Beyond Windows – Designing with Large- Format Glazing  

Glass and glazing are integral to all residential designs with punched or mulled windows being the most commonly used product (i.e., awnings, casements, double-hung). In this course we look beyond these well-known choices and focus on a full range of available large-format glazing systems. Such systems include fixed glazing (i.e., picture windows), fully glazed doors (swinging, sliding, multi-slide, lift slide), large bi-fold doors, and residential curtain wall systems. All of these can be used to create contemporary or traditional residential buildings that are dramatic, inviting, flexible, and very livable. At the same time, it is possible to specify any of these systems to meet a variety of performance needs based on the details of the framing, sealing, and glazing selected. These include thermal and air infiltration control to meet high-performance energy standards such as Passive House. They can also be specified to meet the demands of particular projects related to storm resistance/resilience or building material needs such as copper or bronze cladding on glazing systems. Understanding the full range of options and capabilities allows architects the opportunity to create residential designs that are delightful to live in, comfortably energy conserving, and operationally durable.

Photo: CLB Architects; Kevin Scott Photography; courtesy of Loewen Windows and Doors

Architects have many choices in selecting glazing and fenestration products to incorporate into residential designs to create inviting spaces that also perform well.

GLAZING OVERVIEW

Manufactured glazing products used in residential design are typically made from identifiable parts by any one of many different glazing product manufacturers. Of course, not all manufacturers provide the same type or style of products. Some have the capabilities to provide higher performance products than others. Certain manufacturers are also equipped to provide unique or innovative products when called for. With so many choices available, it is incumbent on the design professional to discern which products are best suited to a particular project both to meet the design intent as well as the performance requirements.

Design Options

Regardless of the manufacturer or the type of product, there are a few fundamental design aspects and options for all glazing products. Often, selecting from these aspects is influenced by the project design intent, the location, or performance requirements to meet codes or other standards. Some of the common options include the following:

• Glazing: There are fundamental choices in the type of glass used such as float/ annealed, tempered, heat strengthened, or laminated. There are also processes that affect the characteristics of the glass such as coatings, color tints, etc. The most commonly specified coating is for low emissivity (Low-E). This process helps control the flow of radiant heat through the glazing to enhance the energy performance of a building. It may change the color of the glass slightly, but not enough to be a deterrent to using it. Further, there are fabrication options such as creating double-glazed insulated glazing units (IGUs). Triple glazing is increasingly being asked for in colder climates causing certain fabricators and manufacturers to respond with product offerings to meet that demand. Determining which glass options are best suited to a project is usually an iterative process that balances the look, size, location, and performance of the glass with the other components of a glazing product.
• Frame and Sash Materials: The glass is mounted into a sash that surrounds it on all four sides. That sash is set into a frame which is the intermediary between the glazed sash and the building. There are choices in the material for these items including wood, aluminum, fiberglass, vinyl, or others, each with its own design and performance characteristics, advantages, and disadvantages. Different fenestration products may be offered in different materials by different manufacturers including different species of wood (i.e., Douglas fir, white oak, mahogany, etc.). Some woods are denser and longer lasting than others and also provide different appearances and colorations. Check with manufacturers for their standard and optional offerings.
• Prefinished Options and Colors: Different manufacturers offer different ranges of finish options for the frame and sash materials. White and dark bronze are common for vinyl and aluminum but there may be other options available too such as greys, greens, tans, and red. Wood products may be unfinished or prefinished in a full array of popular stain colors. Some finishing may include distressing of the wood for a more natural look. If a particular finish is being sought, however, don’t assume that all manufacturers have it available. It is best to check first.
• Hardware: The hardware for operable fenestration products is similarly varied by manufacturer. While the functionality of the hardware is essentially the same between one manufacturer and another, the style, color, and finish of that hardware can vary considerably. Some offer multi-point locking hardware on selected products which provides a greater degree of security. There are also European-style hardware latches and locks that may be available which are typically more robust and durable while still offering an elegant appearance.
• Enhancements: Some projects may require certain enhancements to a glazing product. For example, some can be wind-strengthened for greater wind and storm resistance where needed. Other products can be covered with more durable cladding or coatings such as non-ferrous metals like bronze or copper.
• Custom Capabilities: Some manufacturers provide their standard products and that is all. Others can readily customize the size or shape of their products as long as it remains within certain limits of their fabrication capabilities. Certain product manufacturers can offer a wide range of custom capabilities and should be consulted during the project design process to see what is readily possible.

While the variability of choices and options gives designers a lot of freedom to work with, the standardized nature of the manufacturing allows for a good degree of predictability on performance.

Photo: Narofsky Architecture; Phillip Ennis Photography; courtesy of Loewen Windows and Doors

Glazed fenestration products are available with a range of interior and exterior materials, glass types, hardware, and other features.

Performance Testing

Windows and other glazed products need to perform well in terms of their inherent structural integrity as a product, their ability to withstand weather of all sorts, and their energy-related characteristics. In order to independently determine the true performance of glazing products, there are several national testing and functionality standards that help with quality assurance. These include the following:

• Building Codes: Across all 50 of the United States, and in many countries around the world, model building codes have been adopted that are developed by the International Code Council (ICC). Referred to as the International Codes or I-Codes, they include a coordinated family of building safety codes such as the International Building Code (IBC), the International Residential Code (IRC), the International Energy Conservation Code (IECC), and 12 other specialty codes. These codes provide the minimum acceptable performance for buildings and the products used in them. In the case of residential fenestration products, The IRC and the residential portion of IECC are the most relevant in that they identify the prescriptive and performance requirements that such products need to meet when used in buildings. This includes updates that encourage or even require higher-performing triple glazing instead of just double glazing in colder climate zones.
• National Fenestration Rating Council (NFRC): Perhaps the best-known and most widely used standard for residential glazing products is done by the independent National Fenestration Rating Council (NFRC). The certified results of their testing are used to show compliance with codes including the IRC and the IECC with a label attesting to the results affixed to a tested product by the manufacturer showing its overall and specific performance characteristics. The NFRC recognizes that window performance is not limited to any single criterion. Rather, there are a number of factors that need to be looked at, tested, and assessed to determine the true overall performance of a window.

U-factors (the inverse of an R-value) are usually what come to mind first, which measure the rate at which a material or product transfers heat through it. When observing U-factors, it is important to differentiate U-factor variables for the insulated glass alone (e.g., ‘center-of-glass’ U) or for the window unit as a whole. NFRC utilizes the component modeling approach to calculate the whole U-factor of a window by assessing the glass, the spacer between the glass, the sash, and the frame. Of course, the size and make-up of the glass are also important - including the number of panes that make up insulated glazing units (IGUs). Ultimately, the total NFRC U-factors for windows are based on actual testing of representative manufactured units and expressed in normal fashion as a decimal value with a lower number showing less heat transfer, therefore greater energy efficiency. Ratings generally fall between 0.20 and 1.20.

The second notable factor in the energy efficiency performance of a window is the rate of air infiltration, particularly in operable windows. The International Energy Conservation Code (IECC) sets the bar at 0.20 cubic feet per minute per square foot of window as the maximum allowable air leakage rate for windows with some exceptions allowing 0.30 cfm/square foot. This is the same rate as for sliding and swing doors in commercial construction. The NFRC takes air infiltration into account when testing window units, so manufacturers pay attention to details of construction in this regard too. Proper weather sealing and tightness of fit all come into play but so does the type of window or glazed product.

Another aspect of the glass used in tested products that affects the energy performance is its solar heat gain coefficient (SHGC). This metric indicates how much solar heat passes through the glass compared to what is reflected away. The SHGC rating is expressed as a number between 0 and 1. The lower the SHGC the less solar heat is transmitted through the glass and the cooler a residence will be. In building situations where heating from passive solar gains is desired, then a high SHGC is desirable to take advantage of the free solar heat. In other situations where cooling is the primary energy driver in a building, then a lower SHGC is needed to prevent unnecessary air conditioning use.

The visible transmittance of light (VT) is the final factor which is expressed as a number between 0 and 1. The higher the VT the more visible light is transmitted through the glass. Treatments for some of the energy efficiency characteristics of glass can interfere with the ability of people to see clearly through it. Hence the VT is useful to help identify acceptable levels of clarity for views or the use of natural daylighting in buildings.

• American Architectural Manufacturer's Association (AAMA): This independent testing agency is most often used for large-format glass and fenestration products in both residential and commercial buildings. An AAMA Window Certification requires three tests: 1.) Air Leakage- Windows with a tested air infiltration rate above 0.30 cfm at 25 mph fails; below that threshold, it passes. The lower the number the less air infiltration into a building. 2.) Water Leakage- windows are subjected to 8 inches of rain per hour and increasing wind loads until water leaks through the window. The minimum standard to pass is 33 mph wind in simulated rain conditions. 3.) Structural Strength- increasing wind is blown against the glazing product until it breaks. The minimum standard that a product must withstand is 94 mph.

Windows and other products that meet the requirements of all three tests are declared AAMA Certified Windows with an affixed label located inside the head of the frame. AAMA Gold Label Certified Windows designates that the tested product has passed both AAMA and NFRC testing standards.

• Enhanced Performance Standards: Many design professionals are interested in creating buildings that exceed the minimum requirements and go beyond, excelling in the areas of energy performance or durability in particular. In that regard, there are several standards to identify the degree of performance achieved.

Related to energy, the ENERGY STAR program administered by the US Department of Energy tests and rates window units, specifically to determine if they perform high enough above minimum standards to earn the ENERGY STAR label. The ENERGY STAR program does not conduct tests, rather it uses NFRC overall window thermal test results and assigns minimum criteria for each of the recognized geographical climate zones in the United States. Typically, ENERGY STAR ratings require at least 20 percent better performance than code minimum requirements. It does not consider AAMA Air, Water, and Structural test results.

The LEED Green Building Rating program is perhaps the best-known program for improving the energy performance and general sustainability of residential and commercial buildings. Windows and glazed fenestration products are not specifically identified with prescriptive performance requirements under LEED, but they play a key role in addressing overall energy use, daylight, and views – all of which are areas that have the potential to earn points toward LEED certification.

Another program growing in popularity is Passive House which is a voluntary standard resulting in ultra-low energy buildings requiring very little energy for space heating or cooling. In order to achieve that goal, all aspects of the thermal envelope are addressed including all fenestration. Typically, that means additional requirements on the windows or other glazed products for reduced heat transfer and air infiltration. In order to meet those requirements, manufacturers need to have the capability to produce very high-quality products.

In cases where a residence is subjected to potential extreme weather conditions, such as along a coast, structurally enhanced products are available that exceed the International Residential Code, the Florida Building Code, and other coastal standard requirements, such as the stringent Dade County certification. Such products are designed to endure hurricanes, tropical storms, high winds, driving rain, excessive heat, and even exceptional freezing conditions. These conditions are met through additional product engineering as well as including impact-resistant glazing. Wind-borne debris becomes a major concern during windstorms and hurricanes. To protect the integrity and interior of homes, windows, and doors must resist penetration and remain in place and intact when struck by this debris. Impact-designed laminated-glass windows and doors pass windborne debris impact tests. Even when broken, glass fragments remain attached to a composite interlayer between the laminations thus preserving the integrity of the building envelope during a storm. Many such glazing impact-resistant products are D-Missile certified meaning that they are tested to withstand impact from a 9-pound 2 x 4 stud, eight feet in length, at an impact speed of 50 feet per second. Products are then tested to withstand 9,000 positive and negative wind loading cycles without failure.

Photo: Nordlys Lodging - SALA Architects; Corey Gaffer Photography (left) Coastal Maine - Royer Architects; Meredith Brockington Photography (right); both courtesy of Loewen Windows and Doors

Windows and other glazing products can be specified to meet the demands of severe weather conditions in all climate zones.

Limitations

While everyone likes to think that anything is possible for glazed fenestration products, the reality is that there are some manufacturing and shipping limitations that need to be taken into account during design, especially for larger-sized units. These include the following factors:

• Glass Weight: Sometimes, heavier laminated glass is called for either to address security or resiliency concerns. Heavier glass means larger support members for the sash and frames. While that makes the products more robust and inherently stronger, it also means that they need to be properly integrated with the building construction in terms of depths, thicknesses, and sealing of edges, seams, etc.
• Preassembled Size: Many windows and other products can be combined together (i.e., “mulled”) or fabricated as a larger set of panels. However, there are practical limits on how large is too large to handle effectively in the field or to ship over the road. As a general rule, units up to 9 feet tall can be mulled together but the weight will be the limiting factor for what is practical to handle and install.
• Uniform Appearance: Many facade designs will incorporate different-sized fenestration products not only around a building but across the same wall. That would suggest that different thicknesses of glass or sashes are possible and may be considered. However, doing so can create some real design issues. First, the appearance of the different products can look notably different both along the exterior facade and the interior wall due to different sized sash and frames. Second, different thicknesses of glass can produce different visual clarity and visible light transmission when looking through them from inside the building. The best practice is to default to having all of the glazing components match the thickest or strongest product needed along a wall, if not the whole building.

Ultimately it is up to the manufacturer to provide all of the details about these different product characteristics and capabilities. Then it is the architect or designer’s role to select the products that best suit the design and performance needs of a project. With all of this in mind, we take a closer look at common options for standard and oversized glazing products in the following sections. Keep in mind that there are many different types of glazing products beyond standard windows, although those are touched on too. Many large or oversized products have become popular for design reasons and in response to owner requests. All of the products discussed need to meet performance requirements which can vary depending on location, owner requirements, or building type.

Photo: Horizon House – Lake Flato Architects; Casey Dunn Photography; courtesy of Loewen Windows and Doors

Awning windows are hinged at the top and allow for ventilation in the same manner as casement windows. They can be styled to suit either traditional or contemporary designs.

PUNCHED OPENING WINDOWS

Perhaps the most commonly used type of fenestration in residential buildings is “punched openings.” This term refers to the appearance of an opening being punched into the wall as a distinct opening. Typically, they are placed into the exterior structural walls and are the usual reference point for all other types of glazed products. These products are designed, installed, and purchased as distinct units in a variety of types and styles. They are commonly available in standard sizing patterns with custom sizing choices available in many cases. Manufacturers can usually accommodate different types of glass including double or triple glazing in some instances. The performance of punched windows varies based on their design and operation which are discussed further as follows:

Operable Windows

Most residential designs default to operable windows of one type or another since they provide the code-required natural ventilation in addition to daylight. The design appearance of operable windows can be selected from standard offerings in traditional or contemporary styles along with all of the general glazing design options discussed earlier. Operable windows can be equipped with insect screening as an add-on component. Some manufacturers also offer fully retractable screening which provides full visual clarity when the screen is coiled into a portion of the window frame. It operates by sliding along a track to cover the opening allowing the window to be open and protected from insects and then return to its concealed position when no longer needed.

One traditional window operation type is double or single-hung windows that slide vertically in a track. Double-hung windows allow both of the two sashes to move, while single-hung windows incorporate one fixed and one moving sash. Air infiltration control needs to be addressed on any movable sashes particularly where two movable sashes meet along their stiles since a tight seal is needed to keep out drafts. The particular appearance of single- and double-hung windows can vary depending on the manufacturer’s offerings with options for traditional, craftsman, or more contemporary design languages incorporated.

For building designs that seek a more contemporary look using a single operable sash in each window, then awning and casement style windows are appropriate. Casement-style windows are usually intended for a vertical orientation with the hinge on one side and the operational hardware on the bottom. Awning windows use the same components, just in a horizontal orientation with the hinge at the top and the hardware on the side or the bottom. The quality and appearance of awning and casement windows can vary by manufacturer, particularly in regard to the hardware that makes them operate, so it is advisable to review specific product details. The two common types of operational hardware are “push-out” systems (allowing the sash to be literally pushed outward) and a rotating handle (cranking the sash outward). Regardless, all casement and awning-style windows close and lock tightly against a weather seal around the entire perimeter of the single sash. This means they can usually provide better air infiltration control when compared to double-hung windows. The locking hardware is usually concealed in the frame and closes against the sash at multiple points.

Photo: Steve Wisenbaker Architects | Kasten Builders | Paul Dyer Photography; courtesy of Loewen Windows and Doors

Fixed glass or picture windows can be designed into custom sizes and shapes to provide daylight and views in conjunction with separate operable windows for ventilation.

Fixed Windows

Some building designs seek to maximize views and daylight while minimizing air infiltration. As long as there is enough natural or mechanical ventilation, then the use of fixed, picture, or direct set windows is an appropriate solution. They are usually available with the same sash and frame appearances and details to match the operable windows for a consistent look across a building facade.

One benefit of fixed windows is that they have the potential to be sized larger than operable windows depending on the window frame and sash details. There are limits based on the maximum practical area or code requirements for the glass too, but generally, a wide range of sizes and shapes can be considered. The style may allow for a minimal frame to create a clean aesthetic or for stylized frames and trim to match the overall design intent of the building. They also have the potential for very good energy performance by selecting high-performance glass, triple glazing, or other treatments.

In terms of coordinating large or oversized fixed windows with the rest of the building construction, it is worth noting that exterior-glazed products provide an easier on-site installation into wood framed walls. The alternative would be to install fixed glass into a site-built frame, from the interior, which would typically involve more time and effort. For high-performance buildings, some fixed windows can also work with “rain screen” principles which allow for water deflection and drainage behind the cladding.

RESIDENTIAL GLAZED CURTAIN WALL

Residential curtain walls are a more complete approach to fixed glass across a large wall area. Such systems can be fabricated from a variety of materials, but one preferred residential approach is to use wood timbers as the supporting frame. This accomplishes several things. First, the wood provides a predictable material to base engineering and support calculations on. Second, it provides the visual appeal of natural wood which is commonly used on the interior side of residential fenestration. Third, the wood material has better thermal performance than the use of an aluminum frame system.

Timber curtain wall (TCW) systems for residential applications are tailored to the specific requirements of each project by a fabricator using parts from a manufacturer. As such, every TCW is treated as a custom design that will go through a detailed shop drawing process to ensure that all the architectural and engineering specifications are met. Residential TCW units can be factory assembled and hand-prepped for improved quality control. Timber connectors, gaskets, and glass carriers can be pre-applied. Completed units are commonly predrilled, marked, and labeled. Each entire timber curtain wall unit is shipped in a knocked-down condition to the site ensuring accurate, easy assembly and field glazing. By comparison, conventional, or stick-built curtain wall systems require each horizontal section to be placed one after the other with a high degree of quality checking and field precision necessary for the installation.

Photo: Steve Wisenbaker Architects | Kasten Builders | Paul Dyer Photography; courtesy of Loewen Windows and Doors

Timber curtain walls provide large-scale glazing for residential buildings with aesthetics, strength, and environmentally friendly aspects all a consideration.

To ensure strength and resistance to warping and twisting, horizontal and vertical timber components should be either glue-laminated solid lumber or engineered core lumber with finished facings. Transoms or horizontal rails are the horizontal members of the curtain wall system. The mullions or vertical members are anchored to wood framing or a concrete slab. These components support the dead weight and wind loads of the curtain wall and transfer those loads to the building structure. The thickness of the timbers is commonly 2" - 2-1/8" with a timber depth of 4" to 9“, although these dimensions will vary based on wind load and structural criteria.

In designing and specifying a TCW system for a residential project, several things need to be kept in mind. First, engineering considerations need to be investigated with careful integration with adjacent elements such as floors, wall claddings, roofs, beams, and other building envelope components. Second, the configuration of the TCW needs to be accounted for since it can be fabricated for vertical wall systems, sloped roof systems, and corner conditions. They can also incorporate any combination of fixed and operable window and door units. Third, heavy gauge extruded aluminum is the most common choice for an exterior cover to the TCW system since it is most likely to retain its shape, resist denting, last longer, and be the most economical. It can be finished in some commonly available techniques including Class I anodic coatings (AAMA 611) or high-performance factory-applied fluoropolymer thermoset coatings (AAMA 2605). These finishes are known for their excellent resistance to weather and environmental degradation.

Glazing options for TCWs include a full variety of glass and coating selections, suitable for different climate zones or environmental concerns. These include monolithic glass, dual and triple-glazed sealed insulating glass units (IGUs), impact-resistant laminated glass, sound-attenuated glass, annealed, and tempered glass. Most glazed units are limited by maximum practical sizes for typical sealed unit glazing, although that will vary based on the glass specification. Larger sizes may be available, but costs and time schedules can increase significantly, so consultation with a manufacturer is advised.

In some residential timber curtain walls, there are no weep holes in the horizontal clad members. Instead, water that strikes a TCW is conducted through the exterior seal and gaskets, to the base/sill where it can percolate and drain out. Water control is determined by the design of the connectors and the integrity of the gasket system. Two or three-level, continuous EPDM gaskets with integrated drainage has become the industry standard.

GLAZED DOOR SYSTEMS

Once a glazing product is large enough to walk through, it is considered a door and may be operable or incorporate fixed panels next to it. The height and width can vary from standard to oversized door dimensions depending on the type of product used. Some of the most preferred door systems are discussed in the following sections.

Swinging Glass Doors

Glazed doors can be incorporated as a single full glass swinging door or combined with others (up to 4 doors in one frame) to create attractive and high-performance glazed openings. The panel thickness of the door can vary depending on the strength needed and the number of layers of glass sought. Common door panel thicknesses are 1 ¾ inches and 2 ¼ inches. The 2 ¼-inch-thick door panels are generally more robust and can accommodate triple glazing more easily. Narrow stile door options are available for some doors as well. These contemporary door panels can have minimal stiles and rails for maximum views.

Photo: RKB Construction Studio; Trejo Photography; courtesy of Loewen Windows and Doors

Swinging glass doors can be used individually or in groupings to create an entry or an overall glazed opening scheme.

Swinging glass doors can be fabricated as aluminum-clad doors or all-wood doors. If they are selected from the same company that produces the other glazing products, then there is a good chance the finishes and appearances will match. The door style can be rectangular, radius-top, or even custom shaped. Configurations include inswing, outswing, right or left-handed, and fixed configurations. Supplemental items such as transoms, side-lites, and screen doors can be readily incorporated to match swinging glass doors.

Bifold Doors

When a transition between indoor and outdoor living is called for in a design, then a large, continuous door opening can be created using bifold glass doors. Essentially bifold doors are made up of multiple door panels that fold open and are stacked on one or both sides of the opening. They are available in configurations of up to 16 panels, which can provide uninterrupted openings of up to 52 feet wide and up to nine or ten feet high. Individual panels can be up to 39 inches wide with custom sizes available. Door panels can fold inward or to the outside so as not to disturb interior furnishings. There is also the option to incorporate a passage swinging door in one section which allows free access without opening the entire set of bifold doors. This is all possible because the weight of the door is typically carried at the head, not the sill, allowing for a smoother transition at the floor.

In terms of options, both wood and aluminum bifold door products are available in a full range of finish colors or wood pre-stains. Wood and metal casings can be provided in some cases as well as optional mid-rails across the panels. Decorative glass work simulated divided lites can be specified where appropriate to a building design. Retractable screens can be added as well to cover the full opening area to maximize ventilation and to protect from insects.

Photo: Hamilton Snowber Architects | Stacy Zarin Goldberg Photography; courtesy of Loewen Windows and Doors

Bi-fold doors create large-scale openings, even in smaller spaces to allow maximum daylight and passage to outdoor areas.

Sliding Patio Doors

A common staple of residential design since the mid-twentieth century has been a sliding patio-style door. They have been popular because they provide a large expanse of glass and access between inside and outside without the problem of door swings interfering with other objects or people. While a two-panel configuration is what most people think of with one sliding operable panel and one fixed, there are other options too. It is common for manufacturers to provide three- and four-panel options with one or two operable panels and the remainder as fixed glass panels. The width of the panels can vary but the common sizes match standard residential door sizes such as 2’-6” or 3’-0”. The panel heights typically match standard door opening heights. This standard dimensioning provides design versatility and significant opportunities for filling a wall with a large opening.

Sliding patio doors typically slide along rollers on the bottom of the door allowing them to open and close readily. Heavy laminated sash construction and tempered safety glass address code and safety concerns. Security is addressed with integral locking hardware and frame construction. Some incorporate an anti-panel-lift device to prevent intrusion as well. Screens can be a sliding screen panel or a retractable screen that rolls up to one side of the door in an enclosed casing.

The design options of sliding patio doors are typical of other standard glazed products in terms of materials, finish, and colors. They can be manufactured in wood, aluminum, or other materials depending on project needs. Hardware is more common to windows than doors in that it is provided with sliding doors as an integral part of the product, subject to variations per different manufacturers. For performance, the full set of choices for glass and frame performance is available. Some manufacturers offer standard 2¼” thick panels for patio doors which allows for a triple-glazed unit, resulting in enhanced energy performance.

Multi-Slide Doors

Multi-slide doors are a cross between sliding patio doors and bifold doors. Their operation is based on sliding panels along a bottom track that may be recessed into the floor in some cases similar to a sliding patio door. Multiple panels can stack out of the way to one or both sides, however, similar to a bifold door system, and create a full-width glazed opening. As such they can create a wider opening than sliding patio doors. They can also be fabricated in taller panels such that they can fill a full eight- or nine-foot wall height with multiple sliding panels.

Photo: Horizon House – Lake Flato Architects; Casey Dunn Photography; courtesy of Loewen Windows and Doors

Multi-slide patio doors offer large-format glazing that can be customized in two-, three-, or four-panel configurations.

As a result of the greater variability in panel sizes, multi-slide doors can provide a cleaner, more elegant design appearance. It also helps that they can incorporate narrower frames around the panels. All of this can help create large, dramatic openings with a fairly seamless transition between indoor and outdoor spaces. The hardware used is different from other types of glass doors to allow smooth operation. Performance can vary based on the manufacturer’s details but at least one provides 2-1/4” thick panels to accommodate triple glazing, add strength, and be more durable than other options.

Due to the larger size and unique nature of multi-slide doors, adding screens deserves some special attention. Sliding screen doors that retract into adjacent jambs is the preferred solution since conventional sliding screens would need to stack and have multiple tracks to accommodate the full width of the opening. The operation of these larger doors can also be made even easier with automated motors and controls and integrated flush handles. Designed to respond to the push of a button, automated multi-slide doors can be operated smoothly yet swiftly while opening and closing. Control is based on either a wireless wall switch or a remote fob that moves the panels as selected. In the event of a power failure, the panels should always still have the capability to be operated manually. Further, automation does not remove the need to physically lock the door for security, which should still be done manually.

Lift-Slide Doors

Some of the largest-sized glass door systems are lift-slide doors. They are based on sill-mounted large panels up to 7 feet wide and 12 feet high allowing for maximum opening size opportunities, although the maximum recommended panel size is 70 square feet of glass. The tracks and hardware in these products are designed to allow the door panels to glide fairly effortlessly by lifting the panels up so they can move freely along the sill track. To close them, they can slide and be lowered to lock down for enhanced weather protection and security. The hardware can also be specified with stainless steel components for corrosion resistance. Thresholds can be selected based on the degree of weather and water resistance required. Flush track options may include integral drainage, creating a safer and seamless transition between interior and exterior spaces.

Photos: Salt Architecture | Dan Cutrona Photography; courtesy of Loewen Windows and Doors

Lift slide doors are among the largest available and offer opportunities for dramatic glazed openings and connections to the outdoors.

The typically high structural integrity of these products combined with different threshold options allow lift-slide doors to be located in areas of high wind and weather exposure where homeowners desire expansive views such as mountains, hillsides, coastlines, or lakefront vistas. Thermal performance can be comparable to other large-format glazing products depending on the materials selected. Dual, triple, and impact glazing are available to accommodate different project requirements. Standard stile and rail construction is an option for wood units with aluminum units also available.

Lift-slide doors are available in multiple types of configurations including straight runs, curved radius patterns, corner opening groupings, and angled layouts. The panels can slide out of the way and be stacked on a jamb side, or the building can have a pocket designed into an adjacent wall to receive the panels and hide them from view when not being used. Retractable screens are the preferred way to allow for maximum ventilation and protection from insects.

CONCLUSION

Architects have a lot of choices when it comes to adding glazed fenestration into residential buildings. While standard windows may be a “go-to” solution, there are plenty of other ways to add large-format glazed products to a successful design. The type of glazing product selected can be based on size and functionality requirements but also on meeting particular design intentions. The performance of any of these products is based on understanding the nature of each type and reviewing the independent test data for structural integrity, water resistance, and energy performance. Working with manufacturers to understand their product offerings, capabilities and limitations can help create very satisfying residential designs that meet the needs of the owners, exceed minimum performance requirements, and stay within the established budget.

Peter J. Arsenault, FAIA, NCARB, LEED AP is a nationally known architect and a prolific author advancing positive acoustical experiences through better building design. www.pjaarch.com, www.linkedin.com/in/pjaarch