerations:

The choice of a hopper tends to be determined by specific opening limitations and they are used in these situations in spite of limited resistance to air penetration compared to most other operating windows. Sash and frame materials will be similar as sliding systems in regard to U value through framing materials.

  • Allowable sunlight:

Hoppers have an excellent glass to vinyl ratio for high solar heat gain, however as basement windows their exposure to sunlight is limited at best.

  • Structural issues:

What is structural performance? It is the ability of a window to resist bowing or breaking under intense window pressure. A window with poor structural performance, when under pressure, will deflect to the point where it may allow excessive air leakage or water penetration. A hopper window sash has limited resistance to pressure as a result of opening inward. It should not be used in situations where structural performance requirements are high.

Combination Windows – Bay and Bows

  • Operating characteristics:

Bays and bows are projecting windows, made up of combinations of single window styles. Generally, the are combinations of vertical operating windows (casements, single hungs or double hungs) with fixed or picture windows. Because the project outward from the plane of the wall, they require a roof structure as well as a sill structure to fill the gap from the wall plane to the window, as well as provide structural support for the windows which are now ‘hanging in space’.
Regarding the roof structure, if the entire projection is within an eave of the home, it is common for the bay or bow to simply have a structure that goes straight up in the existing eave. When no eave exists, a roof with its own water-repellant capacity is required. Common roofs have the same shingles as the rest of the house or sometimes a metal roof.

  • Size Considerations:

Bay and bows can fill relatively large openings. A limitation is the ability of the house structure to support the weight of the projecting window. In some cases, and under-structure may be used to support the projecting window.

  • Design issues:

Bays and bows require special couplers to create the angles. There are a limited number available. This results in not being able to be totally customized regarding the relationship between width and projection. Bays and bows can be an excellent location for in home plants.

  • Energy usage considerations:

Beyond the energy usage of the individual windows, the space created outside the wall plane often has comfort issues as it does not benefit from the heat in the room as much as space inside the plane of the wall. In some cases, effort may need to be made to redirect heat sources to keep the bay area warmer. Use of insulated seats and heads in the projecting window helps to offset this.

  • Allowable sunlight:

Bays and bows are excellent sources of sunlight as the opening faces multiple directions.

  • Structural issues:

What is structural performance? It is the ability of a window to resist bowing or breaking under intense window pressure. A window with poor structural performance, when under pressure, will deflect to the point where it may allow excessive air leakage or water penetration. Bay and bow windows have significant requirements for structure because they are projecting outside the plane of the building envelope. There are cable systems specifically designed to use the header structure of the house to carry the weight of the combination unit.

Skylights and Roof Windows

  • Operating characteristics:

Skylights are fixed windows in a roof area. Roof windows are operating units, generally opening like an awning on a roof. The roof can be sloped or flat.

  • Size Considerations:

Installing a skylight or roof window that is wider that the joists requires significant and important structural work to prevent structural problems with the roof. This significantly limits the widths that can be used.

  • Design issues:

Skylights and roof windows can add significantly to light and ventilation

  • Energy usage considerations:

In the summer, roof windows can help vent unwanted heat. Constant, direct exposure to sunlight can be an excellent source of free solar heat in winter.

  • Allowable sunlight:

Skylights and roof windows are excellent sources of sunlight for spaces such as attics and rooms directly below the roof where options for wall mounted windows is limited.

  • Structural issues:

What is structural performance? It is the ability of a window to resist bowing or breaking under intense window pressure. A window with poor structural performance, when under pressure, will deflect to the point where it may allow excessive air leakage or water penetration. Skylights and roof windows exposure to the elements means they will require more maintenance than other windows. Failure to maintain them can easily result in water leakage.

More than any other window except, perhaps, a bay or bow, a roof window installation should always be left to a professional as changing a roof line is a significant structural change. Properly integrating the window into the water management system of the roof is critical.